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Coronavirus FAQ: What does endemic mean — and are we there yet?

Each week, we answer frequently asked questions about life during the coronavirus crisis. If you have a question you'd like us to consider for a future post, email us at goatsandsoda@npr.org with the subject line: "Weekly Coronavirus Questions." See an archive of our FAQs here.

We all know what the word pandemic means now, but remind me what endemic means again — and are we there yet?

It's been two years since the World Health Organization, on March 11, 2020, officially declared a global pandemic.

Since then, we're all become too familiar with the word pandemic — and sister terms such as epidemic and outbreak.

(If you're fuzzy on the definitions, check out this glossary.)

"But now we're starting to hear the word 'endemic,' " says epidemiology professor Charlotte Baker at Virginia Tech — in reference to a new stage for SARS-CoV-2.

So should we be looking forward to that?

First, let's explain the term.

The word "endemic" comes from the Greek word endēmos, which means "in the population."

In epidemiology, it means that the disease is always present at a baseline level. So it's not down to zero. There are observable cases. But unlike a pandemic or epidemic, in which a disease's behavior is often surprising or unexpected, an illness that has become endemic has become more predictable.

A candy analogy might help.

If you think of a disease as a regular-size KitKat bar, Baker says, and you open the package one day and there are six pieces instead of four, that candy bar is acting more like an epidemic (that is, a sudden spike of a disease that could lead to a pandemic if it spreads globally).

"An epidemic means more cases than we expect," she explains. And if you unwrapped a KitKat bar to reveal six pieces, you'd know something was wrong — "it throws you off, you know something's happening," she says, just as you know that you can't count on things staying the same when there's an epidemic.

As much as none of us want to be joined at the hip with COVID-19 forever — that's the nature of an endemic situation — this stage does have some advantages.

First of all, you know what you're getting: "Endemic means that the disease or infection reached a steady state where it doesn't cause large outbreaks but it still circulates, causing individual cases," explains epidemiologist Dr. Isaac Weisfuse, an adjunct professor in Cornell University's master's of public health program. "There's always a "background rate of infection causing cases — or maybe more cases in enclaves of people who haven't been vaccinated," he adds.

Most strains of influenza are endemic, for example, and you can roughly predict when flu season will begin and end. (Every once in awhile, there are new variants that throw things off, like H1N1 in 2009, which caused a pandemic.) Other endemic diseases in the U.S. include pneumonia and chickenpox. With minimal precautions, such as vaccination, boosters and optional masking, life for most people proceeds as normal.

So are we there yet, endemically speaking?

"We're all in a rush to get to the endemic stage — I would love it," Baker says. "But when it will happen is a really good question."

There are a few potential roadblocks in the way — namely, variants.

"The problem hanging over all of us is what happens if a new variant should occur," Weisfuse says.

In other words, we're far from being able to predict what will happen next with COVID-19. If the disease were a candy bar, we still don't know what to expect when we unwrap it.

Also, Baker notes, the pandemic won't officially be over until the World Health Organization says it's over.

Once that's decided at a special meeting, some countries could still be stuck in epidemic status while others may skip right into endemic.

And, our experts noted, an endemic disease doesn't change the fact that people still need to protect themselves by getting vaccinated.

"The virus might find you if you're unvaccinated or if you have underlying risk factors," Weisfuse says. A small number of those people will still need to be hospitalized, he notes.

I've also heard the terms eliminated and eradicated. Is it too optimistic to hope for that?

Unfortunately, yes.

If a disease is "eliminated" from a country, that means no more transmission among its population (although cases might still be introduced from outsiders). That's the categorization for measles, for example, in the U.S. and a number of European countries.

Other diseases such as smallpox have been eradicated, which means there is zero transmission. (The last naturally occurring case of smallpox was in 1977.)

In both cases, vaccines were to thank for the decline of the diseases.

COVID-19, however, is unlikely to ever be eradicated and doesn't appear to be on track to be eliminated, either, since the virus has been found in animals such as mink, hamsters and deer.

"Once you have a disease with an animal reservoir, it's very hard to eradicate," Weisfuse says. That's because once it's in animals, it can find its way back to humans — like the three people in Hong Kong who reportedly caught COVID-19 from pet-store hamsters.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases," echoed that sentiment in January, when he pointed out that COVID-19 is not on a path to eradication.

"If you look at the history of infectious diseases, we've only eradicated one infectious disease in man, and that's smallpox. That's not going to happen with this virus. But hopefully it will be at such a low level that it doesn't disrupt our normal social, economic and other interactions," he said at the World Economic Forum's Davos Agenda.

And some places are already planning for the endemic stage: Spanish Prime Minister Pedro Sanchez has asked European officials to discuss when COVID-19 should be considered endemic, and California has adopted the first endemic policy for COVID in the U.S. According to The Associated Press, the California plan "emphasizes prevention and quick reaction to outbreaks over mandated masking and business shutdowns."

But it's also important to remember that endemic is not synonymous with harmless. Malaria, for example, is considered endemic in a number of countries. In 2020, the World Health Organization tallied 627,000 deaths from this mosquito-borne disease.

Sheila Mulrooney Eldred is a freelance health journalist in Minneapolis. She has written about COVID-19 for many publications, including The New York Times, Kaiser Health News, Medscape and The Washington Post. More at sheilaeldred.pressfolios.com. On Twitter: @milepostmedia.

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