#VisualAbstract: Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia

1. Analysis of the initial transmission dynamics of the novel corononvirus revealed the epidemic to be doubling in size approximately every week with each infected individual having transmitted the disease to 2.2 other persons on average.

2. Mean incubation period was estimated to be 5.2 days, with the 95^th percentile of distribution being 12.5 days, supporting a 14-day medical observation or quarantine period for exposed persons.

Evidence Rating: 2 (Good)

Study Rundown: The novel coronavirus, or 2019-nCoV, represents one of the largest epidemic outbreaks in recent memory, with nearly 100,000 cases have been reported worldwide in over 70 countries. In this study, initial cases of 2019-nCoV were analysed to provide valuable epidemiological information regarding the virus’s early transmission dynamics into becoming an epidemic. Analysis of the first 425 confirmed cases of confirmed 2019-nCoV –infected pneumonia revealed a greater proportion of male versus female patients (56%), and few cases to have affected children, with the median age of patients to be 59 years (range, 15 to 89).

While zoonotic and environmental exposures remain possible routes of transmission, the study strongly reinforced human-to-human transmission to have been occurring and as a primary source of epidemic development. Specifically, it was estimated that each patient was on average spreading the disease to 2.2 other people, contributing to a doubling rate of 7.4 days. Using the data among 10 confirmed cases, the mean incubation period was estimated to be 5.2 days, with the 95^th percentile of distribution being 12.5 days, supporting 2 week observation or quarantine period for exposed individuals. Finally, mean duration from illness onset to medical visit was estimated to be 5.8 days, and mean duration to admission 12.5 days. While the study’s inclusion criteria to focus on more severe cases of the virus (i.e., those requiring significant medical attention) limits the ability of the study to fully characterize transmission dynamics, this study provides invaluable data for further analysis and represents an important step in further outbreak prevention.

Click to read the study in NEJM

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