Li Q, Guan X, Wu P, et al. - Researchers analyzed data on the first 425 confirmed cases of coronavirus in Wuhan to ascertain the epidemiologic characteristics of coronavirus (2019-nCoV)–infected pneumonia (NCIP). They obtained information on demographic characteristics, exposure history, and illness timelines of laboratory-confirmed cases of NCIP that had been reported by January 22, 2020. The characteristics of the cases were defined, and the key epidemiologic time-delay distributions were calculated. The epidemic doubling time and the basic reproductive number were calculated in the early period of exponential growth. There was evidence of human-to-human transmission among close contacts since mid-December 2019. Significant measures to reduce transmission will be required to control outbreaks if similar dynamics occur elsewhere.