A new study reports that people who became sick from the coronavirus in the Chinese city where the outbreak began likely had a lower death rate than previously thought.

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The New York Times reports that the study, published today in Nature Medicine, calculated that people with coronavirus symptoms in Wuhan had a 1.4% likelihood of dying. Some previous estimates have ranged from 2% to 3.4%.

Assessing the risk of death in Wuhan is instructive because it provides a snapshot of the epidemic from the beginning, when doctors were scrambling to treat people with the brand new virus and hospitals were overwhelmed. Some experts say that such a benchmark, known as the symptomatic case fatality rate, could be lower in other countries if measures like widespread business and school closures and appeals for social distancing have the desired effect of slowing the spread of the disease.

The study authors, who include scientists from the Harvard T H Chan School of Public Health and the University of Hong Kong, wrote “The experience gained from managing those initial patients and the increasing availability of newer, and potentially better, treatment modalities to more patients would presumably lead to fewer deaths, all else being equal.”

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

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

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

The study said the risk of developing symptomatic infection itself also increased with age, about 4% per year for people aged between thirty and sixty. The authors estimated that people aged sixty and older were twice as likely to develop symptoms as people aged between thirty and fifty nine, and that people under thirty 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 travelled 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.

The researchers wrote that the findings “indicate that Covid-19 transmission is difficult to control…we might expect at least half of the population to be infected, even with aggressive use of community mitigation measures.”