SARS CoV-2 Is (Probably) Becoming Endemic. What Does That Mean?

‘An infection that starts out as an epidemic or pandemic will eventually do one of two things’

Image: Pool/Getty Images

Last February, President Trump famously announced that the coronavirus was going to disappear. “One day — it’s like a miracle — it will disappear.” Now, nearly eight months after that pronouncement, we are facing surging infection rates across the country, with cases rising nationally from 35,000 a day last September to more than 250,000 a day in January. It is time to face facts: This disease isn’t going anywhere. But the good news is that vaccinations are underway and we have been here before with infectious disease.

As the pandemic trudges on, in some regions, the SARS-CoV-2 virus may already be endemic, which is defined as a disease or condition “regularly found among particular people or in a certain area.” An epidemic occurs when a disease spreads through one population. A pandemic is marked by spread through all populations. In both cases, the disease comes from a brand new infectious agent. The human immune system hasn’t seen it before, so we can’t know what it will do. An endemic infection, on the other hand, is when the same infection that persists in a group or population no longer wreaks the same havoc as it did when it was new.

An example of an endemic disease in the United States is chicken pox. Many sexually transmitted diseases, such as syphilis, are endemic worldwide. Other diseases, such as malaria, have been around in certain populations for so long that people in those communities developed a mutation (such as sickle cell trait, which is when someone has only one faulty sickle cell gene instead of two so they don’t develop sickle cell disease) that protects them from dying from it. In Africa, where 85% of sickle cell disease occurs, 22% of highly affected areas have sickle cell trait and over 50% of those people are also infected with malaria. We haven’t eradicated these diseases; we have learned to live with them.

That initial [flu] strain from 1918 is still around. We just don’t get as sick from it anymore.

So, how does a pandemic or epidemic evolve? First, the disease has to be transmitted from person to person. Second, it can’t be a completely deadly infection. Some people have to catch it, infect other people, and recover. If everyone who catches the disease dies, the disease will die off, too. Third, each infected person has to transmit the disease to at least one other person, but not to a large number of people. This rate of transmission only happens after a population has some degree of immunity, meaning some percentage of immune systems have seen it and fought it off. If a population has no immunity, the virus runs rampant and can become an epidemic. An infection that starts out as an epidemic or pandemic will eventually do one of two things: it will either die out (sometimes after resurging in a cyclical way), or it will get to a really low level of transmission and stay there. In other words, it will become endemic.

If you look into the history of endemic diseases, you will see they weren’t always the low-level annoyances they are today. The initial paths they took were usually quite deadly. The strain of influenza that caused the 1918 pandemic is an excellent example. It infected 500 million people and killed as many as 50 million people worldwide. It is considered the most deadly pandemic of all time. It lasted nearly two years and didn’t come to an end until the summer of 1919. But the 1918 flu pandemic didn’t end because of a vaccine — which wasn’t developed until 1942. It ended because those who were infected either died or developed immunity. Influenza never went away. It is airborne and mutates frequently, which is why we have a new version of it — and thus a new vaccine for it — every year. But that initial strain from 1918 is still around. We just don’t get as sick from it anymore.

We are starting to see signs of this happening with the SARS-CoV-2 virus. Like influenza, it is airborne and spreads through person-to-person contact. But in specific places where the virus has already peaked, we are seeing a lower incidence. North Dakota, my home state, had surging rates in mid November that are now tapering. Conversely, California, which had a minor peak in July, is now experiencing soaring rates. This trend repeats itself in state after state. While the positive testing rates from the NYS Health website show a similar upward trend in positive cases, the hospitalizations and deaths fell in June and have remained relatively low.

As an ear, nose and throat (ENT) physician in New York City, I have seen these results firsthand. I have been heading Covid-19 Compliance for major TV productions and worked on one of the first to restart. During shooting in September, we tested over 180 people three times a week and another 200 either once a week or once every other week. After nearly three months, the only person who tested positive was someone who had driven to New York from a state that hadn’t yet experienced an infectious peak.

At some point, this pandemic will either die out or shift to an endemic infection.

Yes, we are seeing a rise in Covid-19 infections. But we are seeing that happen mostly in places that haven’t already had a peak. SARS-CoV-2 has been in New York City since last January, and it struck the city hard and early. While it’s still too early to say what will happen in the year ahead, even though positive testing rates are soaring, statistical signs point to downward trends in hospitalizations and deaths in spots that have already been hit.

Even though our rates of infection in New York City aren’t what they were last spring, SARS-CoV-2 hasn’t gone away. Since this virus is airborne, we have to consider that not only people, but places, can also be infected with the virus. Though considerable social distancing and mask wearing measures are widely in place, we are still breathing in the virus if we are in enclosed spaces and places that have a lot of it.

While we wait for the vaccine to reach everyone, perhaps this virus is already becoming endemic in some places. In New York City, it’s been nearly eleven months since we had our first infection. Is that long enough to stop calling it “novel”? At some point, this pandemic will either die out or shift to an endemic infection. Even though everyone wants it to go away (in the miraculous way Trump predicted), it seems the latter is already happening.

Otolaryngologist. Author of Tooth and Nail:The Making of a Female Fight Doctor & Suck It: Empowered Guide to Breastfeeding, http://dolcenter.net @drlindadahl

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