Covid-19 Case Counts Have Been Spiking for Weeks. Why Aren’t Deaths?

Experts say a handful of variables explain the apparent disconnect between cases and deaths

Medical staff push a stretcher with a deceased Covid-19 patient to a car outside of the United Memorial Medical Center on June 30, 2020 in Houston, Texas. Photo: Go Nakamura/Stringer/Getty Images

After slowly gathering momentum during the first quarter of the year, the number of U.S. Covid-19 cases and deaths surged in early April. By the middle of that month, more than 30,000 Americans were testing positive for the novel coronavirus every day, and roughly 2,500 were dying, according to figures from the U.S. Centers for Disease Control and Prevention.

But then, for a time, that initial wave seemed to be breaking. Daily case counts declined as spring turned into summer. Deaths fell steadily. But these encouraging trends didn’t last. A second wave of cases — or maybe just a resurgence of the initial wave — began around the middle of June. Case counts have since increased sharply and show no sign of slowing.

On July 9, there were nearly 65,000 new daily cases of Covid-19 — roughly double the late-April average. But deaths have not followed suit. While the last week has witnessed an uptick in deaths from the June nadir, line graphs of deaths are no longer mirroring the line graphs of new cases.

That may change any day. There is usually a one- or two-week lag between a rise in cases and an associated rise in deaths, says Stephen Morse, PhD, a professor of epidemiology and infectious disease at Columbia University’s Mailman School of Public Health. And in some of the newly hard-hit states, including Texas and Arizona, deaths have begun to increase.

But given the mid-June timing of the caseload spike, we’re now well beyond the one-to-two-week lag period that Morse described. And, according to a news report from the American Medical Association, the virus’s springtime peak saw roughly 2,500 deaths for every 30,000 new diagnoses. The most recent figures reveal a much more encouraging ratio — one on the order of 1,000 deaths per 60,000 new diagnoses.

So what explains the apparent disconnect between cases and deaths? Expanded testing capacity may be one contributing factor, although alone it can’t account for the size of the discrepancy. Experts say a handful of variables may be at play.

“We’ve also learned…