FRIDAY, Jan. 31, 2020 (HealthDay News) -- In the early stages, the novel 2019 coronavirus (2019-nCoV)-infected pneumonia (NCIP) epidemic doubled in size every 7.4 days, according to a study published online Jan. 29 in the New England Journal of Medicine.
Qun Li, M.Med., from the Chinese Center for Disease Control and Prevention in Beijing, and colleagues reported the characteristics of cases and estimated the key epidemiologic time-delay distributions for laboratory-confirmed cases of NCIP reported by Jan. 22, 2020.
The researchers found that the median age of the first 425 patients with confirmed NCIP was 59 years, and 56 percent were male. Fifty-five percent of cases with onset before Jan. 1, 2020, and 8.6 percent of subsequent cases were linked to the Huanan Seafood Wholesale Market. There was a 5.2-day mean incubation period; the 95th percentile of distribution was at 12.5 days. The epidemic doubled in size every 7.4 days in its early stages. The basic reproductive number was estimated to be 2.2, with a mean serial interval of 7.5 days.
"We found that cases of NCIP have been doubling in size approximately every 7.4 days in Wuhan at this stage. Human-to-human transmission among close contacts has occurred since the middle of December and spread out gradually within a month after that," the authors write. "Urgent next steps include identifying the most effective control measures to reduce transmission in the community."