April 2, 2020

Early transmission dynamics in coronavirus-infected pneumonia patients

By: Judy Mathias

Editor's Note

Human-to-human transmission of novel coronavirus (2019-nCOV)-infected pneumonia (NCIP) has been occurring among close contacts since the middle of December 2019, with the initial cases in Wuhan, China, and the epidemic has been gradually growing in recent weeks, this study finds.

Researchers analyzed the first 425 patients with confirmed NCIP. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market. The mean incubation period was 5.2 days, with 95% of distribution at 12.5 days.

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In its early stages, the number of infected patients doubled in size every 7.4 days, meaning that on average each patient spread infection to 2.2 other people.  

Duration from illness onset to first medical visit for 45 patients with illness onset before January 1 was a mean of 5.8 days, similar to the mean of 4.6 days for 207 patients with illness onset between January 1 and January 11.

The mean duration from onset to hospital admission was 12.5 days in 44 cases with onset before January 1, which was longer than the 9.1 days for 189 patients with illness onset between January 1 and 11.

The researchers say their findings provide important parameters for further analyses, including the impact of control measures and predictions of the future spread of infection.

An accompanying editorial by Anthony S. Fauci, MD, and colleagues, noted that, on the basis of a case definition requiring a diagnosis of pneumonia and assuming the number of asymptomatic or minimally symptomatic cases is several times as high as the number of reported cases, the fatality rate may be considerably less than 1%. Currently the reported fatality rate of coronavirus-infected pneumonia diagnosis is approximately 2%.

The findings also suggest that the overall clinical consequences of COVID-19 may ultimately be more like a severe seasonal influenza (fatality rate, 0.1%) or a pandemic influenza like in 1957 and 1968, rather than a disease similar to SARS and MERS, the authors say.


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