The big thing I got wrong about COVID-19

John Skylar, PhD
5 min readMar 27, 2020

As an emerging disease researcher, I learned that with new viruses you are never working with good information. The thing about emerging diseases is that you’ve never seen them before. You’re going to make mistakes. So when this thing first started, I was counting on being wrong — either because the early data would be wrong, or my instincts would.

Photo by Anshu A on Unsplash

In mid-January, I was telling my friends to wash their hands because flu was a bigger threat to them than COVID-19. At the time, this was correct. But I thought it would stay correct; I was wrong, and I was wrong for reasons that had nothing to do with the disease.

When SARS-CoV-2, the agent that causes this disease, was spreading in Wuhan, I followed it closely. The rapid growth in case numbers concerned me, but because the case numbers were small compared to the population of Wuhan, I thought that this could be something that we could make go away.

I was worried at the time that it would not go away, though; with every emerging disease, there is some proportion of subclinical infections. This means infections that are not severe enough to get onto the radar of the public health officials keeping track of the disease. I’m used to many emerging diseases looking more deadly than they really are because subclinical cases are often not detected at all. In the case of COVID-19, I thought this might be true too, but I was also worried that if we were only looking at symptomatic, serious cases, we might miss people who were spreading the disease.

These people could then travel the world and spread the disease.

I was worried until I heard the WHO was saying that asymptomatic patients carrying the virus were rare, and also that they did not contribute substantially to the spread of the disease.

It turns out, WHO must have been wrong. Several recent analyses have shown that many of the infections that occur are asymptomatic, and that these asymptomatic infections contribute to the spread of the disease.

For example, this recent paper looks at the “bottle” population on the Diamond Princess, which is about as close as we will get to a field trial of how the virus spreads. As it turns out, just about one-sixth of the passengers aboard tested positive. But what’s more…



John Skylar, PhD

Virologist, author, damn fool. Also found at and Opinions my own, impressions yours.