OBJECTIVETo explore the characteristics of severe acute respiratory syndrome (SARS) transmission in the population base on analyzing the first imported case and the chains of transmission.

METHODSFor the first imported SARS case and cases who were transmitted by the index case, epidemiological investigations were conducted using the guidelines for surveillance and case investigation issued by the Ministry of Health. Data as the date of onset of symptoms, date of hospitalization, contact history etc. for each of the cases and their close contacts were collected and analyzed.

RESULTSThe first imported SARS case introduced to Beijing had infected 9 people within the family and at the hospital, with two of whom died of the same disease. The incubation period for that index case was 4 days, and that for the cases considered to be the secondary and tertiary generations were 7 and 8 days, respectively. The shorter the incubation period, the longer the fever would last and clinically more severe.

CONCLUSIONOne of the epidemiological characteristics of SARS in Beijing was noticed that the disease clustered in families and hospitals. Infection through droplets and close contact has been viewed as the primary mode of transmission.