But a 1.4 percent case fatality rate still means many deaths. By comparison, the average seasonal flu kills about 0.1 percent of the people it infects in the United States.

The new study calculated estimates based on cases in Wuhan as of Feb. 29, when there had been 48,557 confirmed patients and 2,169 deaths. The risk of death increased with age, “unlike any previously reported pandemic or seasonal influenza,” the researchers wrote.

While the overall symptomatic case fatality rate was 1.4 percent, for people who were 60 and older it was 2.6 percent. That makes the older age group about five times more likely to die than people with symptoms who were 30 to 59 years old, whose risk of dying was 0.5 percent. For those under 30, it was 0.3 percent.

The risk of developing symptomatic infection itself also increased with age, about 4 percent per year for people aged 30 to 60, the study said. The authors estimated that people 60 and older were twice as likely to develop symptoms as people aged 30 to 59 and that people under 30 have about one-sixth the chance of developing symptoms from the infection. That suggests, as has other research, that many young people may be unknowingly infected and able to spread the virus to others.

The researchers noted that their estimates faced some limitations, including that the study would not reflect the many people who were not tested and diagnosed, and that the data might not adequately capture people who were infected in Wuhan and traveled elsewhere. And although their estimated risk of death is lower than previous guesses, the authors make it clear that the virus will undoubtedly leave many casualties in its wake.