A study led by Zhong Nanshan, head of the high-level expert group appointed by the National Health Commission to fight novel coronavirus has revealed that the incubation period of the virus can be as long as 24 days.

Zhong, corresponding author of the paper published on medRxiv on February 8 elaborated on the finding during an interview with CCTV reporter on Tuesday.

About the team's article on the clinical features of 1,099 patients with novel coronavirus pneumonia, "the study was based on clinical data provided by a total of 552 hospitals in 30 provinces, autonomous regions and municipalities directly under the central government. The research team conducted a comprehensive analysis of the clinical features of the patients," said Zhong.

"There's only one patient who actually reported a 24-day latent period," he said, which means there's only one patient in the 1,099 cases.

It is "not scientific" to take the time of only one patient as the maximum incubation period of the disease, stressed Zhong, and the study shows the median incubation period for all these patients is four days.

Zhong said the article is a preprint server, which requires more peer advice and cannot provide clinical guidance.

"In the preprint version, we use a statistical method to record the incubation period, which is patients' dictation," said the expert. "We calculated the time according to the patient's description of when they contact the source of infection and the earliest onset of symptoms. The longest is 24 days."

The team will report on the interquartile range in the article – two days and seven days respectively, which is more scientific to reflect the overall situation.

Zhong asked the public not to read too much into the information since "the case with 24-day latent period is less than one in a thousand."