Only one patient infected with the new strain of the coronavirus was found to have an incubation period of as much as 24 days, a scientist said Tuesday.

The time between initial exposure and development of the first symptoms of the illness is based on the patient’s account of the illness.

Zhong Nanshan, a prominent scientist who is leading a government-appointed panel of experts to help control the coronavirus outbreak, said caution is needed because there’s not enough evidence to regard 24 days as the longest incubation period for the novel coronavirus, Xinhua reported.

The median incubation period is three days, less than the estimated 5.2 days, according to the research conducted by Zhong and his team, whose findings were published on Sunday on medRxiv, the free online archive and distribution server for complete but unpublished medical papers.

The research is based on a sample of 1,099 coronavirus patients selected from 552 hospitals throughout China. The median age of the patients is 47.

Zhong stressed that only one patient reported a 24-day incubation period.

More research and comments from other doctors is needed.

“The information in the paper should not be overinterpreted,” Zhong said.