The initial symptoms of the disease includedfever and vomiting.[5] This was followed by formation ofulcers in the mouth and askin rash.[5] Over a number of days, the skin rash turned into the characteristic fluid-filledblisters with a dent in the center.[5] The bumps thenscabbed over and fell off, leaving scars.[5] The disease was transmitted from one person to another primarily through prolonged face-to-face contact with an infected person or rarely viacontaminated objects.[6][13][14] Prevention was achieved mainly through thesmallpox vaccine.[9] Once the disease had developed, certainantiviral medications could potentially have helped, but such medications did not become available until after the disease was eradicated.[9] The risk of death was about 30%, with higher rates among babies.[6][15] Often, those who survived had extensivescarring of their skin, and some were left blind.[6]
The earliest evidence of the disease dates to around 1500 BCE in Egyptianmummies.[16][17] The disease historically occurred inoutbreaks.[10] It was one of several diseases introduced by theColumbian exchange to theNew World, resulting inlarge swathes of Native Americans dying. In 18th-century Europe, it is estimated that 400,000 people died from the disease per year, and that one-third of all cases of blindness were due to smallpox.[10][18] Smallpox is estimated to have killed up to 300 million people in the 20th century[19][20] and around 500 million people in the last 100 years of its existence.[21] Earlier deaths included six Europeanmonarchs, includingLouis XV of France in 1774.[10][18] As recently as 1967, 15 million cases occurred a year.[10] The final known fatal caseoccurred in the United Kingdom in 1978.
Inoculation for smallpox appears to have started in China around the 1500s.[22][23] Europe adopted this practice from Asia in the first half of the 18th century.[24] In 1796,Edward Jenner introduced the modern smallpox vaccine.[25][26] In 1967, the WHO intensified efforts to eliminate the disease.[10] Smallpox is one of two infectious diseases to have been eradicated, the other beingrinderpest (a disease ofeven-toed ungulates) in 2011.[27][28] The term "smallpox" was first used in England in the 16th century to distinguish the disease fromsyphilis, which was then known as the "great pox".[29][30] Other historical names for the disease include pox, speckled monster, and red plague.[3][4][30]
The United States and Russia retain samples of variola virus in laboratories, which has sparkeddebates over safety.
Classification
Case fatality rate and frequency of smallpox by type and vaccination status according to Rao case study[31]
There are two forms of the smallpox.Variola major is the severe and most common form, with a more extensive rash and higher fever.Variola minor is a less common presentation, causing less severe disease, typically discrete smallpox, with historical death rates of 1% or less.[32] Subclinical (asymptomatic) infections with variola virus were noted but were not common.[33] In addition, a form calledvariola sine eruptione (smallpox without rash) was seen generally in vaccinated persons. This form was marked by a fever that occurred after the usualincubation period and could be confirmed only byantibody studies or, rarely, byviral culture.[33] In addition, there were two very rare and fulminating types of smallpox, the malignant (flat) and hemorrhagic forms, which were usually fatal.
The initial symptoms were similar to other viral diseases that are still extant, such asinfluenza and thecommon cold: fever of at least 38.3 °C (101 °F),muscle pain,malaise, headache and fatigue. As thedigestive tract was commonly involved, nausea, vomiting, and backache often occurred. The earlyprodromal stage usually lasted 2–4 days. By days 12–15, the first visible lesions – small reddish spots calledenanthem – appeared on mucous membranes of the mouth, tongue,palate, and throat, and the temperature fell to near-normal. These lesions rapidly enlarged and ruptured, releasing large amounts of virus into the saliva.[34]
Variola virus tended to attack skin cells, causing the characteristic pimples, ormacules, associated with the disease. A rash developed on the skin 24 to 48 hours after lesions on the mucous membranes appeared. Typically the macules first appeared on the forehead, then rapidly spread to the whole face,proximal portions of extremities, the trunk, and lastly todistal portions of extremities. The process took no more than 24 to 36 hours, after which no new lesions appeared.[34] At this point, variola major disease could take several very different courses, which resulted in four types of smallpox disease based on the Rao classification:[35] ordinary, modified, malignant (or flat), and hemorrhagic smallpox. Historically, ordinary smallpox had an overallfatality rate of about 30%, and the malignant and hemorrhagic forms were usually fatal. The modified form was almost never fatal. In early hemorrhagic cases, hemorrhages occurred before any skin lesions developed.[36] Theincubation period between contraction and the first obvious symptoms of the disease was 7–14 days.[37]
Ordinary
A child showing rash due to ordinary-type smallpox (variola major)
At least 90% of smallpox cases among unvaccinated persons were of the ordinary type.[33] In this form of the disease, by the second day of the rash the macules had become raisedpapules. By the third or fourth day, the papules had filled with an opalescent fluid to becomevesicles. This fluid becameopaque and turbid within 24–48 hours, resulting inpustules.
By the sixth or seventh day, all the skin lesions had become pustules. Between seven and ten days the pustules had matured and reached their maximum size. The pustules were sharply raised, typically round, tense, and firm to the touch. The pustules were deeply embedded in the dermis, giving them the feel of a small bead in the skin. Fluid slowly leaked from the pustules, and by the end of the second week, the pustules had deflated and began to dry up, forming crusts or scabs. By day 16–20 scabs had formed over all of the lesions, which had started to flake off, leavingdepigmented scars.[38]
Ordinary smallpox generally produced a discrete rash, in which the pustules stood out on the skin separately. The distribution of the rash was most dense on the face, denser on the extremities than on the trunk, and denser on the distal parts of the extremities than on the proximal. The palms of the hands and soles of the feet were involved in most cases.[33]
Confluent
Sometimes, the blisters merged into sheets, forming a confluent rash, which began to detach the outer layers of skin from the underlying flesh. Patients with confluent smallpox often remained ill even after scabs had formed over all the lesions. In one case series, the case-fatality rate in confluent smallpox was 62%.[33]
Modified
Modified smallpox in a vaccinated 4 year old inCardiff,Wales, 1962
Referring to the character of the eruption and the rapidity of its development, modified smallpox occurred mostly in previously vaccinated people. It was rare in unvaccinated people, with one case study showing 1–2% of modified cases compared to around 25% in vaccinated people. In this form, the prodromal illness still occurred but may have been less severe than in the ordinary type. There was usually no fever during the evolution of the rash. The skin lesions tended to be fewer and evolved more quickly, were more superficial, and may not have shown the uniform characteristic of more typical smallpox.[38] Modified smallpox was rarely, if ever, fatal. This form of variola major was more easily confused withchickenpox.[33]
Malignant
Malignant hemorrhagic smallpox in a baker during an 1896 epidemic inGloucester,England. Died 8 days after admission.
In malignant-type smallpox (also called flat smallpox) the lesions remained almost flush with the skin at the time when raised vesicles would have formed in the ordinary type. It is unknown why some people developed this type. Historically, it accounted for 5–10% of cases, and most (72%) were children.[3] Malignant smallpox was accompanied by a severeprodromal phase that lasted 3–4 days, prolonged high fever, and severe symptoms ofviremia. The prodromal symptoms continued even after the onset of the rash.[3] The rash on the mucous membranes (enanthem) was extensive. Skin lesions matured slowly, were typically confluent or semi-confluent, and by the seventh or eighth day, they were flat and appeared to be buried in the skin. Unlike ordinary-type smallpox, the vesicles contained little fluid, were soft and velvety to the touch, and may have contained hemorrhages. Malignant smallpox was nearly always fatal and death usually occurred between the 8th and 12th day of illness. Often, a day or two before death, the lesions turned ashen gray, which, along with abdominal distension, was a bad prognostic sign.[3] This form is thought to be caused by deficientcell-mediated immunity to smallpox. If the person recovered, the lesions gradually faded and did not form scars or scabs.[39]
Hemorrhagic
Hemorrhagic smallpox is a severe form accompanied by extensive bleeding into the skin, mucous membranes, gastrointestinal tract, andviscera. This form develops in approximately 2% of infections and occurs mostly in adults.[33] Pustules do not typically form in hemorrhagic smallpox. Instead, bleeding occurs under the skin, making it look charred and black,[33] hence this form of the disease is also referred to as variola nigra or "black pox".[40] Hemorrhagic smallpox has very rarely been caused by variola minor virus.[41] While bleeding may occur in mild cases and not affect outcomes,[42] hemorrhagic smallpox is typically fatal.[43] Vaccination does not appear to provide any immunity to either form of hemorrhagic smallpox and some cases even occurred among people that were revaccinated shortly before. It has two forms.[3]
Early
An unvaccinated person with probable hemorrhagic smallpox in a 1925Milwaukee, Wisconsin epidemic. He later died of the disease.
The early orfulminant form of hemorrhagic smallpox (referred to aspurpura variolosa) begins with a prodromal phase characterized by a high fever, severe headache, and abdominal pain.[39] The skin becomes dusky and erythematous, and this is rapidly followed by the development ofpetechiae and bleeding in the skin,conjunctiva and mucous membranes. Death often occurs suddenly between the fifth and seventh days of illness, when only a few insignificant skin lesions are present. Some people survive a few days longer, during which time the skin detaches and fluid accumulates under it, rupturing at the slightest injury. People are usually conscious until death or shortly before.[43] Autopsy revealspetechiae and bleeding in the spleen, kidney,serous membranes, skeletal muscles,pericardium, liver, gonads and bladder.[41] Historically, this condition was frequently misdiagnosed, with the correct diagnosis made only at autopsy.[41] This form is more likely to occur in pregnant women than in the general population (approximately 16% of cases in unvaccinated pregnant women were early hemorrhagic smallpox, versus roughly 1% in nonpregnant women and adult males).[43] The case fatality rate of early hemorrhagic smallpox approaches 100%.[43]
Late
There is also a later form of hemorrhagic smallpox (referred to late hemorrhagic smallpox, orvariolosa pustula hemorrhagica). The prodrome is severe and similar to that observed in early hemorrhagic smallpox, and the fever persists throughout the course of the disease.[3] Bleeding appears in the early eruptive period (but later than that seen inpurpura variolosa), and the rash is often flat and does not progress beyond the vesicular stage. Hemorrhages in the mucous membranes appear to occur less often than in the early hemorrhagic form.[33] Sometimes the rash forms pustules which bleed at the base and then undergo the same process as in ordinary smallpox. This form of the disease is characterized by a decrease in all of the elements of thecoagulation cascade and an increase in circulatingantithrombin.[34] This form of smallpox occurs anywhere from 3% to 25% of fatal cases, depending on the virulence of the smallpox strain.[36] Most people with the late-stage form die within eight to 10 days of illness. Among the few who recover, the hemorrhagic lesions gradually disappear after a long period of convalescence.[3] The case fatality rate for late hemorrhagic smallpox is around 90–95%.[35] Pregnant women are slightly more likely to experience this form of the disease, though not as much as early hemorrhagic smallpox.[3]
Cause
Variola virus
Thistransmission electron micrograph depicts a number of smallpoxvirions. The "dumbbell-shaped" structure inside the virion is the viral core, which contains the viral DNA; Mag. = ~370,000×
The date of the appearance of smallpox is not settled. It most probably evolved from a terrestrial African rodent virus between 68,000 and 16,000 years ago.[44] The wide range of dates is due to the different records used to calibrate themolecular clock. Oneclade was the variola major strains (the more clinically severe form of smallpox) which spread from Asia between 400 and 1,600 years ago. A second clade included both alastrim (a phenotypically mild smallpox) described from the American continents and isolates from West Africa which diverged from an ancestral strain between 1,400 and 6,300 years before present. This clade further diverged into two subclades at least 800 years ago.[45]
A second estimate has placed the separation of variola virus fromTaterapox (anOrthopoxvirus of some African rodents includinggerbils) at 3,000 to 4,000 years ago.[46] This is consistent with archaeological and historical evidence regarding the appearance of smallpox as a human disease which suggests a relatively recent origin. If the mutation rate is assumed to be similar to that of theherpesviruses, the divergence date of variola virus from Taterapox has been estimated to be 50,000 years ago.[46] While this is consistent with the other published estimates, it suggests that the archaeological and historical evidence is very incomplete. Better estimates of mutation rates in these viruses are needed.
Examination of a strain that dates fromc. 1650 found that this strain wasbasal to the other presently sequenced strains.[47] The mutation rate of this virus is well modeled by a molecular clock. Diversification of strains only occurred in the 18th and 19th centuries.
Four orthopoxviruses cause infection in humans: variola,vaccinia,cowpox, andmonkeypox. Variola virus infects only humans in nature, although primates and other animals have been infected in an experimental setting. Vaccinia, cowpox, and monkeypox viruses can infect both humans and other animals in nature.[33]
The life cycle of poxviruses is complicated by having multiple infectious forms, with differing mechanisms of cell entry. Poxviruses are unique among human DNA viruses in that they replicate in thecytoplasm of the cell rather than in thenucleus. To replicate, poxviruses produce a variety of specialized proteins not produced by otherDNA viruses, the most important of which is a viral-associatedDNA-dependent RNA polymerase.
Bothenveloped and unenvelopedvirions are infectious. The viral envelope is made of modifiedGolgi membranes containing viral-specific polypeptides, includinghemagglutinin.[49] Infection with either variola major virus or variola minor virus confers immunity against the other.[34]
The more common, infectious form of the disease was caused by the variola major virus strain, known for its significantly higher mortality rate compared to its counterpart, variola minor. Variola major had a fatality rate of around 30%, while variola minor’s mortality rate was about 1%. Throughout the 18th century, variola major was responsible for around 400,000 deaths annually in Europe alone. Survivors of the disease often faced lifelong consequences, such as blindness and severe scarring, which were nearly universal among those who recovered.[51]
In the first half of the 20th century, variola major was the primary cause of smallpox outbreaks across Asia and most of Africa. Meanwhile, variola minor was more commonly found in regions of Europe, North America, South America, and certain parts of Africa.[52]
Variola minor
Variola minor virus, also called alastrim, was a less common form of the virus, and much less deadly. Although variola minor had the same incubation period and pathogenetic stages as smallpox, it is believed to have had a mortality rate of less than 1%, as compared to variola major's 30%. Like variola major, variola minor was spread through inhalation of the virus in the air, which could occur through face-to-face contact or through fomites. Infection with variola minor virus conferred immunity against the more dangerous variola major virus.
Because variola minor was a less debilitating disease than smallpox, people were more frequently ambulant and thus able to infect others more rapidly. As such, variola minor swept through the United States, Great Britain, and South Africa in the early 20th century, becoming the dominant form of the disease in those areas and thus rapidly decreasing mortality rates. Along with variola major, the minor form has now been totally eradicated from the globe. The last case of indigenous variola minor was reported in a Somali cook,Ali Maow Maalin, in October 1977, and smallpox was officially declared eradicated worldwide in May 1980.[16] Variola minor was also called white pox, kaffir pox, Cuban itch, West Indian pox, milk pox, and pseudovariola.
Genome composition
Thegenome of variola major virus is about 186,000 base pairs in length.[53] It is made from linear double strandedDNA and contains thecoding sequence for about 200genes.[54] The genes are usually not overlapping and typically occur in blocks that point towards the closer terminal region of the genome.[55] The coding sequence of the central region of the genome is highly consistent acrossorthopoxviruses, and the arrangement of genes is consistent across chordopoxviruses.[54][55]
The center of the variola virus genome contains the majority of the essential viral genes, including the genes for structuralproteins,DNA replication,transcription, andmRNA synthesis.[54] The ends of the genome vary more across strains and species oforthopoxviruses.[54] These regions contain proteins thatmodulate the hosts' immune systems, and are primarily responsible for the variability invirulence across theorthopoxvirus family.[54] These terminal regions in poxviruses areinverted terminal repetitions (ITR) sequences.[55] These sequences are identical but oppositely oriented on either end of the genome, leading to the genome being a continuous loop of DNA.[55] Components of the ITR sequences include an incompletely base paired A/T richhairpin loop, a region of roughly 100 base pairs necessary for resolvingconcatomeric DNA (a stretch of DNA containing multiple copies of the same sequence), a fewopen reading frames, andshort tandemly repeating sequences of varying number and length.[55] The ITRs ofpoxviridae vary in length across strains and species.[55] The coding sequence for most of the viral proteins in variola major virus have at least 90% similarity with the genome ofvaccinia, a related virus used forvaccination against smallpox.[55]
Gene expression
Gene expression of variola virus occurs entirely within thecytoplasm of the hostcell, and follows a distinct progression during infection.[55] After entry of an infectiousvirion into a host cell, synthesis of viralmRNA can be detected within 20 minutes.[55] About half of the viral genome istranscribed prior to thereplication of viral DNA.[55] The first set of expressed genes are transcribed by pre-existing viral machinery packaged within the infecting virion.[55] These genes encode the factors necessary for viral DNA synthesis and for transcription of the next set of expressed genes.[55] Unlike most DNA viruses,DNA replication in variola virus and other poxviruses takes place within the cytoplasm of the infected cell.[55] The exact timing of DNA replication after infection of a host cell varies across thepoxviridae.[55]Recombination of the genome occurs within actively infected cells.[55] Following the onset of viral DNA replication, an intermediate set of genes codes fortranscription factors of late gene expression.[55] Theproducts of the later genes include transcription factors necessary for transcribing the early genes for new virions, as well as viralRNA polymerase and other essential enzymes for new viral particles.[55] These proteins are then packaged into new infectious virions capable of infecting other cells.[55]
Research
Two live samples of variola major virus remain, one in the United States at theCDC in Atlanta, and one at theVector Institute in Koltsovo, Russia.[56] Research with the remaining virus samples is tightly controlled, and each research proposal must be approved by theWHO and theWorld Health Assembly (WHA).[56] Most research on poxviruses is performed using the closely relatedVaccinia virus as a model organism.[55] Vaccinia virus, which is used to vaccinate for smallpox, is also under research as aviral vector forvaccines for unrelated diseases.[57]
The genome of variola major virus was firstsequenced in its entirety in the 1990s.[54] The complete coding sequence is publicly available online. The currentreference sequence for variola major virus was sequenced from a strain that circulated in India in 1967. In addition, there are sequences for samples of other strains that were collected during the WHO eradication campaign.[54] Agenome browser for a complete database of annotated sequences of variola virus and other poxviruses is publicly available through theViral Bioinformatics Resource Center.[58]
Genetic engineering
TheWHO currently bansgenetic engineering of the variola virus.[59] However, in 2004, a committee advisory to the WHO voted in favor of allowing editing of the genome of the two remaining samples of variola major virus to add amarker gene.[59] This gene, calledGFP, or green fluorescent protein, would cause live samples of the virus to glow green under fluorescent light.[60] The insertion of this gene, which would not influence thevirulence of the virus, would be the only allowed modification of the genome.[60] The committee stated the proposed modification would aid in research of treatments by making it easier to assess whether a potential treatment was effective in killing viral samples.[60] The recommendation could only take effect if approved by theWHA.[60] When the WHA discussed the proposal in 2005, it refrained from taking a formal vote on the proposal, stating that it would review individual research proposals one at a time.[61] Addition of the GFP gene to theVaccinia genome is routinely performed during research on the closely relatedVaccinia virus.[62]
Controversies
The public availability of the variola virus complete sequence has raised concerns about the possibility of illicit synthesis of infectious virus.[63]Vaccinia, a cousin of the variola virus, was artificially synthesized in 2002 byNIH scientists.[64] They used a previously established method that involved using arecombinant viral genome to create a self-replicating bacterialplasmid that produced viral particles.[64]
In 2016, another group synthesized thehorsepox virus using publicly available sequence data for horsepox.[65] The researchers argued that their work would be beneficial to creating a safer and more effectivevaccine for smallpox, although an effective vaccine is already available.[65] The horsepox virus had previously seemed to have gone extinct, raising concern about potential revival of variola major and causing other scientists to question their motives.[63] Critics found it especially concerning that the group was able to recreate viable virus in a short time frame with relatively little cost or effort.[65] Although the WHO bans individual laboratories fromsynthesizing more than 20% of the genome at a time, and purchases of smallpox genome fragments are monitored and regulated, a group withmalicious intentions could compile, from multiple sources, the full synthetic genome necessary to produce viable virus.[65]
Transmission
Smallpox was highly contagious, but generally spread more slowly and less widely than some other viral diseases, perhaps because transmission required close contact and occurred after the onset of the rash. The overall rate of infection was also affected by the short duration of the infectious stage. Intemperate areas, the number of smallpox infections was highest during the winter and spring. In tropical areas, seasonal variation was less evident and the disease was present throughout the year.[33] Age distribution of smallpox infections depended onacquired immunity.Vaccinationimmunity declined over time and was probably lost within thirty years.[34] Smallpox was not known to be transmitted by insects or animals and there was noasymptomatic carrier state.[33]
Transmission occurred through inhalation ofairborne variola virus, usually droplets expressed from the oral, nasal, orpharyngealmucosa of an infected person. It was transmitted from one person to another primarily through prolonged face-to-face contact with an infected person.[14]
Some infections of laundry workers with smallpox after handling contaminated bedding suggested that smallpox could be spread through direct contact with contaminated objects (fomites), but this was found to be rare.[14][35] Also rarely, smallpox was spread by virus carried in the air in enclosed settings such as buildings, buses, and trains.[32] The virus can cross theplacenta, but the incidence ofcongenital smallpox was relatively low.[34] Smallpox was not notably infectious in theprodromal period and viral shedding was usually delayed until the appearance of the rash, which was often accompanied bylesions in the mouth and pharynx. The virus can be transmitted throughout the course of the illness, but this happened most frequently during the first week of the rash when most of the skin lesions were intact.[33] Infectivity waned in 7 to 10 days when scabs formed over the lesions, but the infected person was contagious until the last smallpox scab fell off.[66]
Concern about possible use of smallpox for biological warfare led in 2002 to Donald K. Milton's detailed review of existing research on its transmission and of then-current recommendations for controlling its spread. He agreed, citing Rao,Fenner and others, that “careful epidemiologic investigation rarely implicated fomites as a source of infection”; noted that “Current recommendations for control of secondary smallpox infections emphasize transmission ‘by expelled droplets to close contacts (those within 6–7 feet)’”; but warned that the “emphasis on spread via large droplets may reduce the vigilance with which more difficult airborne precautions [i.e. against finer droplets capable of traveling longer distances and penetrating deeply into the lower respiratory tract] are maintained”.[67]
Mechanism
Once inhaled, the variola virus invaded the mucous membranes of the mouth, throat, and respiratory tract. From there, it migrated to regionallymph nodes and began to multiply. In the initial growth phase, the virus seemed to move from cell to cell, but by around the 12th day, widespreadlysis of infected cells occurred and the virus could be found in the bloodstream in large numbers, a condition known asviremia. This resulted in the second wave of multiplication in thespleen,bone marrow, and lymph nodes.
Diagnosis
The clinical definition of ordinary smallpox is an illness with acute onset of fever equal to or greater than 38.3 °C (101 °F) followed by a rash characterized by firm, deep-seated vesicles or pustules in the same stage of development without other apparent cause.[33] When a clinical case was observed, smallpox was confirmed using laboratory tests.
Microscopically, poxviruses produce characteristiccytoplasmicinclusion bodies, the most important of which are known asGuarnieri bodies, and are the sites ofviral replication. Guarnieri bodies are readily identified in skin biopsies stained with hematoxylin and eosin, and appear as pink blobs. They are found in virtually all poxvirus infections but the absence of Guarnieri bodies could not be used to rule out smallpox.[68] The diagnosis of an orthopoxvirus infection can also be made rapidly byelectron microscopic examination of pustular fluid or scabs. All orthopoxviruses exhibit identical brick-shapedvirions by electron microscopy.[34] If particles with the characteristic morphology ofherpesviruses are seen this will eliminate smallpox and other orthopoxvirus infections.
Chickenpox was commonly confused with smallpox in the immediate post-eradication era. Chickenpox and smallpox could be distinguished by several methods. Unlike smallpox, chickenpox does not usually affect the palms and soles. Additionally, chickenpox pustules are of varying size due to variations in the timing of pustule eruption: smallpox pustules are all very nearly the same size since the viral effect progresses more uniformly. A variety of laboratory methods were available for detecting chickenpox in the evaluation of suspected smallpox cases.[33]
The earliest procedure used to prevent smallpox wasinoculation withvariola minor virus (a method later known asvariolation after the introduction ofsmallpox vaccine to avoid possible confusion), which likely occurred in India, Africa, and China well before the practice arrived in Europe.[15] The idea that inoculation originated in India has been challenged, as few of the ancientSanskrit medical texts described the process of inoculation.[71] Accounts of inoculation against smallpox in China can be found as early as the late 10th century, and the procedure was widely practiced by the 16th century, during theMing dynasty.[72] If successful, inoculation produced lastingimmunity to smallpox. Because the person was infected with variola virus, a severe infection could result, and the person could transmit smallpox to others. Variolation had a 0.5–2 percent mortality rate, considerably less than the 20–30 percent mortality rate of smallpox.[33] Two reports on the Chinese practice ofinoculation were received by theRoyal Society in London in 1700; one by Dr.Martin Lister who received a report by an employee of theEast India Company stationed in China and another byClopton Havers.[73]
Lady Mary Wortley Montagu observed smallpox inoculation during her stay in theOttoman Empire, writing detailed accounts of the practice in her letters, and enthusiastically promoted the procedure in England upon her return in 1718.[74] According toVoltaire (1742), the Turks derived their use of inoculation from neighbouringCircassia. Voltaire does not speculate on where the Circassians derived their technique from, though he reports that the Chinese have practiced it "these hundred years".[75] In 1721,Cotton Mather and colleagues provoked controversy in Boston by inoculating hundreds. After publishingThe present method of inoculating for the small-pox in 1767,Dr Thomas Dimsdale was invited to Russia to variolate the EmpressCatherine the Great of Russia and her son,Grand Duke Paul, which he successfully did in 1768. In 1796,Edward Jenner, a doctor inBerkeley, Gloucestershire, rural England, discovered that immunity to smallpox could be produced by inoculating a person with material from a cowpox lesion. Cowpox is a poxvirus in the same family as variola. Jenner called the material used for inoculation vaccine from theroot wordvacca, which is Latin for cow. The procedure was much safer than variolation and did not involve a risk of smallpox transmission. Vaccination to prevent smallpox was soon practiced all over the world. During the 19th century, the cowpox virus used for smallpox vaccination was replaced by the vaccinia virus. Vaccinia is in the same family as cowpox and variola virus but is genetically distinct from both. The origin of the vaccinia virus and how it came to be in the vaccine are not known.[33]
An 1802 cartoon byJames Gillray of the early controversy surroundingEdward Jenner's vaccination procedure, showing using his cowpox-derivedsmallpox vaccine causing cattle to emerge from patients
The current formulation of the smallpox vaccine is a live virus preparation of the infectious vaccinia virus. The vaccine is given using abifurcated (two-pronged) needle that is dipped into the vaccine solution. The needle is used to prick the skin (usually the upper arm) several times in a few seconds. If successful, a red and itchy bump develops at the vaccine site in three or four days. In the first week, the bump becomes a large blister (called a "Jennerian vesicle") which fills with pus and begins to drain. During the second week, the blister begins to dry up, and a scab forms. The scab falls off in the third week, leaving a small scar.[76]
Theantibodies induced by the vaccinia vaccine are cross-protective for other orthopoxviruses, such as monkeypox, cowpox, and variola (smallpox) viruses. Neutralizing antibodies are detectable 10 days after first-time vaccination and seven days after revaccination. Historically, the vaccine has been effective in preventing smallpox infection in 95 percent of those vaccinated.[77] Smallpox vaccination provides a high level of immunity for three to five years and decreasing immunity thereafter. If a person is vaccinated again later, the immunity lasts even longer. Studies of smallpox cases in Europe in the 1950s and 1960s demonstrated that the fatality rate among persons vaccinated less than 10 years before exposure was 1.3 percent; it was 7 percent among those vaccinated 11 to 20 years prior, and 11 percent among those vaccinated 20 or more years before infection. By contrast, 52 percent of unvaccinated persons died.[78]
A demonstration by medical personnel on use of a bifurcated needle to deliver the smallpox vaccine, 2002
There are side effects and risks associated with the smallpox vaccine. In the past, about 1 out of 1,000 people vaccinated for the first time experienced serious, but non-life-threatening, reactions, including toxic orallergic reaction at the site of the vaccination (erythema multiforme), spread of the vaccinia virus to other parts of the body, and spread to other individuals. Potentially life-threatening reactions occurred in 14 to 500 people out of every 1 million people vaccinated for the first time. Based on past experience, it is estimated that 1 or 2 people in 1 million (0.000198 percent) who receive the vaccine may die as a result, most often the result of postvaccinialencephalitis or severenecrosis in the area of vaccination (calledprogressive vaccinia).[77]
Given these risks, as smallpox became effectively eradicated and the number of naturally occurring cases fell below the number of vaccine-induced illnesses and deaths, routine childhood vaccination was discontinued in the United States in 1972 and was abandoned in most European countries in the early 1970s.[10][79] Routine vaccination of health care workers was discontinued in the U.S. in 1976, and among military recruits in 1990 (although military personnel deploying to the Middle East and Korea still receive the vaccination[80]). By 1986, routine vaccination had ceased in all countries.[10] It is now primarily recommended for laboratory workers at risk for occupational exposure.[33] However, the possibility of variola virus being used as a biological weapon has rekindled interest in the development of newer vaccines.[81] The smallpox vaccine is also effective in, and therefore administered for, the prevention ofmpox.[82]
ACAM2000 is asmallpox vaccine developed by Acambis, approved for use in the United States by theU.S. FDA on August 31, 2007. It contains livevaccinia virus, cloned from the same strain used in an earliervaccine,Dryvax. While the Dryvax virus was cultured in the skin of calves and freeze-dried, ACAM2000s virus is cultured in kidney epithelial cells (Vero cells) from anAfrican green monkey. Efficacy and adverse reaction incidence are similar to Dryvax.[81] The vaccine is not routinely available to the US public; it is, however, used in the military and maintained in theStrategic National Stockpile.[83]
Treatment
Smallpox vaccination within three days of exposure will prevent or significantly lessen the severity of smallpox symptoms in the vast majority of people. Vaccination four to seven days after exposure can offer some protection from disease or may modify the severity of the disease.[77] Other than vaccination, treatment of smallpox is primarily supportive, such as wound care and infection control, fluid therapy, and possibleventilator assistance. Flat and hemorrhagic types of smallpox are treated with the same therapies used to treatshock, such asfluid resuscitation. People with semi-confluent and confluent types of smallpox may have therapeutic issues similar to patients with extensive skinburns.[84]
Antiviral treatments have improved since the last large smallpox epidemics, and as of 2004, studies suggested that the antiviral drugcidofovir might be useful as a therapeutic agent. The drug must be administeredintravenously, and may cause seriouskidney toxicity.[85] In July 2018, theFood and Drug Administration approvedtecovirimat, the first drug approved for treatment of smallpox.[86] However, during treatment viral mutations causing resistance have been known to occur, especially since its use in the2022–2023 mpox outbreak which jeopardize its effectiveness for smallpox biothreat preparedness.[87]
In June 2021,brincidofovir was approved for medical use in the United States for the treatment of human smallpox disease caused by variola virus.[88][89]
Prognosis
Smallpox survivor with facial scarring, blindness and whitecorneal scar in his left eye, 1972
The mortality rate from variola minor is approximately 1%, while the mortality rate from variola major is approximately 30%.[90]
Ordinary type-confluent is fatal about 50–75% of the time, ordinary-type semi-confluent about 25–50% of the time, in cases where the rash is discrete the case-fatality rate is less than 10%. The overall fatality rate for children younger than 1 year of age is 40–50%. Hemorrhagic and flat types have the highest fatality rates. The fatality rate for flat or late hemorrhagic type smallpox is 90% or greater and nearly 100% is observed in cases of early hemorrhagic smallpox.[43] The case-fatality rate for variola minor is 1% or less.[38] There is no evidence of chronic or recurrent infection with variola virus.[38] In cases of flat smallpox in vaccinated people, the condition was extremely rare but less lethal, with one case series showing a 67% death rate.[3]
In fatal cases of ordinary smallpox, death usually occurs between days 10–16 of the illness. The cause of death from smallpox is not clear, but the infection is now known to involve multiple organs. Circulatingimmune complexes, overwhelming viremia, or an uncontrolledimmune response may be contributing factors.[33] In early hemorrhagic smallpox, death occurs suddenly about six days after the fever develops. The cause of death in early hemorrhagic cases is commonly due to heart failure andpulmonary edema. In late hemorrhagic cases, high and sustained viremia, severeplatelet loss and poor immune response were often cited as causes of death.[3] In flat smallpox modes of death are similar to those in burns, withloss of fluid, protein andelectrolytes, and fulminatingsepsis.[84]
Complications
Complications of smallpox arise most commonly in the respiratory system and range from simplebronchitis to fatalpneumonia. Respiratory complications tend to develop on about the eighth day of the illness and can be either viral or bacterial in origin. Secondary bacterial infection of the skin is a relatively uncommon complication of smallpox. When this occurs, the fever usually remains elevated.[33]
Other complications includeencephalitis (1 in 500 patients), which is more common in adults and may cause temporary disability; permanent pitted scars, most notably on the face; and complications involving the eyes (2% of all cases). Pustules can form on the eyelid,conjunctiva, andcornea, leading to complications such asconjunctivitis,keratitis,corneal ulcer,iritis,iridocyclitis, and atrophy of the optic nerve. Blindness results in approximately 35–40% of eyes affected with keratitis and corneal ulcer. Hemorrhagic smallpox can cause subconjunctival andretinal hemorrhages. In 2–5% of young children with smallpox, virions reach the joints and bone, causingosteomyelitis variolosa. Bony lesions are symmetrical, most common in the elbows, legs, and characteristically cause separation of theepiphysis and markedperiosteal reactions. Swollen joints limit movement, and arthritis may lead to limb deformities,ankylosis, malformed bones, flail joints, and stubby fingers.[34]
Between 65 and 80% of survivors are marked with deep pitted scars (pockmarks), most prominent on the face.
Statue ofSopona, theYoruba god thought to cause the disease
The earliest credible clinical evidence of smallpox is found in the descriptions of smallpox-like disease in medical writings from ancient India (as early as 1500 BCE),[91][92] and China (1122 BCE),[93] as well as a study of theEgyptianmummy ofRamses V (died 1145 BCE).[92][94] It has been speculated that Egyptian traders brought smallpox to India during the 1st millennium BCE, where it remained as anendemic human disease for at least 2000 years. Smallpox was probably introduced into China during the 1st century CE from the southwest, and in the 6th century was carried from China to Japan.[3] In Japan, theepidemic of 735–737 is believed to have killed as much as one-third of the population.[18][95] At least seven religious deities have been specifically dedicated to smallpox, such as the godSopona in theYoruba religion in West Africa. In India, the Hindu goddess of smallpox,Shitala, was worshipped in temples throughout the country.[96]
A different viewpoint is that smallpox emerged 1588 CE and the earlier reported cases were incorrectly identified as smallpox.[97][47]
The timing of the arrival of smallpox in Europe and south-western Asia is less clear. Smallpox is not clearly described in either theOld orNew Testaments of the Bible or in the literature of the Greeks or Romans. While some have identified thePlague of Athens – which was said to have originated in "Ethiopia" and Egypt – or the plague that lifted Carthage's 396 BCEsiege of Syracuse – with smallpox,[3] many scholars agree it is very unlikely such a serious disease as variola major would have escaped being described byHippocrates if it had existed in the Mediterranean region during his lifetime.[42]
While theAntonine Plague that swept through theRoman Empire in 165–180 CE may have been caused by smallpox,[98] SaintNicasius of Rheims became the patron saint of smallpox victims for having supposedly survived a bout in 450,[3] and SaintGregory of Tours recorded a similar outbreak in France and Italy in 580, the first use of the termvariola.[3] Other historians speculate thatArab armies first carried smallpox from Africa into Southwestern Europe during the 7th and 8th centuries.[3] In the 9th century thePersian physician,Rhazes, provided one of the most definitive descriptions of smallpox and was the first to differentiate smallpox frommeasles andchickenpox in hisKitab fi al-jadari wa-al-hasbah (The Book of Smallpox and Measles).[99] During theMiddle Ages several smallpox outbreaks occurred in Europe. However, smallpox had not become established there until the population growth and mobility marked by theCrusades allowed it to do so. By the 16th century, smallpox had become entrenched across most of Europe,[3] where it had a mortality rate as high as 30 percent. This endemic occurrence of smallpox in Europe is of particular historical importance, as successive exploration and colonization by Europeans tended to spread the disease to other nations. By the 16th century, smallpox had become a predominant cause of morbidity and mortality throughout much of the world.[3]
Drawing accompanying text in Book XII of the 16th-centuryFlorentine Codex (compiled 1555–1576), showingNahuas of conquest-era central Mexico with smallpox
There were no credible descriptions of smallpox-like disease in theAmericas before the westward exploration by Europeans in the 15th century CE.[45] Smallpox was introduced into the Caribbean island ofHispaniola in 1507, and into the mainland in 1520, when Spanish settlers from Hispaniola arrived in Mexico, inadvertently carrying smallpox with them. Because the nativeAmerindian population had no acquired immunity to this new disease, their peoples were decimated by epidemics. Such disruption and population losses were an important factor in the Spanish achieving conquest of theAztecs and theIncas.[3] Similarly, English settlement of the east coast of North America in 1633 inPlymouth, Massachusetts was accompanied by devastating outbreaks of smallpox among Native American populations,[100] and subsequently among the native-born colonists.[101] Case fatality rates during outbreaks in Native American populations were as high as 90%.[102] Smallpox was introduced intoAustralia in 1789 and again in 1829,[3] though colonial surgeons, who by 1829 were attempting to distinguish between smallpox andchickenpox (which could be almost equally fatal to Aborigines), were divided as to whether the 1829–1830 epidemic was chickenpox or smallpox.[103] Although smallpox was never endemic on the continent,[3] it has been described as the principal cause of death inAboriginal populations between 1780 and 1870.[104]
Global number of reported smallpox cases from 1920 to 2016Gravestone from 1711 for 4 children who died of smallpox (Rastede, Germany)
By the mid-18th century, smallpox was a majorendemic disease everywhere in the world except in Australia and small islands untouched by outside exploration. In 18th century Europe, smallpox was a leading cause of death, killing an estimated 400,000 Europeans each year.[105] Up to 10 percent ofSwedish infants died of smallpox each year,[18] and the death rate of infants inRussia might have been even higher.[93] The widespread use ofvariolation in a few countries, notably Great Britain, its North American colonies, and China, somewhat reduced the impact of smallpox among the wealthy classes during the latter part of the 18th century, but a real reduction in its incidence did not occur until vaccination became a common practice toward the end of the 19th century. Improved vaccines and the practice of re-vaccination led to a substantial reduction in cases in Europe and North America, but smallpox remained almost unchecked everywhere else in the world. By the mid-20th century, variola minor occurred along with variola major, in varying proportions, in many parts of Africa. Patients with variola minor experience only a mild systemic illness, are oftenambulant throughout the course of the disease, and are therefore able to more easily spread disease. Infection with variola minor virus induces immunity against the more deadly variola major form. Thus, as variola minor spread all over the US, into Canada, the South American countries, and Great Britain, it became the dominant form of smallpox, further reducing mortality rates.[3]
Decade in which smallpox ceased to beendemic by country
The first clear reference to smallpox inoculation was made by the Chinese authorWan Quan (1499–1582) in hisDòuzhěn xīnfǎ (痘疹心法, "Pox Rash Teachings") published in 1549,[106] with earliest hints of the practice in China during the 10th century.[107] In China, powdered smallpox scabs were blown up the noses of the healthy. People would then develop a mild case of the disease and from then on were immune to it. The technique did have a 0.5–2.0% mortality rate, but that was considerably less than the 20–30% mortality rate of the disease itself. Two reports on the Chinese practice ofinoculation were received by theRoyal Society in London in 1700: one by Dr.Martin Lister who received a report by an employee of theEast India Company stationed in China and another byClopton Havers.[108]Voltaire (1742) reports that the Chinese had practiced smallpox inoculation "these hundred years".[75]Variolation had also been witnessed inTurkey byLady Mary Wortley Montagu, who later introduced it in the UK.[109]
An early mention of the possibility of smallpox's eradication was made in reference to the work ofJohnnie Notions, a self-taught inoculator fromShetland, Scotland. Notions found success in treating people from at least the late 1780s through a method devised by himself despite having no formal medical background.[110][111] His method involved exposing smallpox pus topeat smoke, burying it in the ground withcamphor for up to 8 years, and then inserting the matter into a person's skin using a knife, and covering the incision with a cabbage leaf.[112] He was reputed not to have lost a single patient.[112]Arthur Edmondston, in writings on Notions' technique that were published in 1809, stated, "Had every practitioner been as uniformly successful in the disease as he was, the small-pox might have been banished from the face of the earth, without injuring the system, or leaving any doubt as to the fact."[113]
Vaccination during the Smallpox Eradication and Measles Control Program inNiger, 1969
The English physicianEdward Jenner demonstrated the effectiveness of cowpox to protect humans from smallpox in 1796, after which various attempts were made to eliminate smallpox on a regional scale. In Russia in 1796, the first child to receive this treatment was bestowed the name "Vaccinov" byCatherine the Great, and was educated at the expense of the nation.[114]
The introduction of the vaccine to the New World took place inTrinity, Newfoundland in 1800 byDr. John Clinch, boyhood friend and medical colleague of Jenner.[115] As early as 1803, the Spanish Crown organized theBalmis expedition to transport the vaccine to theSpanish colonies in the Americas and the Philippines, and establish mass vaccination programs there.[116] TheU.S. Congress passed theVaccine Act of 1813 to ensure that safe smallpox vaccine would be available to the American public. By about 1817, a robust state vaccination program existed in theDutch East Indies.[117]
On March 26, 1806, theSwiss cantonThurgau became the first state in the world to introduce compulsory smallpox vaccinations, by order of the cantonal councillorJakob Christoph Scherb.[118][119] Half a year later,Elisa Bonaparte issued a corresponding order for herPrincipality of Lucca and Piombino.[120]Baden followed in 1809,Prussia in 1815,Württemberg in 1818,Sweden in 1816 and theGerman Empire in 1874 through the Reichs Vaccination Act.[121][122] In Lutheran Sweden, the Protestant clergy played a pioneering role in voluntary smallpox vaccination as early as 1800.[123] The first vaccination was carried out in Liechtenstein in 1801, and from 1812 it was mandatory to vaccinate.[124]
InBritish India a program was launched to propagate smallpox vaccination, through Indian vaccinators, under the supervision of European officials.[125] Nevertheless, British vaccination efforts in India, and inBurma in particular, were hampered by indigenous preference for inoculation and distrust of vaccination, despite tough legislation, improvements in the local efficacy of the vaccine and vaccine preservative, and education efforts.[126] By 1832, the federal government of the United States established a smallpox vaccination program forNative Americans.[127] In 1842, the United Kingdom banned inoculation, later progressing tomandatory vaccination. The British government introduced compulsory smallpox vaccination by an Act of Parliament in 1853.[128]
In the United States, from 1843 to 1855, firstMassachusetts and then other states required smallpox vaccination. Although some disliked these measures,[93] coordinated efforts against smallpox went on, and the disease continued to diminish in the wealthy countries. In Northern Europe a number of countries had eliminated smallpox by 1900, and by 1914, the incidence in most industrialized countries had decreased to comparatively low levels.
Vaccination continued in industrialized countries as protection against reintroduction until the mid to late 1970s.Australia andNew Zealand are two notable exceptions; neither experienced endemic smallpox and never vaccinated widely, relying instead on protection by distance and strict quarantines.[129]
The firsthemisphere-wide effort to eradicate smallpox was made in 1950 by thePan American Health Organization.[130] The campaign was successful in eliminating smallpox from all countries of the Americas except Argentina, Brazil, Colombia, and Ecuador.[129] In 1958 ProfessorViktor Zhdanov, Deputy Minister of Health for theUSSR, called on theWorld Health Assembly to undertake a global initiative toeradicate smallpox.[131] The proposal (Resolution WHA11.54) was accepted in 1959.[131] At this point, 2 million people were dying from smallpox every year. Overall, the progress towards eradication was disappointing, especially in Africa and in theIndian subcontinent. In 1966 an international team, the Smallpox Eradication Unit, was formed under the leadership of an American,Donald Henderson.[131] In 1967, the World Health Organization intensified the global smallpox eradication by contributing $2.4 million annually to the effort, and adopted the newdisease surveillance method promoted by Czech epidemiologistKarel Raška.[132]
Three-year-oldRahima Banu of Bangladesh(pictured) was the last person infected with naturally occurring variola major, in 1975.
In the early 1950s, an estimated 50 million cases of smallpox occurred in the world each year.[10] To eradicate smallpox, each outbreak had to be stopped from spreading, by isolation of cases and vaccination of everyone who lived close by.[133] This process is known as "ring vaccination". The key to this strategy was the monitoring of cases in a community (known as surveillance) and containment.
The initial problem the WHO team faced was inadequate reporting of smallpox cases, as many cases did not come to the attention of the authorities. The fact that humans are the only reservoir for smallpox infection (the virus only infected humans and not other animals) and thatcarriers did not exist played a significant role in the eradication of smallpox. The WHO established a network of consultants who assisted countries in setting up surveillance and containment activities. Early on, donations of vaccine were provided primarily by the Soviet Union and the United States, but by 1973, more than 80 percent of all vaccine was produced in developing countries.[129] The Soviet Union provided one and a half billion doses between 1958 and 1979, as well as the medical staff.[134]
The last major European outbreak of smallpox was in1972 in Yugoslavia, after a pilgrim fromKosovo returned from the Middle East, where he had contracted the virus. The epidemic infected 175 people, causing 35 deaths. Authorities declaredmartial law, enforced quarantine, and undertook widespread re-vaccination of the population, enlisting the help of the WHO. In two months, the outbreak was over.[135] Prior to this, there had been a smallpox outbreak in May–July 1963 inStockholm, Sweden, brought from theFar East by a Swedish sailor; this had been dealt with by quarantine measures and vaccination of the local population.[136]
Bifurcated needle used in the WHO's smallpox eradication program[137]
By the end of 1975, smallpox persisted only in theHorn of Africa. Conditions were very difficult inEthiopia andSomalia, where there were few roads. Civil war, famine, and refugees made the task even more difficult. An intensive surveillance, containment, and vaccination program was undertaken in these countries in early and mid-1977, under the direction of Australian microbiologistFrank Fenner. As the campaign neared its goal, Fenner and his team played an important role in verifying eradication.[138] The last naturally occurring case of indigenous smallpox (Variola minor) was diagnosed inAli Maow Maalin, a hospital cook in Merca,Somalia, on 26 October 1977.[33] The last naturally occurring case of the more deadlyVariola major had been detected in October 1975 in a three-year-oldBangladeshi girl,Rahima Banu.[40]
The global eradication of smallpox was certified, based on intense verification activities, by a commission of eminent scientists on 9 December 1979 and subsequently endorsed by the World Health Assembly on 8 May 1980.[10][139] The first two sentences of the resolution read:
Having considered the development and results of the global program on smallpox eradication initiated by WHO in 1958 and intensified since 1967 … Declares solemnly that the world and its peoples have won freedom from smallpox, which was a most devastating disease sweeping in epidemic form through many countries since earliest time, leaving death, blindness and disfigurement in its wake and which only a decade ago was rampant in Africa, Asia and South America.[140]
Costs and benefits
The cost of the eradication effort, from 1967 to 1979, was roughly US$300 million. Roughly a third came from the developed world, which had largely eradicated smallpox decades earlier. The United States, the largest contributor to the program, has reportedly recouped that investment every 26 days since in money not spent on vaccinations and the costs of incidence.[141]
WHO first recommended destruction of the virus in 1986 and later set the date of destruction to be 30 December 1993. This was postponed to 30 June 1999.[146] Due to resistance from the U.S. and Russia, in 2002 the World Health Assembly agreed to permit the temporary retention of the virus stocks for specific research purposes.[147] Destroying existing stocks would reduce the risk involved with ongoing smallpox research; the stocks are not needed to respond to a smallpox outbreak.[148] Some scientists have argued that the stocks may be useful in developing new vaccines, antiviral drugs, and diagnostic tests;[149] a 2010 review by a team of public health experts appointed by WHO concluded that no essential public health purpose is served by the U.S. and Russia continuing to retain virus stocks.[150] The latter view is frequently supported in the scientific community, particularly among veterans of the WHO Smallpox Eradication Program.[151]
On March 31, 2003, smallpoxscabs were found inside an envelope in an 1888 book onCivil War medicine inSanta Fe, New Mexico.[152] The envelope was labeled as containing scabs from a vaccination and gave scientists at the CDC an opportunity to study the history of smallpox vaccination in the United States.
On July 1, 2014, six sealed glass vials of smallpox dated 1954, along with sample vials of other pathogens, were discovered in a cold storage room in an FDA laboratory at theNational Institutes of Health location inBethesda, Maryland. The smallpox vials were subsequently transferred to the custody of the CDC in Atlanta, where virus taken from at least two vials proved viable in culture.[153][154] After studies were conducted, the CDC destroyed the virus under WHO observation on February 24, 2015.[155]
In 2017, scientists at theUniversity of Alberta recreated an extincthorse pox virus to demonstrate that the variola virus can be recreated in a small lab at a cost of about $100,000, by a team of scientists without specialist knowledge.[156] This makes the retention controversy irrelevant since the virus can be easily recreated even if all samples are destroyed. Although the scientists performed the research to help development of new vaccines as well as trace smallpox's history, the possibility of the techniques being used for nefarious purposes was immediately recognized, raising questions ondual use research and regulations.[157][158]
In September 2019, the Russian lab housing smallpox samples experienced a gas explosion that injured one worker. It did not occur near the virus storage area, and no samples were compromised, but the incident prompted a review of risks to containment.[159]
Society and culture
Biological warfare
In 1763,Pontiac's War broke out as aNative American confederacy led byPontiac attempted to counter British control over theGreat Lakes region.[160][161][162] A group of Native American warriorslaid siege to British-heldFort Pitt on June 22.[163] In response,Henry Bouquet, the commander of the fort, ordered his subordinate Simeon Ecuyer to give smallpox-infested blankets from the infirmary to aDelaware delegation outside the fort. Bouquet had discussed this with his superior,Sir Jeffrey Amherst, who wrote to Bouquet stating: "Could it not be contrived to send the small pox among the disaffected tribes of Indians? We must on this occasion use every stratagem in our power to reduce them." Bouquet agreed with the proposal, writing back that "I will try to inocculate [sic] the Indians by means of Blankets that may fall in their hands".[164] On 24 June 1763, William Trent, a local trader and commander of the Fort Pitt militia, wrote, "Out of our regard for them, we gave them two Blankets and an Handkerchief out of the Small Pox Hospital. I hope it will have the desired effect."[165][160] The effectiveness of this effort to broadcast the disease is unknown. There are also accounts that smallpox was used as a weapon during theAmerican Revolutionary War (1775–1783).[166][167]
According to a theory put forward inJournal of Australian Studies (JAS) by independent researcher Christopher Warren,Royal Marines used smallpox in 1789 against indigenous tribes inNew South Wales.[168] This theory was also considered earlier inBulletin of the History of Medicine[169] and by David Day.[170] However it is disputed by some medical academics, including Professor Jack Carmody, who in 2010 claimed that the rapid spread of the outbreak in question was more likely indicative ofchickenpox – a more infectious disease which, at the time, was often confused, even by surgeons, with smallpox, and may have been comparably deadly to Aborigines and other peoples without natural immunity to it.[171] Carmody noted that in the 8-month voyage of theFirst Fleet and the following 14 months there were no reports of smallpox amongst the colonists and that, since smallpox has an incubation period of 10–12 days, it is unlikely it was present in the First Fleet; however, Warren argued in theJAS article that the likely source was bottles of variola virus possessed byFirst Fleet surgeons. Ian and Jennifer Glynn, inThe life and death of smallpox, confirm that bottles of "variolous matter" were carried to Australia for use as a vaccine, but think it unlikely the virus could have survived till 1789.[104] In 2007, Christopher Warren offered evidence that the British smallpox may have been still viable.[172] However, the only non-Aborigine reported to have died in this outbreak was a seaman called Joseph Jeffries, who was recorded as being of "American Indian" origin.[173]
DuringWorld War II, scientists from the United Kingdom, United States, and Japan (Unit 731 of theImperial Japanese Army) were involved in research into producing a biological weapon from smallpox.[178] Plans of large scale production were never carried through as they considered that the weapon would not be very effective due to the wide-scale availability of avaccine.[166]
OnVozrozhdeniya Island in theAral Sea, the strongest recipes of smallpox were tested. Suddenly I was informed that there were mysterious cases of mortalities inAralsk. A research ship of the Aral fleet came to within 15 km of the island (it was forbidden to come any closer than 40 km). The lab technician of this ship took samples of plankton twice a day from the top deck. The smallpox formulation – 400 gr. of which was exploded on the island – "got her" and she became infected. After returning home to Aralsk, she infected several people including children. All of them died. I suspected the reason for this and called the Chief of General Staff of the Ministry of Defense and requested to forbid the stop of theAlma-Ata–Moscow train in Aralsk. As a result, the epidemic around the country was prevented. I calledAndropov, who at that time was Chief of KGB, and informed him of the exclusive recipe of smallpox obtained on Vozrazhdenie Island.[180][181]
Others contend that the first patient may have contracted the disease while visiting Uyaly orKomsomolsk-on-Ustyurt, two cities where the boat docked.[182][183]
Responding to international pressures, in 1991 the Soviet government allowed a joint U.S.–British inspection team to tour four of its main weapons facilities atBiopreparat. The inspectors were met with evasion and denials from the Soviet scientists and were eventually ordered out of the facility.[184] In 1992, Soviet defectorKen Alibek alleged that the Soviet bioweapons program at Zagorsk had produced a large stockpile – as much as twenty tons – of weaponized smallpox (possibly engineered to resist vaccines, Alibek further alleged), along with refrigeratedwarheads to deliver it. Alibek's stories about the former Soviet program's smallpox activities have never been independently verified.
In 1997, the Russian government announced that all of its remaining smallpox samples would be moved to theVector Institute inKoltsovo.[184] With the breakup of the Soviet Union and unemployment of many of the weapons program's scientists, U.S. government officials have expressed concern that smallpox and the expertise to weaponize it may have become available to other governments or terrorist groups who might wish to use virus as means of biological warfare.[185] Specific allegations made against Iraq in this respect proved to be false.[186]
Prominent families throughout the world often had several people infected by and/or perish from the disease. For example, several relatives ofHenry VIII of England survived the disease but were scarred by it. These include his sisterMargaret, his wifeAnne of Cleves, and his two daughters:Mary I in 1527 andElizabeth I in 1562. Elizabeth tried to disguise the pockmarks with heavy makeup.Mary, Queen of Scots, contracted the disease as a child but had no visible scarring.
In Europe, deaths from smallpox often changed dynastic succession.Louis XV of France succeeded his great-grandfatherLouis XIV through a series of deaths of smallpox or measles among those higher in the succession line. He himself died of the disease in 1774.Peter II of Russia died of the disease at 14 years of age. Also, before becoming emperor,Peter III of Russia caught the virus and suffered greatly from it.[citation needed] He was left scarred and disfigured. His wife,Catherine the Great, was spared but fear of the virus clearly had its effects on her. She feared for the safety of her son,Paul, so much that she made sure that large crowds were kept at bay and sought to isolate him. Eventually, she decided to have herself inoculated by aBritish doctor,Thomas Dimsdale. While this was considered a controversial method at the time, she succeeded. Paul was later inoculated as well. Catherine then sought to have inoculations throughout her empire stating: "My objective was, through my example, to save from death the multitude of my subjects who, not knowing the value of this technique, and frightened of it, were left in danger." By 1800, approximately two million inoculations had been administered in the Russian Empire.[189]
U.S. PresidentsGeorge Washington,Andrew Jackson, andAbraham Lincoln all contracted and recovered from the disease. Washington became infected with smallpox on a visit toBarbados in 1751.[190] Jackson developed the illness after being taken prisoner by the British during the American Revolution, and though he recovered, his brother Robert did not.[190] Lincoln contracted the disease during his presidency, possibly from his son Tad, and was quarantined shortly after giving the Gettysburg address in 1863.[190]
The famous theologianJonathan Edwards died of smallpox in 1758 following an inoculation.[191]
Soviet leaderJoseph Stalin fell ill with smallpox at the age of seven. His face was badly scarred by the disease. He later had photographs retouched to make his pockmarks less apparent.[192]
Hungarian poetFerenc Kölcsey, who wrote the Hungarian national anthem, lost his right eye to smallpox.[193]
Tradition and religion
The Hindu goddessShitala was worshipped to prevent or cure smallpox.
In the face of the devastation of smallpox, various smallpox gods and goddesses have been worshipped throughout parts of theOld World, for example in China and India. In China, the smallpox goddess was referred to as T'ou-Shen Niang-Niang (Chinese:痘疹娘娘).[194] Chinese believers actively worked to appease the goddess and pray for her mercy, by such measures as referring to smallpox pustules as "beautiful flowers" as aeuphemism intended to avert offending the goddess, for example (the Chinese word for smallpox is天花, literally "heaven flower").[195] In a related New Year's Eve custom it was prescribed that the children of the house wear ugly masks while sleeping, so as to conceal any beauty and thereby avoid attracting the goddess, who would be passing through sometime that night.[195] If a case of smallpox did occur, shrines would be set up in the homes of the victims, to be worshipped and offered to as the disease ran its course. If the victim recovered, the shrines were removed and carried away in a special paper chair or boat for burning. If the patient did not recover, the shrine was destroyed and cursed, to expel the goddess from the house.[194]
In theYoruba language smallpox is known as ṣọpọná, but it was also written as shakpanna, shopona, ṣhapana, and ṣọpọnọ. The word is a combination of 3 words, the verb ṣán, meaning to cover or plaster (referring to the pustules characteristic of smallpox), kpa or pa, meaning to kill, and enia, meaning human. Roughly translated, it means One who kills a person by covering them with pustules.[196] Among theYorùbá people of West Africa, and also inDahomean religion, Trinidad, andin Brazil, The deitySopona, also known asObaluaye, is the deity of smallpox and other deadly diseases (like leprosy, HIV/AIDS, and fevers). One of the most feared deities of theorisha pantheon, smallpox was seen as a form of punishment from Shopona.[197] Worship of Shopona was highly controlled by his priests, and it was believed that priests could also spread smallpox when angered.[197] However, Shopona was also seen as a healer who could cure the diseases he inflicted, and he was often called upon by his victims to heal them.[198] The British government banned the worship of the god because it was believed his priests were purposely spreading smallpox to their opponents.[198][197]
India's first records of smallpox can be found in a medical book that dates back to before 400 CE. This book describes a disease that sounds exceptionally like smallpox.[199] India, like China and the Yorùbá, created a goddess in response to its exposure to smallpox. The Hindu goddessShitala was both worshipped and feared during her reign. It was believed that this goddess was both evil and kind and had the ability to inflict victims when angered, as well as calm the fevers of the already affected.[200][93] Portraits of the goddess show her holding a broom in her right hand to continue to move the disease and a pot of cool water in the other hand in an attempt to soothe patients.[195] Shrines were created where many Indian natives, both healthy and not, went to worship and attempt to protect themselves from this disease. Some Indian women, in an attempt to ward off Shitala, placed plates of cooling foods and pots of water on the roofs of their homes.[201]
In cultures that did not recognize a smallpox deity, there was often nonetheless a belief insmallpox demons, who were accordingly blamed for the disease. Such beliefs were prominent in Japan, Europe, Africa, and other parts of the world. Nearly all cultures who believed in the demon also believed that it was afraid of the color red. This led to the invention of the so-called red treatment, where patients and their rooms would be decorated in red. The practice spread to Europe in the 12th century and was practiced by (among others)Charles V of France andElizabeth I of England.[3] Afforded scientific credibility through the studies byNiels Ryberg Finsen showing that red light reduced scarring,[3] this belief persisted even until the 1930s.
^abcDonald K. Milton (29 November 2012)."What was the primary mode of smallpox transmission? Implications for biodefense".Front Cell Infect Microbiol.2 (150): 150.doi:10.3389/fcimb.2012.00150.PMC3509329.PMID23226686.the rarity of smallpox transmission via fomites suggests that mucosal exposure was not the primary means of transmission and is consistent with a preference for infection via the lower respiratory tract. The rarity of transmission on crowded buses and trains could be evidence that airborne transmission was not important. However, Fenner et al. (1988) state that transmission on public transport was rare because patients seldom traveled after becoming ill.
^Henderson DA (December 2011). "The eradication of smallpox – an overview of the past, present, and future".Vaccine.29 (Suppl 4): D7–9.doi:10.1016/j.vaccine.2011.06.080.PMID22188929.
^Fenner, Frank, Henderson, Donald A, Arita, Isao, Jezek, Zdenek, Ladnyi, Ivan Danilovich. et al. (1988). Smallpox and its eradication / F. Fenner ... [et al.]. World Health Organization.https://apps.who.int/iris/handle/10665/39485Archived 26 May 2020 at theWayback Machine
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^abcRao AR (1972).Smallpox (1st ed.). Bombay: Kothari Book Depot.OCLC723806.
^abHogan CJ, Harchelroad F (22 August 2018)."CBRNE – Smallpox".EMedicine.Archived from the original on 17 October 2008. Retrieved23 September 2006.
^abcd"Smallpox Disease and Its Clinical Management"(PDF).From the training course titled "Smallpox: Disease, Prevention, and Intervention" (www.bt.cdc.gov/agent/smallpox/training/overview). Archived fromthe original(PDF) on 10 May 2016. Retrieved26 December 2007.
^abMoss B (2006). "Poxviridae: the viruses and their replication". In Fields BN, Knipe DM, Howley PM, et al. (eds.).Fields Virology. Vol. 2 (5th ed.). Philadelphia, PA: Lippincott-Raven. pp. 2905–46.ISBN978-0-7817-6060-7.
^Damon I (2006). "Poxviruses". In Fields BN, Knipe DM, Howley PM, et al. (eds.).Fields Virology. Vol. 2 (5th ed.). Philadelphia, PA: Lippincott-Raven. pp. 2947–76.ISBN978-0-7817-6060-7.
^Henderson DA, Inglesby TV, Bartlett JG, Ascher MS, Eitzen E, Jahrling PB, Hauer J, Layton M, McDade J, Osterholm MT, O'Toole T, Parker G, Perl T, Russell PK, Tonat K (June 1999). "Smallpox as a biological weapon: medical and public health management. Working Group on Civilian Biodefense".JAMA.281 (22):2127–37.doi:10.1001/jama.281.22.2127.PMID10367824.
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^abVaccine and Serum Evils, by Herbert M. Shelton, p. 5
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^abDishington A (1999) [1792]. Sinclair SJ (ed.)."United Parishes of Mid and South Yell".The Statistical Account of Scotland Drawn up from the Communications of the Ministers of the Different Parishes.2 (50). University of Edinburgh, University of Glasgow: Edinburgh: William Creech:569–71.OCLC1045293275.Archived from the original on 29 August 2021. Retrieved10 October 2019 – via The Statistical Accounts of Scotland online service.
^Habicht M, Varotto E, Galassi F (April 2022). "The Swiss Canton of Thurgau – not the Kingdom of Bavaria—was the first state to introduce compulsory vaccination against smallpox".Public Health.205:e16 –e17.doi:10.1016/j.puhe.2022.01.028.hdl:10447/621085.PMID35305819.
^Silvia Klein, Irene Schöneberg, Gérard Krause (21 October 2012), "Vom Zwang zur Pockenschutzimpfung zum Nationalen Impfplan",Bundesgesundheitsblatt (in German), vol. 55, pp. 1512–23,doi:10.25646/1620{{citation}}: CS1 maint: multiple names: authors list (link)
^Anders Jarlert:Sveriges Kyrkohistoria. Band 6. Stockholm 2001, S. 33–54.
^Durbach N (2005).Bodily Matters: The Anti-Vaccination Movement in England, 1853–1907. Duke University Press.ISBN978-0-8223-3423-1.
^abcOrenstein WA, Plotkin SA (1999).Vaccines(e–book). Philadelphia: W.B. Saunders Co.ISBN978-0-7216-7443-8.Archived from the original on 12 February 2009. Retrieved12 September 2017.
^Rodrigues BA (1975). "Smallpox eradication in the Americas".Bulletin of the Pan American Health Organization.9 (1):53–68.PMID167890.
^Zhdanov V. "Человек и вирусы (Man and viruses)".Наука и человечество (Science And Mankind), 1984 (in Russian). Moscow: Знание (издательство, Москва) (Knowledge):44–55.
^Centers for Disease Control Prevention (CDC) (June 1996)."Smallpox – Stockholm, Sweden, 1963".MMWR. Morbidity and Mortality Weekly Report.45 (25):538–45.PMID9132571.Archived from the original on 21 July 2020. Retrieved12 September 2017.
^Fenner F (2006).Nature, Nurture and Chance: The Lives of Frank and Charles Fenner. Canberra, ACT 0200: Australian National University Press.ISBN978-1-920942-62-5.{{cite book}}: CS1 maint: location (link)
^abJennings F (1988). "Crucible of War".Empire of fortune : crowns, colonies, and tribes in the Seven Years War in America. Replica Books. pp. 541–42.ISBN978-0-7351-0021-3.
^Peckham HH (1947).Pontiac and the Indian Uprising (1st ed.). Princeton University Press. p. 226.
^Grenier J (2008).The First Way of War: American War Making on the Frontier, 1607–1814 (1st ed.). Cambridge University Press. p. 144.ISBN978-0-521-73263-5.
^Nester WR (2000).Haughty Conquerors: Amherst and the Great Indian Uprising of 1763. Greenwood Publishing Group. pp. 114–15.
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Henderson, Donald Ainslie.Smallpox: the death of a disease: the inside story of eradicating a worldwide killer. (Prometheus Books, 2009).
Hopkins, Donald R.The greatest killer: smallpox in history (U of Chicago press, 2002)online, a major scholarly history
Koplow, David A.Smallpox: The Fight to Eradicate a Global Scourge (U of California Press, 2003)
Kotar, S.L. and J.E. Gessler.Smallpox: A History (McFarland, 2013)online anecdotal accounts from letters and editorials in local newspapers.
Pallen M (2018).The Last Days of Smallpox: Tragedy in Birmingham. UK: Amazon KDP.ISBN978-1-9804-5522-6.
Reinhardt BH (2015).The End of a Global Pox: America and the Eradication of Smallpox in the Cold War Era. University of North Carolina Press. pp. xviii, 268.
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