| Part ofa series on the |
| COVID-19 pandemic |
|---|
 |
|
Medical response |
|
.svg) COVID-19 portal |
COVID-19 has been predicted to become anendemic disease by many experts. The observed behavior ofSARS-CoV-2, the virus that causes COVID-19, suggests it is unlikely it will die out, and the lack of aCOVID-19 vaccine that provides long-lasting immunity against infection means it cannot immediately beeradicated;[1] thus, transition to an endemic phase appears probable. In an endemic phase, people continue to become infected and ill, but in relatively stable numbers.[1] Such a transition may take years or decades.[2] Precisely what would constitute an endemic phase is contested.[3]
Endemic is a frequently misunderstood and misused word outside the realm ofepidemiology.Endemic does not meanmild, or that COVID-19 must become a less hazardous disease. The severity of endemic disease would be dependent on various factors, including the evolution of the virus, population immunity, and vaccine development and rollout.[2][4][5]
COVID-19 endemicity is distinct from the COVID-19public health emergency of international concern, which was ended by theWorld Health Organization on 5 May 2023.[6] Some politicians and commentators have conflated what they termedendemic COVID-19 with the lifting ofpublic health restrictions or a comforting return to pre-pandemic normality.
As of 2024, experts were in disagreement as to whether COVID-19 had yet become endemic.[7][8][9] The transition point of a pandemic into an endemic state is not well-defined, and whether this has occurred differs according to the definitions used.[10]
Aninfectious disease is said to beendemic when the number of infections is predictable.[11] This includes diseases withinfection rates that are predictably high (calledhyperendemic), as well as diseases with infection rates that are predictably low (calledhypoendemic).[11]Endemic does not meanmild: a disease with a stable infection rate can be associated with any level of disease severity and anymortality rate among infected people.[12] Endemic COVID-19 is not a synonym for COVID-19 infection becoming safe, or formortality andmorbidity becoming less of a problem. Theprevalence and resultingdisease burden is dependent on factors such as how quickly newvariants emerge, the uptake ofCOVID-19 vaccines, and changes todisease virulence (a factor that depends on both the virus's own characteristics and people's immunity against it), rather than being dependent on endemicity.[2]
Generally speaking, all newemerging infectious diseases have five potential outcomes:[5]
Additionally, if an infectious disease becomes endemic, there is no guarantee that the disease will remain endemic forever. A disease that is usually endemic can becomeepidemic or pandemic in the future.[5] For example, in some years,influenza becomes a pandemic, even though it is not usually a pandemic.
During the course of the COVID-19 pandemic, it became apparent that the SARS-CoV-2 virus was unlikely to die out.[1] Eradication is widely believed to be impossible, especially in the absence of a vaccine that provides long-lasting immunity against infection from COVID-19.[1]
While all of the other outcomes are possible – sporadic, epidemic, pandemic, or endemic – many experts believe that COVID-19 is most likely to become endemic.[1][5] Endemicity is characterized by continued infections by the virus, but with a more stable, predictable number of infected people than in the other three categories.
There is no single agreed definition or metric that proves that COVID-19 has become endemic.[14]
A March 2022review said that it was "inevitable" theSARS-CoV-2 virus would become endemic to humans, and that it was essential to develop public health strategies to anticipate this.[4] A June 2022 review predicted that the virus that causes COVID-19 would become the fifth endemic seasonal coronavirus, alongside four otherhuman coronaviruses.[5] A February 2023 review of the fourcommon cold coronaviruses concluded that the virus would become seasonal and, like the common cold, cause less severe disease for most people.[15]
As of 2023[update] it was thought a transition to endemic COVID-19 could take years or decades.[2]
The largest determinant of how endemicity manifests is the level ofimmunity people have acquired, either as a result ofvaccination or of direct infection.[1] The severity of a disease in an endemic phase depends on how long-lasting immunity against severe outcomes is. If such immunity is lifelong, or lasts longer than immunity against re-infection, then re-infections will mostly be mild, resulting in an endemic phase with mild disease severity.[1] In other existinghuman coronaviruses, protection against infection is temporary, but observed reinfections are relatively mild.[1]
Status as an endemic disease requires a stable level of transmission. Anything that could affect the level of transmission could determine whether the disease becomes and remains endemic, or takes another path. These factors include but are not limited to:[13]
Many of the factors that determine whether COVID-19 becomes endemic are not unique to COVID-19.[13]
On 5 May 2023, the WHO declared that the pandemic was no longer apublic health emergency of international concern. The WHO's Director-General, Dr.Tedros Adhanom Ghebreyesus, stated that the pandemic's downward trend over the preceding year "has allowed most countries to return to life as we knew it before COVID-19", though cautioning that new variants could still pose a threat and that the conclusion of the current state of emergency did not mean that the COVID-19 is no longer a worldwide health concern.[16][17][18]
According to historian Jacob Steere-Williams, whatendemicity means has evolved since the 19th century, and the desire to label COVID-19 as being endemic in early 2022 was a political and cultural phenomenon connected to a desire to see the pandemic as being over.[3]
Paleovirologist Aris Katzourakis wrote in January 2022 that the wordendemic was one of the most misused of theCOVID-19 pandemic.[19] A 2023editorial on endemicity in theInternational Nursing Review journal said that "Traps for unwary politicians and commentators include statements on scientific matters that fall well outside their knowledge and experience, and the danger of adopting and misusing esoteric terminology that has nuanced meanings within professional circles."[20]
When COVID-19 emerged, most people were unfamiliar with the termendemic.[21] Although the representations of endemic COVID-19 in English-language media reports were decidedly negative during the early weeks of the pandemic, since then, the concept of endemicity has been represented in the media as a positive outcome.[21] English-language media coverage, usingendemic more like abuzzword to change the public's view of COVID-19 than according to a strict scientific definition,anchored the concept of endemic COVID-19 toseasonal influenza.[21] By December 2021, endemicity was being represented in media as an opportunity that people should seize to "live with the virus" and achieve a "new normal".[21] People were being told that endemicity was a desirable outcome that would achieve not only actualendemicity (a stable, predictable number of infections), but that would also bring them familiar seasonal patterns of infection, manageable demands on healthcare, and a lessvirulent, relatively harmless disease.[21]
Media coverage has alsoobjectified endemicity through themetaphor of ajourney, especially as the destination at the end of "the path to normality".[21]
In the absence of eradication, the virus will likely become endemic, a process that could take years to decades. We will be able to establish that endemic persistence has been reached if the virus shows repeatable patterns in prevalence year on year, for example, regular seasonal fluctuations and no out-of-season peaks. The form this endemic persistence will take remains to be determined, and the eventual infection prevalence and disease burden will depend on the rate of emergence of antigenically distinct lineages, our ability to roll out and update vaccines, and the future trajectory of virulence (Fig. 4c)....Meanwhile, focusing on the epidemiology of the pathogen, it is important to bear in mind that the transition from a pandemic to future endemic existence of SARS-CoV-2 is likely to be long and erratic, rather than a short and distinct switch, and that endemic SARS-CoV-2 is by far not a synonym for safe infections, mild COVID-19 or a low population mortality and morbidity burden.
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.