Yee-Chun Chen, Li-Min Huang, Chang-Chuan Chan, Chan-Ping Su, Shan-Chwen Chang, Ying-Ying Chang, Mei-Ling Chen, Chien-Ching Hung, Wen-Jone Chen, Fang-Yue Lin, Yuan-Teh Lee, and the SARS Research Group of National Taiwan University College of Medicine and National Taiwan University Hospital
Abstract
Thirty-one cases of severe acute respiratory syndrome (SARS) occurred after exposure in the emergency room at the National Taiwan University Hospital. The index patient was linked to an outbreak at a nearby municipal hospital. Three clusters were identified over a 3-week period. The first cluster (5 patients) and the second cluster (14 patients) occurred among patients, family members, and nursing aids. The third cluster (12 patients) occurred exclusively among healthcare workers. Six healthcare workers had close contact with SARS patients. Six others, with different working patterns, indicated that they did not have contact with a SARS patient. Environmental surveys found 9 of 119 samples of inanimate objects to be positive for SARS coronavirus RNA. These observations indicate that although transmission by direct contact with known SARS patients was responsible for most cases, environmental contamination with the SARS coronavirus may have lead to infection among healthcare workers without documented contact with known hospitalized SARS patients.
The coronavirus responsible for the severe acute respiratory syndrome (SARS-CoV) rapidly spread from Mainland China to 30 countries worldwide (1–4). From November 1, 2002, through July 31, 2003, a total of 8,098 probable cases were reported, including 346 from Taiwan (2). The disease is of great concern because of the high case-fatality rate, short incubation period, rapid spread along international air routes, and the large number of cases in previously healthy hospital staff (1,2,5–7). SARS appears to be spread most commonly by close person-to-person contact through exposure to infectious droplets and possibly by direct contact with infected body fluids (1,5–7). Emerging evidence indicates that SARS can be acquired from contaminated inanimate objects in the environment (8).
Taiwan is geographically close to China and Hong Kong and has a population of 23 million. An outbreak began on April 23, 2003, at a municipal hospital (hospital A) in Taipei. The index patient had unrecognized SARS. Multiple patients, visitors, and healthcare workers were exposed to this patient (9). After the outbreak at hospital A, patients sought care at the National Taiwan University Hospital, and patients with febrile illness screened in the emergency room (ER) increased substantially.
On May 8, 2003, we identified and reported to the local health department three SARS cases in patients whose only contact history was being treated at the National Taiwan University Hospital ER. Source and contact tracing failed to identify the index patient. In response to this outbreak, we admitted all ER patients in phases to a special unit where droplet and contact precautions were implemented, and on May 12, 2003, the operation of the ER was suspended.
On the same day, the infection control team was informed that three healthcare workers who worked in the ER had fever. They were immediately isolated, and initial interviews with the healthcare workers failed to identify a common source of infection. To better understand the mode of transmission, we conducted this epidemiologic study and environmental surveillance by using a highly sensitive and specific assay for SARS-CoV RNA. We describe how we traced the index patient to hospital A and the subsequent occurrence of three clusters of SARS after exposure to the National Taiwan University Hospital ER. We also provide evidence for indirect-contact transmission among some of the healthcare workers on the basis of the environmental studies.
