What to know about “epidemic,” “endemic,” and COVID

Public health officials keep referring to the potential for COVID to become “endemic.” Yet I’m not sure the public actually understands what that means. Let the Word Nerd break it down for you.

Defining important public health terms

According to Merriam-Webster, an epidemic (noun) is an outbreak of disease that affects many people at once. As an adjective, epidemic describes disease that affects an unexpectedly large part of a specific population. That’s the key – it is specific to a community or region. (The prefix epi– comes from Greek to mean “on, at, or besides.” -Demic comes from the Greek “demos” meaning district, country, people.”) For example, when COVID first appeared in Wuhan, China and was only there, it was an epidemic. Epidemic also describes something that is actively spreading.

An outbreak is a sudden rise in disease that typically stays within a certain area or population of people.

An outbreak or epidemic becomes a pandemic when disease spreads over a wide geographical area (many continents and countries) and affects a significant portion of the population. Once COVID started spreading to multiple countries and making thousands of people sick, it became a pandemic. (The prefix pan comes from the Greek pan meaning “all, every.”)

Endemic comes from the Greek inos (meaning “of or belonging to”) + demos (district, people). As an adjective, it describes something belonging to a people or country or prevalent in a field or environment. As a noun, it means an organism restricted to a specific region.

If COVID changes to an endemic virus, the number of infections will remain constant from year to year, and it will be always present, like how malaria is endemic in some parts of Africa. So, if COVID becomes an endemic disease, that means it will become a regular part of our world. What does that look like for us?

Life with endemic COVID

Experts are creating models to predict how COVID might behave in the future. They are looking at current data about COVID as well as reviewing how viruses like the 1918 Spanish Influenza have affected populations in the past. Unfortunately, there are a lot of unknown variables about COVID that make predictions difficult.

Scientists expect there will be better immunity to COVID as more people get vaccinated or are exposed to the virus. The population most likely to experience serious COVID illness could change over time from the elderly to infants and young children. That young population will be vulnerable since it is always getting new members (e.g. babies) with no previous exposure to COVID and no immunity to it.

For adults, duration of immunity will depend on how well our immune systems remember the virus and how much the virus changes with time and transmission. The effect of COVID will be determined by how quickly the population develops immunity (faster is better) and if we can minimize person to person transmission.

Let’s look at measles as an example of a disease that has been successfully eliminated in most of the world. Scientists developed a highly effective vaccine to fight the virus, most of the world has taken that vaccine, and the virus has not evolved. However, measles is endemic in some places where vaccination rates are low, like Africa. Outbreaks of measles do occur if enough unvaccinated people get sick with it and spread it.

What we can do

Some scientists believe COVID could follow the same path as the Spanish flu. It will change into an endemic illness – always around with seasonal, and potentially lethal, outbreaks in the winter. But a lot depends on how quickly and effectively we develop immunity to COVID in our population. So that means a lot depends on us.

Diseases like measles and polio have largely been eliminated because of effective and widespread vaccination. We have vaccines available to eliminate the threat of COVID for the long term. We have the power to determine if COVID will become endemic problem with the potential for serious outbreaks or a disease we don’t have to think about much any more. Wouldn’t it be nice to stop thinking and talking about COVID? There’s a way to make that happen.