The NEW ENGLAND JOURNAL Of MEDICINE was based on information from 10 cases and is steps include identifving the most effective con somewhat imprecise:it would be important for trol measures to reduce transmission in the urther studies to provide more information on community.The working case definitions may this distribution.When more data become avail- need to be refined as more is learned about the racteristics of NCI， cases four co endemic in humans would es in epidemiology-for example increases be informative. infections among persons in younger age group Our study suffers from the usual limitations or health care workers.Future studies could in of initial investigations of infections with an clude forecasts of the epidemic dynamics and the special stud es of person-to-person transmissior own d th or otne tons,and s eagents.To incr ase the for early detection and diag osis inferences have heen made on a "line list"tha history was considered in the case identification includes detailed individual information on each and has been continually modified once more confirmed case,but there may soon be too many ailable cases to sustain nore easily be lable t The views expe the time for case confirm the initial focus of case detection was on pa d this y ence tients with pneumonia,but we now understand the Natic S and Te that some patients can present with gastrointes- rging and R ing In for In in a chi nas rly infec adation (71934002)the Na inf may clinical severity have been under-ascertaine among the confirmed cases.We did not have detailed information on disease severity for in- ndnpoanof clusion in this analysis. nd that cases of NCII s oximately ever Wu stag nta ha since the middle of December and spread ou gradually within a month after that.Urgent next and Pr the Wor .J.Y.W..T.T .the Chengd a.Hu n (Y.Liu) T.).th iading Di ZD) he er M n District N ENGLJ MED NEJM.ORG The New England Journal of Medicin Downloaded from nejm.ong at SOUTHERN ME 8 n engl j med nejm.org The new england journal o f medicine was based on information from 10 cases and is somewhat imprecise; it would be important for further studies to provide more information on this distribution. When more data become avail￾able on epidemiologic characteristics of NCIP, a detailed comparison with the corresponding characteristics of SARS and MERS, as well as the four coronaviruses endemic in humans, would be informative. Our study suffers from the usual limitations of initial investigations of infections with an emerging novel pathogen, particularly during the earliest phase, when little is known about any aspect of the outbreak and there is a lack of diagnostic reagents. To increase the sensitivity for early detection and diagnosis, epidemiology history was considered in the case identification and has been continually modified once more information has become available. Confirmed cases could more easily be identified after the PCR diagnostic reagents were made available to Wuhan on January 11, which helped us shorten the time for case confirmation. Furthermore, the initial focus of case detection was on pa￾tients with pneumonia, but we now understand that some patients can present with gastrointes￾tinal symptoms, and an asymptomatic infection in a child has also been reported.17 Early infec￾tions with atypical presentations may have been missed, and it is likely that infections of mild clinical severity have been under-ascertained among the confirmed cases.18 We did not have detailed information on disease severity for in￾clusion in this analysis. In conclusion, 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. Urgent next steps include identifying the most effective con￾trol measures to reduce transmission in the community. The working case definitions may need to be refined as more is learned about the epidemiologic characteristics and outbreak dy￾namics. The characteristics of cases should continue to be monitored to identify any chang￾es in epidemiology — for example, increases in infections among persons in younger age groups or health care workers. Future studies could in￾clude forecasts of the epidemic dynamics and special studies of person-to-person transmission in households or other locations, and serosur￾veys to determine the incidence of the subclini￾cal infections would be valuable.14 These initial inferences have been made on a “line list” that includes detailed individual information on each confirmed case, but there may soon be too many cases to sustain this approach to surveillance, and other approaches may be required.19 The views expressed in this article are those of the authors and do not represent the official policy of the China CDC. All the authors have declared no relationships or activities that could appear to have influenced this work. Supported by the Ministry of Science and Technology of Chi￾na, the National Science and Technology Major Projects of China (2018ZX10201-002-008-002, 2018ZX10101002-003), the China– U.S. Collaborative Program on Emerging and Re-emerging In￾fectious Disease, and National Mega-Projects for Infectious Disease (2018ZX10201002-008-002), the National Natural Sci￾ence Foundation (71934002), the National Institute of Allergy and Infectious Diseases (Centers of Excellence for Influenza Research and Surveillance [CEIRS] contract number HH￾SN272201400006C), and the Health and Medical Research Fund (Hong Kong). None of the funders had any role in the study de￾sign and the collection, analysis, and interpretation of data or in the writing of the article and the decision to submit it for publi￾cation. The researchers confirm their independence from funders and sponsors. Disclosure forms provided by the authors are available with the full text of this article at NEJM.org. We thank Wuhan CDC, Huanggang CDC, and other prefec￾ture CDCs and medical institutions in Wuhan for assistance with field investigation administration and data collection and the National Institute for Viral Disease Control and Prevention, China CDC, for assistance with laboratory testing. Appendix The authors’ affiliations are as follows: the Chinese Center for Disease Control and Prevention, Beijing (Q.L., X.W., L.Z., R.R., N.X., C.L., D.L., J.Z., W.T., L.J., Q.W., R.W., Y.Z., G. Shi, G.F.G., Z.F.), the Hubei Provincial Center for Disease Control and Prevention, Wuhan, Hubei (X.G., Y.T., X.X., Y.W., Q.C., M.L., C.C., R.Y., S.Z., Y. Luo, B.Y.), the World Health Organization Collaborating Centre for Infectious Disease Epidemiology and Control, School of Public Health, University of Hong Kong, Hong Kong (P.W., K.S.M.L., E.H.Y.L., J.Y.W., T.T.Y.L., J.T.W., B.J.C., G.M.L.), the Chinese Field Epidemiology Training Program, Chinese Center for Disease Con￾trol and Prevention, Beijing (T.L., R.Y., S.Z., H. Liu, Y. Liu, G. Shao, H. Li, Z.T.), the Jingzhou Center for Disease Control and Preven￾tion, Jingzhou, Hubei (T.L.), the Chengdu Center for Disease Control and Prevention, Chengdu, Sichuan (H. Liu); the Hunan Provincial Center for Disease Control and Prevention, Changsha, Hunan (Y. Liu), the Anyang Municipal Center for Disease Control and Prevention, Anyang, Henan (G. Shao), the Panjin Center for Disease Control and Prevention, Panjin, Liaoning (H. Li), the Guizhou Center for Dis￾ease Control and Prevention, Guiyang, Guizhou (Z.T.), the Jiading District Center for Disease Control and Prevention, Shanghai (Y.Y.), the Nanchang Center for Disease Control and Prevention, Nanchang, Jiangxi (Z.D.), the Inner Mongolia Comprehensive Center for Disease Control and Prevention, Hohhot, Inner Mongolia (B.L.), and the Baoshan District Center for Disease Control and Prevention, Shanghai (Z.M.) — all in China. The New England Journal of Medicine Downloaded from nejm.org at SOUTHERN MEDICAL UNIVERSITY on March 6, 2020. For personal use only. No other uses without permission. Copyright © 2020 Massachusetts Medical Society. All rights reserved