The NEW ENGLAND JOURNAL Of MEDICINE INCE DECEMBER 2019.AN INCREASING Data were collected onto standardized form number of cases of novel coronavirus through interviews of infected persons,rela (2019-nCoV)-infected pneumonia (NCIP tives,close and health care wor have been identified in Wuhan,a large city of 11 ts to clinical fac an es.Ep ata wer Market were identified hy local hospitals using surveillance mechanism for"pneumonia of un fection and their relatives where necessary to known etiology"that was established in the wake determine exposure histories during the 2 weeks of the 2003 severe acute respiratory syndrom before the illness onset,including the dates,time (SARS outbre k with the aim of allowing timel ncy,and patter to any wil d tion c suc H.espec se cities and in e than es to dozen countries around the worlds Her ments such as that specific market or other we provide an analysis of data on the first 425 lab markets.Information about contact with other oratory-confirmed cases in Wuhan to describe the with similar symptoms was also included.A epidemiologic characteristics and transmission epidemiologic info ation collecte during fiel NCI ng exposure METHODS ces.Households a and nlace SOURCES OF DATA have heen visited by the patients in the 2 weel The earliest cases were identified through the before the onset of illness were also investigated 'pneumonia of unknown etiology"surveillance to assess for possible animal and environmenta mechanism.P own etiology i exposures ata were ve pa in dup d were ver ed with Epi 38C)radio Da nia low or normal white-cell count or low lym CASE DEFINITIONS ohocyte count,and no symptomatic improven The initial working case definitions for suspected after antimicrobial treatment for 3 to 5 days fol- NCIP were based on the SARS and Middle East lowing standard clinical guidelines.In respons to th rea by th de 2012 de on 32020 fulfilled all th sing the case definitions des with or without remperature:radio a suspected case was identified,the joint field graphic evidence of pneumonia;low or normal epidemiology team comprising members from white-cell count or low lymphocyte count;and the Chine Center for Disease Co ntrol and Pre trea nt for 3 ay ed field in ions and collect resniratory specimens for to the Huanan Seafood Wholesale Marke t or cor tralized testing at the national institute for viral tact with other patients with similar symntom Disease Control and Prevention.China CDC.in The epidemiologic criteria to define a suspectec case were update d on January 18.2020.once CDO sconducted detailed fie information on ide ses becam for all suspected and confirmec ng:a t N ENGLJ MED NEJM.ORG The New En and Journal of Medicin oaded from nejm.M All right 2 n engl j med nejm.org The new england journal o f medicine S ince December 2019, an increasing number of cases of novel coronavirus (2019-nCoV)–infected pneumonia (NCIP) have been identified in Wuhan, a large city of 11 million people in central China.1-3 On December 29, 2019, the first 4 cases reported, all linked to the Huanan (Southern China) Seafood Wholesale Market, were identified by local hospitals using a surveillance mechanism for “pneumonia of un￾known etiology” that was established in the wake of the 2003 severe acute respiratory syndrome (SARS) outbreak with the aim of allowing timely identification of novel pathogens such as 2019- nCoV.4 In recent days, infections have been iden￾tified in other Chinese cities and in more than a dozen countries around the world.5 Here, we provide an analysis of data on the first 425 lab￾oratory-confirmed cases in Wuhan to describe the epidemiologic characteristics and transmission dynamics of NCIP. Methods Sources of Data The earliest cases were identified through the “pneumonia of unknown etiology” surveillance mechanism.4 Pneumonia of unknown etiology is defined as an illness without a causative patho￾gen identified that fulfills the following criteria: fever (≥38°C), radiographic evidence of pneumo￾nia, low or normal white-cell count or low lym￾phocyte count, and no symptomatic improvement after antimicrobial treatment for 3 to 5 days fol￾lowing standard clinical guidelines. In response to the identification of pneumonia cases and in an effort to increase the sensitivity for early de￾tection, we developed a tailored surveillance proto￾col to identify potential cases on January 3, 2020, using the case definitions described below.1 Once a suspected case was identified, the joint field epidemiology team comprising members from the Chinese Center for Disease Control and Pre￾vention (China CDC) together with provincial, local municipal CDCs and prefecture CDCs would be informed to initiate detailed field investiga￾tions and collect respiratory specimens for cen￾tralized testing at the National Institute for Viral Disease Control and Prevention, China CDC, in Beijing. A joint team comprising staff from China CDC and local CDCs conducted detailed field investigations for all suspected and confirmed 2019-nCoV cases. Data were collected onto standardized forms through interviews of infected persons, rela￾tives, close contacts, and health care workers. We collected information on the dates of illness onset, visits to clinical facilities, hospitalization, and clinical outcomes. Epidemiologic data were collected through interviews and field reports. Investigators interviewed each patient with in￾fection and their relatives, where necessary, to determine exposure histories during the 2 weeks before the illness onset, including the dates, times, frequency, and patterns of exposures to any wild animals, especially those purportedly available in the Huanan Seafood Wholesale Market in Wuhan, or exposures to any relevant environ￾ments such as that specific market or other wet markets. Information about contact with others with similar symptoms was also included. All epidemiologic information collected during field investigations, including exposure history, time￾lines of events, and close contact identification, was cross-checked with information from mul￾tiple sources. Households and places known to have been visited by the patients in the 2 weeks before the onset of illness were also investigated to assess for possible animal and environmental exposures. Data were entered into a central da￾tabase, in duplicate, and were verified with Epi￾Data software (EpiData Association). Case Definitions The initial working case definitions for suspected NCIP were based on the SARS and Middle East respiratory syndrome (MERS) case definitions, as recommended by the World Health Organization (WHO) in 2003 and 2012.6-8 A suspected NCIP case was defined as a pneumonia that either fulfilled all the following four criteria — fever, with or without recorded temperature; radio￾graphic evidence of pneumonia; low or normal white-cell count or low lymphocyte count; and no reduction in symptoms after antimicrobial treatment for 3 days, following standard clinical guidelines — or fulfilled the abovementioned first three criteria and had an epidemiologic link to the Huanan Seafood Wholesale Market or con￾tact with other patients with similar symptoms. The epidemiologic criteria to define a suspected case were updated on January 18, 2020, once new information on identified cases became available. The criteria were the following: a travel history to Wuhan or direct contact with patients from 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