BEIJING — In a report published Wednesday by the New England Journal of Medicine, Chinese scientists describe evidence that the new virus has spread person-to-person among close contacts since mid-December.
Based on the first 425 confirmed cases, they estimate that each infection led to 2.2 others on average. That’s a bit more than ordinary flu but far less than some other respiratory diseases, such as whooping cough and tuberculosis. The rate for SARS, a cousin to the new virus, was estimated to be 3.
The researchers write that “considerable efforts” will be needed to control the virus from spreading if this ratio holds up elsewhere. The average incubation period is five days.
More than half of the cases in which symptoms began before Jan. 1 were tied to a seafood market, but only 8% of cases after that have been.
The virus has sickened thousands of people, and more than 100 have died. A vast majority of the cases and all deaths have been in China.
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