Covid-19 death rates are lower worldwide, but no one is sure whether that’s a blip or a trend

“Is this a trend or a blip?” asked Joshua Barocas, an infectious-disease specialist at the Boston University School of Medicine. “Nobody really knows.”

The mortality rate of the coronavirus has been a moving target since the outbreak began.

Early reports out of China put it as high as 7 percent. But that was based mostly on hospitalized patients, and by the time the wave hit the United States, epidemiologists believed it was closer to 2 to 3 percent. Now, factoring in asymptomatic infections, as well as mild cases that might not be part of official tallies, the Centers for Disease Control and Prevention puts the mortality rate at 0.65 percent.

Barocas emphasized that even the lowest estimates represent the potential for millions more deaths. The United States already has the highest number of cases in the world and the most recorded deaths of any country. Though its 330 million people represent roughly 4.25 percent of the world’s population, the country has recorded just over 20 percent of deaths from covid-19, the disease caused by the coronavirus. ...

Public health officials cite multiple reasons for the lower death rates: They note a shift in the demographics of who is being stricken with the virus, with younger people making up the bulk of new infections. More widespread testing is capturing a more diverse range of people and illness, and improved treatment strategies that include antivirals and steroids are saving more lives. ...