Efficiency of quarantine during an epidemic of Severe Acute Respiratory Syndrome—Beijing, China, 2003

Morbidity and Mortality Weekly Report, Oct 31, 2003 by J Ou, Q Li, G Zeng, Z Dun, A Qin

During March--July 2003, an epidemic of severe acute respiratory syndrome (SARS) in Beijing, China, accounted for 2,521 probable cases * (attack rate: 19 per 100,000 population). To control the epidemic, public health officials initiated enhanced surveillance, isolation of SARS patients, use of personal protective equipment (PPE) by health-care workers, and quarantine of contacts of known SARS patients. Approximately 30,000 Beijing residents were quarantined in their homes or quarantine sites. To guide future quarantine policy, the Chinese Field Epidemiology Training Program (China FETP) of the Chinese Center for Disease Control and Prevention (China CDC) conducted a survey to estimate the risk for acquiring SARS among quarantined residents of Haidian District (2001 population: 2.24 million), Beijing, in May 2003, 1 month after the epidemic peaked. This report summarizes the results of that survey, which indicate that, as a component of a comprehensive SARS-control program, quarantine should be limited to persons who have contact with an actively ill SARS patient in the home or hospital, allowing for better focus of resources in future outbreaks.

The 33 precincts in Haidian District were divided into five locations: north (seven precincts), south (six), west (seven), east (six), and central (seven). From each location, the precinct with the greatest number of persons quarantined was selected based on lists from precinct quarantine officers. The selected precincts had 171 (29%) SARS cases and 1,210 (23%) persons quarantined in the district. Quarantined persons were asked to complete a self-administered questionnaire regarding the reasons for quarantine. Quarantined persons and their contacts were categorized as having SARS according to the criteria released by the Chinese Ministry of Health (CMoH). Persons with probable SARS on quarantine and surveillance lists for the precincts and the district were compared with surveyed persons to verify SARS in quarantined persons and their contacts.

In Beijing, contact was defined as 30 minutes' exposure in the following situations to a SARS patient who required quarantine: 1) health-care workers who did not use PPE while evaluating or treating a SARS patient; 2) other persons (e.g., family members) who provided care for a SARS patient; 3) persons who shared the same living quarters as a SARS patient; 4) persons who visited a SARS patient; 5) persons who worked in the same office room or workshop as a SARS patient; 6) classmates or teachers of a SARS patient; and 7) persons using the same public conveyance as a SARS patient (rules varied by conveyance). Quarantine was for 14 days after exposure. Quarantine was initially for persons exposed to a SARS patient [less than or equal to] 14 days before the patient's illness onset, but this period was reduced to 10 and then to 3 days. Travelers who had fever (>100.4 [degrees] F [>38 [degrees] C]) arriving from other SARS-affected cities were placed under personal surveillance ([dagger]) instead of quarantine. All quarantined persons were followed up daily by a home visit or telephone call from the precinct quarantine officer and were given food and, if needed, medicine. If they acquired fever while under quarantine, they were transferred to a hospital for isolation. Some employers paid salaries to their employees under quarantine.

In Haidian District, during March 1-May 23, a total of 5,186 persons (0.23% of 2.24 million residents) were quarantined. During May 26--June 4, a total of 1,210 residents were sampled; 1,028 (85%) completed the questionnaire. A total of 232 (2.3%; 95% confidence interval [CI] = 1.6%-3.5%) residents of the surveyed population (n = 1,010) acquired probable SARS while under quarantine (Table 1). The median quarantine period was 14 days (range: 1-28 days). Only quarantined persons who had a history of contact with a SARS patient acquired SARS during quarantine. In contrast, none of the quarantined persons whose exposure did not involve contact with a SARS patient acquired SARS; these included persons (e.g., a contact of a SARS contact or a contact of a patient with fever only) who had been quarantined mistakenly early in the outbreak before procedures were well known to all quarantine officers. In addition, as hospital isolation of persons under surveillance for SARS was relaxed, these persons required quarantine for potential exposure to an actual SARS patient in the hospital.

Among the 626 (62%) quarantined persons with known contact with persons with probable SARS, those who cared for an actively ill SARS patient had the highest attack rate (Table 2). In contrast, quarantined persons who had contact with a SARS patient before they became ill had no detectable risk (95% CI = 0%-2.8%). In addition, no secondary transmission to relatives or other contacts was detected from persons who had SARS while under quarantine. No SARS patients detected through SARS surveillance reported a history of contact with a person under quarantine.