A term that we are starting to see used in reference to COVID-19 in countries like Portugal is the term endemic. A basic definition from the Mayo Clinic suggests at first glance that the difference between pandemic and endemic is the geographic location of outbreaks of the disease. Dr. Pritish Tosh, an infectious disease specialist at the Clinic, explains, “In epidemiologic terms, an outbreak refers to a number of cases that exceeds what would be expected. A pandemic is when there is an outbreak that affects most of the world.” The World Health Organization declared COVID-19 a pandemic on March 11, 2020. Since then, the term has become integrated into the public lexicon.
However, Tosh explains, “We use the term endemic when there is an infection within a geographic area that is existing perpetually.” Unfortunately, there is the prospect that COVID could become endemic in most of the world. A closer look at what Tosh means by the words existing perpetually reveals what the future may hold.
According to the Centers for Disease Control and Prevention (the CDC), “The amount of a particular disease that is usually present in a community is referred to as the baseline or endemic level of the disease. This level is not necessarily the desired level, which may in fact be zero, but rather is the observed level. In the absence of intervention and assuming that the level is not high enough to deplete the pool of susceptible persons, the disease may continue to occur at this level indefinitely. Thus, the baseline level is often regarded as the expected level of the disease.” This definition suggests a level of consistency of infection in a particular area, instead of the spikes in cases involved in an outbreak.
Yonatan Grad, Harvard’s Melvin J. and Geraldine L. Glimcher Associate Professor of Immunology and Infectious Diseases, reports, “The expectation that COVID-19 will become endemic essentially means that the pandemic will not end with the virus disappearing; instead, the optimistic view is that enough people will gain immune protection from vaccination and from natural infection such that there will be less transmission and much less COVID-19-related hospitalization and death, even as the virus continues to circulate.” Grad adds that with both the first round of SARS in 2003 and with Ebola in 2014, public health measures stopped the spread and brought the outbreaks to an end.
It can be discouraging to think about a level of COVID that is expected. Remember the CDC’s caveats: “In the absence of intervention and assuming that the level is not high enough to deplete the pool of susceptible persons, the disease may continue to occur at this level indefinitely.” Also remember Grad’s report: “the optimistic view is that enough people will gain immune protection from vaccination and from natural infection such that there will be less transmission and much less COVID-19-related hospitalization and death, even as the virus continues to circulate.” We have lived with this reality with the flu for quite some time. Many Americans accept that receiving flu shot each fall is the best protection against the flu, which still kills thousands every year. The flu vaccines do not provide guaranteed protection against the flu because there are different variants of the flu, as there are with COVID. The flu vaccine is formulated annually based on scientists’ best guess as to what variants will be widespread in the coming year.
Regardless, both the CDC’s and Grad’s statements remind us that we have some control over how the baseline or endemic level ends up being defined. Communities have the means to intervene through increased vaccination rates, which will affect the extent to which the disease continues to circulate. Historically, Americans have seldom been vocal or argumentative about whether or not they choose to be vaccinated against the flu. Nevertheless, government mandates and peer pressure have made vaccination against COVID a heated political issue. To an extent that many of us never expected, the resistance to a life-saving vaccine is helping to ensure that COVID will exist perpetually.
Image Credit: Health checks in India by Gwydion M. Williams is licensed under CC by 2.0.
