COVID-19’s second wave?

If COVID-19 followed the same pattern, we could expect another, and much worse, wave of coronavirus in the fall with three times as many deaths as we’ve seen so far. It would be reasonable to consider panicking. But don’t panic yet. According to no less an authority than Anthony Fauci, a second wave is not inevitable. We need to compare the public reactions to the pandemics of 1918–19 and of 2020 before we accept that a giant second wave of COVID-19 is inescapable.

In the first, ongoing wave of coronavirus, social distancing measures have succeeded in saving millions of lives and flattening the curve. According to a recent article published in Nature, in six countries studied, including the United States, over 60 million COVID-19 infections were prevented thanks to shutdowns. Some countries, most successfully New Zealand, kept these controls in place until the virus was essentially eliminated, allowing the country to re-open completely. Importantly, these measures were more stringently formulated and more consistently applied than anything any city undertook in 1918.

But concerns in the US about the struggling economy have spurred many states to speed through the suggested phases of reopening. Along with a combination of the Memorial Day weekend celebrations and disregard of social distancing practices, this rapid reopening has led to an increase in new daily COVID-19 cases in over 20 states. An epidemiologist at Vanderbilt University Medical Center explained that what we are seeing in the US is a “constant chain of smaller spikes.” In other words, we are not looking at large, cresting waves like those seen during the 1918 flu pandemic, but rather an ongoing series of outbreaks in places where measures to curb the virus’s spread are relaxed or absent.

And that means the eventual arrival—or not—of a second wave depends entirely on us. If you’d like to explore the possible scenarios, I suggest sharing these graphs, prepared by a statistician at the University of Strathclyde, with your students. The take-home message is that our behavior affects the coronavirus’s reproductive number R (average number of new cases caused by one infected individual), which in turn predicts whether outbreaks will grow exponentially into a huge wave, come and go in smaller waves, or fade out altogether.

The question on our minds therefore shouldn’t be “Will there be a second wave?” but rather “What measures do we need to take to keep outbreaks local and manageable?”

Maybe that’s not very satisfying. It doesn’t make good headlines and it sounds much less dramatic. But by working through scenarios about how our behavior affects R and how that plays out in terms of how fast the virus spreads, we can all begin to understand that catchphrases like “second wave” do not begin to capture the complexity of the situation. The term “second wave” misleadingly implies that we have successfully beaten COVID-19 once and that we may or may not have to try to do so again, but the reality is that we continue to fight local battles daily. How we approach that task will go a long way towards determining what happens in the coming months.

There is light at the end of the tunnel. We know how to contain the virus: masks, appropriate social distancing, avoidance of crowded indoor venues, and lots of testing followed by contact tracing. These practices, along with hand-washing and proper hygiene, are the only certainties we have. So, if you haven’t learned the words to “the hand-washing song” at this point, it might be time—we’re going to be singing it for a while.