In general, experts see three broad reasons for the downward trend in the rate of coronavirus deaths: testing, treatment and a shift in whom the virus is infecting. The relative contribution of these factors is not yet clear. And because death reports can lag diagnoses by weeks, the current rise in coronavirus cases could still portend increases in mortality in the days to come…

Health care workers have also become more knowledgeable about promising treatments and palliative care options to combat the coronavirus and its effects. For instance, prone positioning, in which patients are flipped onto their stomachs, can ease respiratory distress by opening up the lungs. Critically ill individuals are also now known to be vulnerable to excessive blood clotting, and may benefit from blood thinners. And the steroid dexamethasone appears to reduce deaths among patients with severe Covid-19, although the data demonstrating this emerged only recently. (Another drug, an antiviral called remdesivir, seems to speed recovery, but does not appear to have notable effects on mortality.)

“Before, it felt like we were stumbling in the dark,” Dr. Bell said. “It feels a little bit better now.”