Is the Coronavirus Incubation Period Longer Than Previously Believed?

By Juliet Song

There is now a question of whether coronavirus has a longer incubation period than previously believed.

Chinese media now reports that one patient was diagnosed 42 days after she returned home from Wuhan. A new study, led by Zhong Nanshan, China’s top coronavirus expert, found one patient with an incubation period as long as 24 days. Zhong is a renowned scientist that helped control the SARS outbreak in 2003.

But a U.S. expert remains skeptical. “We’d like to know how it is they can be so sure that there were not other exposures of those individuals to the coronavirus,” said Dr. William Schaffner, infectious disease specialist at Vanderbilt University Medical Center, “because such a long incubation period would undoubtedly present a larger challenge to the whole public health effort.”

The frequency of the long incubation period is also in question. “It may only happen very, very rarely. But regardless, if that is possible. It makes the public health effort more difficult,” said Dr. Schaffner.

Chinese officials have said that coronavirus patients can be infectious before showing symptoms, but Dr. Schaffner says that hasn’t been confirmed by the United States since American scientists haven’t seen China’s data.

Although it’s biologically plausible, the question is whether it’s common for the virus to spread that way, or if it only happens occasionally.

For now, it’s still unclear.