The latest tally of almost 1 100 cases of Covid-19 infection from 30 Chinese provinces shows a fatality rate of 1.4% during the early phase of the outbreak.
That's much higher than the rate seen with the seasonal flu, where only about 0.1% of cases end in death. But it's far below the mortality rate of recent coronavirus outbreaks like SARS (9 to 10%) or MERS (36%), noted Dr Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases (NIAID).
Furthermore, the 1.4% figure cited in the new Chinese report, recently published in the New England Journal of Medicine, is probably higher than the "real" death rate, Fauci added.
That's because many coronavirus cases are so mild they're not even being reported, Fauci explained in an editorial he co-wrote in the same issue of the NEJM. Co-authors include Dr. Robert Redfield, who directs the US Centers for Disease Control and Prevention, and Dr Clifford Lane, deputy director of the NIAID.
"If one assumes that the number of asymptomatic or minimally symptomatic cases is several times as high as the number of reported cases, the case fatality rate may be considerably less than 1%," Fauci and his colleagues explained.
"This suggests that the overall clinical consequences of Covid-19 may ultimately be more akin to those of a severe seasonal influenza pandemic [which has a case fatality rate of approximately 0.1%] or a pandemic influenza [similar to those in 1957 and 1968]," the experts wrote.
None of that means that millions of people might not feel miserable for a time as Covid-19 spreads globally. And that spread seems likely from data included in the new Chinese study, which tracked cases up to January 29, Fauci and colleagues said.
The total number of cases globally is now nearly 90 000 and nearly more than 3 000 have died. Sixty cases, most of them coming from people who traveled abroad, have been reported so far in the United States.
But according to the new Chinese study, it's estimated that every person infected with coronavirus spread the germ at a "basic reproduction number" of 2.2.
"Which means that, on average, each infected person spreads the infection to an additional two persons," the NEJM editorialists wrote.
Unless that number falls below 1.0, "it is likely that the outbreak will continue to spread," Fauci and colleagues predicted. They also noted that the coronavirus appears to be at relatively high levels in the mouth and throat even in the very early stages of infection, heightening "concerns about increased infectivity during the period of minimal symptoms."
The three experts added one more nugget gleaned from the Chinese report: For severe cases, the need for hospitalisation appears within a window of about 9 to 12.5 days after first symptoms. That "delay in progression" might give doctors time to intervene and stop the escalation of an illness, the team said.
Still, the bottom line, according to the experts: "Given the efficiency of transmission as indicated in the current [Chinese] report, we should be prepared for Covid-19 to gain a foothold throughout the world, including the United States."
They echoed recent advisories from US health officials that spread in the United States would mean that Americans would begin to employ so-called "mitigation strategies." Those efforts would include standing a safe distance away from obviously sick people, isolating the sick at home or in health care facilities, closing schools and "telecommuting" for work where and when possible.
The new Chinese study was led by Dr N. Zhong, of China's National Clinical Research Center for Respiratory Disease, in Guangdong. It looked at outcomes for 1 100 patients with lab-confirmed Covid-19 who were treated at 552 hospitals in 30 provinces across China, up until January 29.
The study found the average patient was 47, and about 58% were male. About 6% developed disease so severe they required admission to an ICU and/or mechanical ventilation. Fever and cough were the most common symptoms.
"Of note, there were no cases in children younger than 15 years of age," Fauci and colleagues said. "Either children are less likely to become infected… or their symptoms were so mild that their infection escaped detection.
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