N Engl J Med. 2020 Jan 29. doi: 10.1056/NEJMoa2001316.
Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus-Infected Pneumonia.
Li Q1, Guan X1, Wu P1, Wang X1, Zhou L1, Tong Y1, Ren R1, Leung KSM1, Lau EHY1, Wong JY1, Xing X1, Xiang N1, Wu Y1, Li C1, Chen Q1, Li D1, Liu T1, Zhao J1, Li M1, Tu W1, Chen C1, Jin L1, Yang R1, Wang Q1, Zhou S1, Wang R1, Liu H1, Luo Y1, Liu Y1, Shao G1, Li H1, Tao Z1, Yang Y1, Deng Z1, Liu B1, Ma Z1, Zhang Y1, Shi G1, Lam TTY1, Wu JTK1, Gao GF1, Cowling BJ1, Yang B1, Leung GM1, Feng Z1.
Abstract BACKGROUND: The initial cases of novel coronavirus (2019-nCoV)-infected pneumonia (NCIP) occurred in Wuhan, Hubei Province, China, in December 2019 and January 2020. We analyzed data on the first 425 confirmed cases in Wuhan to determine the epidemiologic characteristics of NCIP.
METHODS: We collected information on demographic characteristics, exposure history, and illness timelines of laboratory-confirmed cases of NCIP that had been reported by January 22, 2020. We described characteristics of the cases and estimated the key epidemiologic time-delay distributions. In the early period of exponential growth, we estimated the epidemic doubling time and the basic reproductive number.
RESULTS: Among the first 425 patients with confirmed NCIP, the median age was 59 years and 56% were male. The majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days (95% confidence interval [CI], 4.1 to 7.0), with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days. With a mean serial interval of 7.5 days (95% CI, 5.3 to 19), the basic reproductive number was estimated to be 2.2 (95% CI, 1.4 to 3.9).
CONCLUSIONS: On the basis of this information, there is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019. Considerable efforts to reduce transmission will be required to control outbreaks if similar dynamics apply elsewhere. Measures to prevent or reduce transmission should be implemented in populations at risk. (Funded by the Ministry of Science and Technology of China and others.).Copyright © 2020 Massachusetts Medical Society.
PMID: 31995857 DOI: 10.1056/NEJMoa2001316