Apandemic (/pænˈdɛmɪk/pan-DEM-ik) is anepidemic of aninfectious disease that has a sudden increase in cases and spreads across a large region, for instance multiplecontinents or worldwide, affecting a substantial number of individuals. Widespreadendemic diseases with a stable number of infected individuals such as recurrences ofseasonal influenza are generally excluded as they occur simultaneously in large regions of the globe rather than being spread worldwide.
A medical dictionary definition of pandemic is "anepidemic occurring on a scale that crosses international boundaries, usually affecting people on a worldwide scale".[14] A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance,cancer is responsible for many deaths but is not considered a pandemic because the disease is notcontagious—i.e. easily transmissible—and not even simplyinfectious.[15] This definition differs from colloquial usage in that it encompasses outbreaks of relatively mild diseases.[16][17]
TheWorld Health Organization (WHO) has a category ofPublic Health Emergency of International Concern, defined as "an extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease and to potentially require a coordinated international response".[18] There is a rigorous process underlying this categorization and a clearly defined trajectory of responses.[19]
A WHO-sponsored international body, tasked with preparing aninternational agreement on pandemic prevention, preparedness and response has defined a pandemic as "the global spread of a pathogen or variant that infects human populations with limited or no immunity through sustained and high transmissibility from person to person, overwhelming health systems with severe morbidity and high mortality, and causing social and economic disruptions, all of which require effective national and global collaboration and coordination for its control".[20]
The word comes from theGreekπαν-pan- meaning'all, every', andδῆμοςdemos'people'.
A common early characteristic of a pandemic is a rapid, sometimesexponential, growth in the number of infections, coupled with a widening geographical spread.[21]
WHO utilises different criteria to declare aPublic Health Emergency of International Concern (PHEIC), its nearest equivalent to the termpandemic.[22] The potential consequences of an incident are considered, rather than its current status.[23] For example,polio wasdeclared a PHEIC in 2014 even though only 482 cases were reported globally in the previous year;[24] this was justified by concerns that polio might break out of its endemic areas and again become a significant health threat globally.[25] The PHEIC status of polio is reviewed regularly and is ongoing, despite the small number of cases annually.[b][26]
The end of a pandemic is more difficult to delineate. Generally, past epidemics and pandemics have faded out as the diseases become accepted into people's daily lives and routines, becomingendemic.[27] The transition from pandemic to endemic may be defined based on:
a high proportion of the global population having immunity (through either natural infection or vaccination)
An endemic disease is always present in a population, but at a relatively low and predictable level. There may be periodic spikes of infections or seasonality, (e.g.influenza) but generally the burden on health systems is manageable.[28]
Infographic illustrating the benefits of a treaty for pandemic prevention
Pandemicprevention comprises activities such as anticipatory research and development of therapies and vaccines, as well as monitoring for pathogens and disease outbreaks which may have pandemic potential.[30]Routine vaccination programs are a type of prevention strategy, holding back diseases such asinfluenza andpolio which have caused pandemics in the past, and could do so again if not controlled.[31] Prevention overlaps withpreparedness which aims to curtail an outbreak and prevent it getting out of control - it involves strategic planning, data collection and modelling to measure the spread, stockpiling of therapies, vaccines, and medical equipment, as well as public health awareness campaigning.[32] By definition, a pandemic involves many countries so international cooperation, data sharing, and collaboration are essential; as is universal access to tests and therapies.[30]
Collaboration – In response to the COVID-19 pandemic, WHO established a Pandemic Hub in September 2021 in Berlin, aiming to address weaknesses around the world in how countries detect, monitor and manage public health threats. The Hub's initiatives include using artificial intelligence to analyse more than 35,000 data feeds for indications of emerging health threats, as well as improving facilities and coordination between academic institutions and WHO member countries.[33]
Detection – In May 2023, WHO launched the International Pathogen Surveillance Network (IPSN) (hosted by the Pandemic Hub) aiming to detect and respond to disease threats before they become epidemics and pandemics, and to optimize routine disease surveillance. The network provides a platform to connect countries, improving systems for collecting and analysing samples of potentially harmfulpathogens.[34]Wastewater surveillance can for example provide early warnings by detecting pathogens in sewage.[35]
Therapies and vaccines – TheCoalition for Epidemic Preparedness Innovations (CEPI) is developing a program[as of?] to condense new vaccine development timelines to 100 days, a third of the time it took to develop a COVID-19 vaccine. CEPI aims to reduce global epidemic and pandemic risk by developing vaccines against known pathogens as well as enabling rapid response toDisease X.[36][37] In the US, theNational Institute of Allergy and Infectious Diseases (NIAID) has developed a Pandemic Preparedness Plan which focuses on identifying viruses of concern and developing diagnostics and therapies (including prototype vaccines) to combat them.[38][39]
Modeling is important to inform policy decisions. It helps to predict the burden of disease on healthcare facilities, the effectiveness of control measures, projected geographical spread, and timing and extent of future pandemic waves.[40]
Public awareness involves disseminating reliable information, ensuring consistency in message, transparency, and steps to discreditmisinformation.[41]
Stockpiling involves maintaining strategicstockpiles of emergency supplies such aspersonal protective equipment, drugs and vaccines, and equipment such as respirators. Many of these items have limitedshelf life, so they requirestock rotation even though they may be rarely used.[43]
The COVID-19 pandemic highlighted a number of ethical and political issues which must be considered during a pandemic. These included decisions about who should be prioritised for treatment while resources are scarce; whether or not to make vaccination compulsory; the timing and extent of constraints on individual liberty, how to sanction individuals who do not comply with emergency regulations, and the extent of international collaboration and resource sharing.[44][45]
Goals of mitigation include delaying and reducing peak burden on healthcare (flattening the curve) and lessening overall cases and health impact.[46][47] Also, increasing healthcare capacity (raising the line, as by increasing bed count, personnel, and equipment) helps to meet increased demand.[48][49]
Mitigation attempts that are inadequate in strictness or duration—such as premature relaxation of physical distancing rules or stay-at-home orders—can allow a resurgence after the initial surge and mitigation.[50]
Without pandemic containment measures—such as social distancing, vaccination, and use of face masks—pathogens can spread exponentially.[51] This graphic shows how early adoption of containment measures tends to protect wider swaths of the population.
The Red Cross recommended two-layer gauze masks to contain the Spanish flu (1918).[52]
The basic strategies in the control of an outbreak arecontainment andmitigation. Containment may be undertaken in the early stages of the outbreak, includingcontact tracing and isolating infected individuals to stop the disease from spreading to the rest of the population, other public health interventions on infection control, and therapeutic countermeasures such asvaccinations which may be effective if available.[53] When it becomes apparent that it is no longer possible to contain the spread of the disease, management will then move on to the mitigation stage, in which measures are taken to slow the spread of the disease and mitigate its effects on society and the healthcare system. In reality, containment and mitigation measures may be undertaken simultaneously.[54]
A key part of managing an infectious disease outbreak is trying to decrease the epidemic peak, known as "flattening the curve".[46][49] This helps decrease the risk of health services being overwhelmed and provides more time for a vaccine and treatment to be developed.[46][49] A broad group ofnon-pharmaceutical interventions may be taken to manage the outbreak.[49] In a flu pandemic, these actions may include personal preventive measures such as hand hygiene, wearing face-masks, and self-quarantine; community measures aimed atsocial distancing such as closing schools and canceling mass gatherings; community engagement to encourage acceptance and participation in such interventions; and environmental measures such as cleaning of surfaces.[47]
Another strategy,suppression, requires more extreme long-term non-pharmaceutical interventions to reverse the pandemic by reducing thebasic reproduction number to less than1. The suppression strategy, which includes stringent population-wide social distancing, home isolation of cases, and household quarantine, was undertaken byChina during theCOVID-19 pandemic where entire cities were placed under lockdown; such a strategy may carry with it considerable social and economic costs.[55]
For a novelinfluenza virus, WHO previously applied a six-stage classification to delineate the process by which the virus moves from the first few infections in humans through to a pandemic. Starting with phase 1 (infections identified in animals only), it moves through phases of increasing infection and spread to phase 6 (pandemic).[56] In February 2020, a WHO spokesperson clarified that the system is no longer in use.[57]
Influenza intervals in the CDC's Pandemic Intervals Framework
In 2014, the United StatesCenters for Disease Control and Prevention (CDC) introduced a framework for characterising the progress of an influenza pandemic titled thePandemic Intervals Framework.[58] The six intervals of the framework are as follows:
investigation of cases of novel influenza,
recognition of increased potential for ongoing transmission,
initiation of a pandemic wave,
acceleration of a pandemic wave,
deceleration of a pandemic wave, and
preparation for future pandemic waves.
At the same time, the CDC adopted thePandemic Severity Assessment Framework (PSAF) to assess the severity of influenza pandemics.[58] The PSAF rates the severity of an influenza outbreak on two dimensions: clinical severity of illness in infected persons; and the transmissibility of the infection in the population.[59] This tool was not applied during the COVID-19 pandemic.[60]
Total confirmed cases of COVID-19 per million people[61]
SARS-CoV-2, a new strain ofcoronavirus, was first detected in the city ofWuhan, Hubei Province, China, in December 2019.[62] The outbreak was characterized as aPublic Health Emergency of International Concern (PHEIC) between January 2020 and May 2023 by WHO.[63][64] The number of people infected with COVID-19 has reached more than 767 million worldwide, with a death toll of 6.9 million.[c][65] It is considered likely that the virus will eventually become endemic and, like the common cold, cause less severe disease for most people.[66]
A world map illustrating the proportion of population infected with HIV in 2019
HIV/AIDS was first identified as a disease in 1981, and is an ongoing worldwidepublic health issue.[67][68] Since then, HIV/AIDS has killed an estimated 40 million people with a further 630,000 deaths annually; 39 million people are currently living withHIV infection.[d][67] HIV has azoonotic origin, having originated in nonhumanprimates inCentral Africa and transferred to humans in the early 20th century.[69] The most frequent mode of transmission of HIV is through sexual contact with an infected person. There may be a short period of mild, nonspecific symptoms followed by an asymptomatic (but nevertheless infectious) stage calledclinical latency – without treatment, this stage can last between 3 and 20 years. The only way to detect infection is by means of a HIV test.[70] There is no vaccine to prevent HIV infection, but the disease can be held in check by means ofantiretroviral therapy.[71]
Historical accounts of epidemics are often vague or contradictory in describing how victims were affected. A rash accompanied by a fever might be smallpox, measles, scarlet fever, orvaricella, and it is possible that epidemics overlapped, with multiple infections striking the same population at once. It is often impossible to know the exact causes of mortality, althoughancient DNA studies can sometimes detect residues of certain pathogens.[72]
It is assumed that, prior to theNeolithic Revolution around 10,000 BC, disease outbreaks were limited to a single family or clan, and did not spread widely before dying out. The domestication of animals increased human-animal contact, increasing the possibility of zoonotic infections. The advent of agriculture, and trade between settled groups, made it possible for pathogens to spread widely. As the population increased, contact between groups became more frequent. A history of epidemics maintained by the Chinese Empire from 243 B.C. to 1911 A.C. shows an approximate correlation between the frequency of epidemics and the growth of the population.[74]
Here is an incomplete list of known epidemics which have spread widely enough to merit the title "pandemic".
Plague of Athens (430 to 426 BC): During thePeloponnesian War, an epidemic killed a quarter of the Athenian troops and a quarter of the population. This disease fatally weakened the dominance ofAthens, but the sheer virulence of the disease prevented its wider spread; i.e., it killed off its hosts at a rate faster than they could spread it. The exact cause of the plague was unknown for many years. In January 2006, researchers from theUniversity of Athens analyzedteeth recovered from amass grave underneath the city and confirmed the presence ofbacteria responsible fortyphoid fever.[75]
Antonine Plague (165 to 180 AD): Possibly measles or smallpox brought to the Italian peninsula by soldiers returning from the Near East, it killed a quarter of those infected, up to five million in total.[76]
Plague of Cyprian (251–266 AD): A second outbreak of what may have been the same disease as the Antonine Plague killed (it was said) 5,000 people a day inRome.[77]
Plague of Justinian (541 to 549 AD): Also known as theFirst Plague Pandemic. This epidemic started inEgypt and reachedConstantinople the following spring, killing (according to the Byzantine chroniclerProcopius) 10,000 a day at its height, and perhaps 40% of the city's inhabitants. The plague went on to eliminate a quarter to half thehuman population of the known world and was identified in 2013 as being caused bybubonic plague.[78][79]
Black Death (1331 to 1353): Also known as theSecond Plague Pandemic. The total number of deaths worldwide is estimated at 75 to 200 million. Starting in Asia, the disease reached the Mediterranean and western Europe in 1348 (possibly from Italian merchants fleeing fighting inCrimea) and killed an estimated 20 to 30 million Europeans in six years;[80] a third of the total population,[81] and up to a half in the worst-affected urban areas.[82] It was the first of a cycle of Europeanplague epidemics that continued until the 18th century;[83] there were more than 100 plague epidemics in Europe during this period,[84] including theGreat Plague of London of 1665–66 which killed approximately 100,000 people, 20% of London's population.[85]
1817–1824 cholera pandemic. Previously endemic in theIndian subcontinent, the pandemic began inBengal, then spread across India by 1820. The deaths of 10,000 British troops were documented - it is assumed that tens of thousands of Indians must have died.[86] The disease spread as far as China,Indonesia (where more than 100,000 people succumbed on the island ofJava alone)[87] and theCaspian Sea before receding. Subsequent cholera pandemics during the 19th century are estimated to have caused many millions of deaths globally.[88][89]Great Plague of Marseille in 1720 killed a total of 100,000 people
Third plague pandemic (1855–1960): Starting in China, it is estimated to have caused over 12 million deaths in total, the majority of them in India.[90][91] During this pandemic, the United States saw its first outbreak: theSan Francisco plague of 1900–1904.[92] The causative bacterium,Yersinia pestis, was identified in 1894.[93] The association with fleas, and in particular rat fleas in urban environments, led to effective control measures. The pandemic was considered to be over in 1959 when annual deaths due to plague dropped below 200. The disease is nevertheless present in the rat population worldwide and isolated human cases still occur.[94]
The 1918–1920Spanish flu infected half a billion people[95] around the world, including on remotePacific islands and in theArctic—killing 20 to 100 million.[95][96] Most influenza outbreaks disproportionately kill the very young and the very old, but the 1918 pandemic had an unusually high mortality rate for young adults.[97] It killed more people in 25 weeks than AIDS did in its first 25 years.[98][99] Mass troop movements and close quarters during World WarI caused it to spread andmutate faster, and the susceptibility of soldiers to the flu may have been increased by stress,malnourishment andchemical attacks.[100] Improved transportation systems made it easier for soldiers, sailors and civilian travelers to spread the disease.[101]
Beginning from the Middle Ages, encounters between European settlers and native populations in the rest of the world often introduced epidemics of extraordinary virulence. Settlers introduced novel diseases which were endemic in Europe, such assmallpox,measles,pertussis andinfluenza, to which theindigenous peoples had no immunity.[102][103] The Europeans infected with such diseases typically carried them in adormant state, were actively infected butasymptomatic, or had only mild symptoms.[104]
Smallpox was the most destructive disease that was brought by Europeans to the Native Americans, both in terms ofmorbidity and mortality. The first well-documented smallpox epidemic in the Americas began inHispaniola in late 1518 and soon spread to Mexico.[104] Estimates of mortality range from one-quarter to one-half of the population of central Mexico.[105] It is estimated that over the 100 years after European arrival in 1492, the indigenous population of the Americas dropped from 60 million to only 6 million, due to a combination of disease, war, and famine. The majority these deaths are attributed to successive waves of introduced diseases such as smallpox, measles, and typhoid fever.[106][107][108]
InAustralia, smallpox was introduced by European settlers in 1789 devastating theAustralian Aboriginal population, killing an estimated 50% of those infected with the disease during the first decades of colonisation.[109] In the early 1800s, measles, smallpox and intertribal warfare killed an estimated 20,000 New ZealandMāori.[110]
In 1848–49, as many as 40,000 out of 150,000Hawaiians are estimated to have died ofmeasles,whooping cough andinfluenza. Measles killed more than 40,000Fijians, approximately one-third of the population, in 1875,[111] and in the early 19th century devastated theGreat Andamanese population.[112] InHokkaido, an epidemic of smallpox introduced by Japanese settlers is estimated to have killed 34% of the nativeAinu population in 1845.[113]
Prevention of future pandemics requires steps to identify future causes of pandemics and to take preventive measures before the disease moves uncontrollably into the human population.
For example, influenza is a rapidly evolving disease which has caused pandemics in the past and has the potential to cause future pandemics. WHO collates the findings of 144 national influenza centres worldwide which monitor emerging flu viruses. Virus variants which are assessed as likely to represent a significant risk are identified and can then be incorporated into the next seasonal influenza vaccine program.[114]
In a press conference on 28 December 2020, Mike Ryan, head of the WHO Emergencies Program, and other officials said the current COVID-19 pandemic was "not necessarily the big one" and "the next pandemic may be more severe." They called for preparation.[115] WHO and the UN have warned the world must tackle the cause of pandemics and not just the health and economic symptoms.[116]
There is always a possibility that a disease which has caused epidemics in the past may return in the future.[74] It is also possible that little known diseases may become more virulent; in order to encourage research, a number of organisations which monitor global health have drawn up lists of diseases which may have pandemic potential; see table below.[e]
List of potential pandemic diseases according to global health organisations
Following the end of the COVID-19 pandemic Public Health Emergency of International Concern deceleration by WHO, WHO Director GeneralTedros Ghebreyesus stated he would not hesitate to re-declare COVID-19 a PHEIC should the global situation worsen in the coming months or years.
Influenza was first described by the Greek physicianHippocrates in 412BC.[126] Since the Middle Ages, influenza pandemics have been recorded every 10 to 30 years as the virus mutates to evade immunity.[127][128]
Influenza is anendemic disease, with a fairly constant number of cases which vary seasonally and can, to a certain extent, be predicted.[129] In a typical year, 5–15% of the population contracts influenza. There are 3–5 million severe cases annually, with up to 650,000 respiratory-related deaths globally each year.[130] The1889–1890 pandemic is estimated to have caused around a million fatalities,[131] and the "Spanish flu" of 1918–1920 eventually infected about one-third of theworld's population and caused an estimated 50million fatalities.[95]
TheGlobal Influenza Surveillance and Response System is a global network of laboratories that has for purpose to monitor the spread ofinfluenza with the aim to provide WHO with influenza control information.[132] More than two million respiratory specimens are tested by GISRS annually to monitor the spread and evolution of influenza viruses through a network of about 150 laboratories in 114 countries representing 91% of the world's population.[133]
Antibiotic-resistant microorganisms, which sometimes are referred to as "superbugs", may contribute to the re-emergence of diseases with pandemic potential that are currently well controlled.[134]
For example, cases of tuberculosis that are resistant to traditionally effective treatments remain a cause of great concern to health professionals. Every year, nearly half a million new cases ofmultidrug-resistant tuberculosis (MDR-TB) are estimated to occur worldwide.[135] China and India have the highest rate of MDR-TB.[136] WHO reports that approximately 50 million people worldwide are infected with MDR-TB, with 79 percent of those cases resistant to three or more antibiotics. Extensively drug-resistant tuberculosis (XDR-TB) was first identified in Africa in 2006 and subsequently discovered to exist in 49 countries. During 2021 there were estimated to be around 25,000 cases XDR-TB worldwide.[137]
There are two groups of infectious diseases that may be affected by climate change. The first group arevector-borne diseases which are transmitted via insects such as mosquitos or ticks.[139] Some of these diseases, such asmalaria,yellow fever, anddengue fever, can have potentially severe health consequences. Climate can affect the distribution of these diseases due to the changing geographic range of their vectors, with the potential to cause serious outbreaks in areas where the disease has not previously been known.[140] The other group compriseswater-borne diseases such as cholera, dysentery, and typhoid which may increase in prevalence due to changes in rainfall patterns.[141]
The October 2020 'era of pandemics' report by theUnited Nations'Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, written by 22 experts in a variety of fields, said the anthropogenic destruction ofbiodiversity is paving the way to the pandemic era and could result in as many as 850,000 viruses being transmitted from animals—in particularbirds andmammals—to humans. The"exponential rise" in consumption and trade of commodities such asmeat,palm oil, and metals, largely facilitated by developed nations, and agrowing human population, are the primary drivers of this destruction. According toPeter Daszak, the chair of the group who produced the report, "there is no great mystery about the cause of the Covid-19 pandemic or any modern pandemic. The same human activities that driveclimate change and biodiversity loss also drive pandemic risk through their impacts on our environment." Proposed policy options from the report include taxing meat production and consumption, cracking down on the illegal wildlife trade, removing high-risk species from the legal wildlife trade, eliminating subsidies to businesses that are harmful to the natural world, and establishing a global surveillance network.[142][143][144]
Permafrost covers a fifth of the northern hemisphere and is made up of soil that has been kept at temperatures below freezing for long periods. Viable samples of viruses have been recovered from thawing permafrost, after having been frozen for many years, sometimes for millennia. There is a remote possibility that a thawed pathogen could infect humans or animals.[146][147]
Experts have raised concerns that advances inartificial intelligence could facilitate the design of particularly dangerous pathogens with pandemic potential. They recommended in 2024 that governments implement mandatory oversight and testing requirements.[148]
In 2016, the commission on a Global Health Risk Framework for the Future estimated that pandemic disease events would cost the global economy over $6 trillion in the 21st century—over $60 billion per year.[149] The same report recommended spending $4.5 billion annually on global prevention and response capabilities to reduce the threat posed by pandemic events, a figure that the World Bank Group raised to $13 billion in a 2019 report.[150] It has been suggested that such costs be paid from a tax on aviation rather than from, e.g., income taxes,[151] given the crucial role of air traffic in transforming local epidemics into pandemics (being the only factor considered in state-of-the-art models of long-range disease transmission[152]).
The COVID-19 pandemic is expected to have a profoundnegative effect on the global economy, potentially for years to come, with substantial drops in GDP accompanied by increases in unemployment noted around the world.[49] The slowdown of economic activity early in the COVID-19 pandemic had a profound effect on emissions of pollutants and greenhouse gases.[153][154][155] Analysis of ice cores taken from the Swiss Alps has revealed a reduction in atmospheric lead pollution over a four-year period corresponding to the years 1349 to 1353 (when the Black Death was ravaging Europe), indicating a reduction in mining and economic activity generally.[156]
^Most medical sources, including the WHO, do not refer to HIV/AIDS as a pandemic; those that do refer to it in the past-tense to separate the acute and chronic phases.
^Ross E (20 October 2022)."What is the difference between a pandemic and a PHEIC (Video explainer)".Chatham House, The Royal Institute of International Affairs. Retrieved25 August 2023.There's a whole infrastructure and official process around designating something a PHEIC and designating that an outbreak is no longer a PHEIC. There's none of that when it comes to calling an outbreak pandemic.
^Savulescu J, Wilkinson D (1 May 2023).Pandemic Ethics. Oxford, UK: Oxford University Press.ISBN9780192871688.
^abcAnderson RM, Heesterbeek H, Klinkenberg D, Hollingsworth TD (March 2020)."How will country-based mitigation measures influence the course of the COVID-19 epidemic?".Lancet.395 (10228):931–934.doi:10.1016/S0140-6736(20)30567-5.PMC7158572.PMID32164834.A key issue for epidemiologists is helping policymakers decide the main objectives of mitigation—e.g., minimizing morbidity and associated mortality, avoiding an epidemic peak that overwhelms health-care services, keeping the effects on the economy within manageable levels, and flattening the epidemic curve to wait for vaccine development and manufacture on the scale and antiviral drug therapies.
^"3. Strategies for Disease Containment".Ethical and Legal Considerations in Mitigating Pandemic Disease: Workshop Summary. National Academies Press (US). 2007.
^"WHO says it no longer uses 'pandemic' category, but virus still emergency". Reuters. 24 February 2020.Archived from the original on 18 March 2020.For the sake of clarification, WHO does not use the old system of 6 phases—that ranged from phase 1 (no reports of animal influenza causing human infections) to phase 6 (a pandemic)—that some people may be familiar with from H1N1 in 2009.
^abHolloway R, Rasmussen SA, Zaza S, Cox NJ, Jernigan DB (September 2014)."Updated preparedness and response framework for influenza pandemics"(PDF).MMWR. Recommendations and Reports.63 (RR-06). Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention:1–18.PMID25254666. Retrieved10 May 2020.
^Harrison CM, Doster JM, Landwehr EH, Kumar NP, White EJ, Beachboard DC, Stobart CC (February 2023)."Evaluating the Virology and Evolution of Seasonal Human Coronaviruses Associated with the Common Cold in the COVID-19 Era".Microorganisms.11 (2): 445.doi:10.3390/microorganisms11020445.PMC9961755.PMID36838410.After evaluating the biology, pathogenesis, and emergence of the human coronaviruses that cause the common cold, we can anticipate that with increased vaccine immunity to SARS-CoV-2, it will become a seasonal, endemic coronavirus that causes less severe disease in most individuals. Much like the common cold CoVs, the potential for severe disease will likely be present in those who lack a protective immune response or are immunocompromised.
^ab"HIV/AIDS Factsheet".World Health Organization. 2 August 2023. Retrieved2 August 2023.
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^Stéphane Barry and Norbert Gualde, inL'Histoire No. 310, June 2006, pp. 45–46, say "between one-third and two-thirds"; Robert Gottfried (1983). "Black Death" inDictionary of the Middle Ages, volume 2, pp. 257–267, says "between 25 and 45 percent".
^abFrancis JM (2005).Iberia and the Americas culture, politics, and history: A Multidisciplinary Encyclopedia. Santa Barbara, California: ABC-CLIO.ISBN1851094210.
^Hays J (2005).Epidemics and Pandemics: Their Impacts on Human History. Bloomsbury Publishing.ISBN9781851096589.
^Dowling P (2021).Fatal contact: How epidemics nearly wiped out Australia's first peoples. Clayton, Victoria: Monash University Publishing. pp. 30–31,60–63.ISBN9781922464460.
^Heymann D, Ross E, Wallace J (23 February 2022)."The next pandemic – when could it be?".Chatham House, The Royal Institute of International Affairs. Retrieved24 July 2023.
^Shally-Jensen M, ed. (2010)."Influenza".Encyclopedia of Contemporary American Social Issues. Vol. 2.ABC-CLIO. p. 1510.ISBN978-0-31339205-4.The Asiatic flu killed roughly one million individuals
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McKenna N (September 2020). "Return of the Germs: For more than a century drugs and vaccines made astounding progress against infectious diseases. Now our best defenses may be social changes".Scientific American.323 (3):50–56.What might prevent or lessen [the] possibility [of a virus emerging and finding a favorable human host] is more prosperity more equally distributed – enough that villagers in South Asia need not trap and sell bats to supplement their incomes and that, low-wage workers in the U.S. need not go to work while ill because they have no sick leave
Quammen D (24 August 202)."Did Pangolin Trafficking Cause the Coronavirus Pandemic".The New Yorker. pp. 26–31 (31).More field research is needed [...]. More sampling of wild animals. More scrutiny of genomes. More cognizance of the fact that animal infections can become human infections because humans are animals. We live in a world of viruses, and we have scarcely begun to understand this one. [COVID-19
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