Time-varying transmission dynamics of Novel Coronavirus Pneumonia in China

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Abstract
Rationale: Several studies have estimated basic production number of novel coronavirus pneumonia (NCP). However, the time-varying transmission dynamics of NCP during the outbreak remain unclear.Objectives: We aimed to estimate the basic and time-varying transmission dynamics of NCP across China, and compared them with SARS.Methods: Data on NCP cases by February 7, 2020 were collected from epidemiological investigations or official websites. Data on severe acute respiratory syndrome (SARS) cases in Guangdong Province, Beijing and Hong Kong during 2002-2003 were also obtained. We estimated the doubling time, basic reproduction number (R0) and time-varying reproduction number (Rt) of NCP and SARS.Measurements and main results: As of February 7, 2020, 34,598 NCP cases were identified in China, and daily confirmed cases decreased after February 4. The doubling time of NCP nationwide was 2.4 days which was shorter than that of SARS in Guangdong (14.3 days), Hong Kong (5.7 days) and Beijing (12.4 days). TheR0of NCP cases nationwide and in Wuhan were 4.5 and 4.4 respectively, which were higher thanR0of SARS in Guangdong (R0=2.3), Hongkong (R0=2.3), and Beijing (R0=2.6). TheRtfor NCP continuously decreased especially after January 16 nationwide and in Wuhan. TheR0for secondary NCP cases in Guangdong was 0.6, and theRtvalues were less than 1 during the epidemic.Conclusions: NCP may have a higher transmissibility than SARS, and the efforts of containing the outbreak are effective. However, the efforts are needed to persist in for reducing time-varying reproduction number below one.At a Glance Commentary: Scientific Knowledge on the Subject: Since December 29, 2019, pneumonia infection with 2019-nCoV, now named as Novel Coronavirus Pneumonia (NCP), occurred in Wuhan, Hubei Province, China. The disease has rapidly spread from Wuhan to other areas. As a novel virus, the time-varying transmission dynamics of NCP remain unclear, and it is also important to compare it with SARS.What This Study Adds to the Field: We compared the transmission dynamics of NCP with SARS, and found that NCP has a higher transmissibility than SARS. Time-varying production number indicates that rigorous control measures taken by governments are effective across China, and persistent efforts are needed to be taken for reducing instantaneous reproduction number below one.