Did You Have Coronavirus Without Knowing It?

Health experts say the virus has likely been in some U.S. communities for weeks and some people have surely had it without realizing

Markham Heid
Elemental
Published in
4 min readMar 20, 2020

--

Image: BSIP/Getty Images

Follow Elemental’s ongoing coverage of the coronavirus outbreak here.

AsAs health officials issue reports on positive test results and increasingly full ICUs, the gravity of the Covid-19 crisis is setting in. Many of these reports give the impression that the virus only recently began infecting Americans in significant numbers. But health experts say the virus has likely been in some U.S. communities for weeks, and that some people have surely had it without realizing it.

“Yes, it’s possible you may have had it and didn’t know it,” says Dr. Lee Riley, MD, chair of the division of infectious disease and vaccinology at the University of California, Berkeley, School of Public Health. The more recently you were sick, he says, the greater the odds that it could have been Covid-19. But those odds are low.

Riley explains that testing for Covid-19 did not begin in earnest until recently — just this past week, for many U.S. states and cities. “It still takes a few days for the test results to come back, and the results are usually not reported until a certain number of tests have been done,” he says. In other words, there’s a lag between the figures we are seeing and the reality of the virus’s spread. Depending on the area of the country a person lives in, it’s likely that some small percentage of the population had Covid-19 several weeks ago — or, in the case of places like Seattle, even a month ago or longer — and didn’t know it.

While timelines concerning the virus’s spread vary from one place to the next, Riley says a good rule of thumb is that, once your city or town has a confirmed Covid-19 death, the virus has probably been in your community for about two weeks. He also says that, based on virus data collected in China, it’s likely that many people who contract the virus have mild symptoms or, in some cases, no symptoms at all.

“In fact, symptoms for most people are quite mild,” says Dr. Sandro Galea, MD, a physician and dean of Boston University School of Public Health. He says that up to 80% of people who…

--

--

Markham Heid
Elemental

I’m a frequent contributor at TIME, the New York Times, and other media orgs. I write mostly about health and science. I like long walks and the Grateful Dead.