Description of the 2003 Severe Acute Respiratory Syndrome Outbreak in Hong Kong

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The summary below is from the full report titled "The Epidemiology of Severe Acute Respiratory Syndrome in the 2003 Hong Kong Epidemic: An Analysis of All 1755 Patients." It is in the 2 November 2004 issue of Annals of Internal Medicine (volume 141, pages 662-673). The authors are G.M. Leung, A.J. Hedley, L.-M. Ho, P. Chau, I.O.L. Wong, T.Q. Thach, A.C. Ghani, C.A. Donnelly, C. Fraser, S. Riley, N.M. Ferguson, R.M. Anderson, T. Tsang, P.-Y. Leung, V. Wong, J.C.K. Chan, E. Tsui, S.-V. Lo, and T.-H. Lam.

What is the problem and what is known about it so far?

The severe acute respiratory syndrome (SARS) is a serious, sometimes fatal, illness caused by a virus called coronavirus. First described in Asia in 2002, SARS was discovered in Chinese patients who had fever and severe breathing problems. In spring 2003, SARS quickly spread among humans with close person-to-person contact. More than 8000 people in Asia, Europe, and North and South America became sick with SARS. Some places, such as Hong Kong, set up emergency clinics to handle the large numbers of patients with the illness. Few studies have fully described what happened during the outbreak and the rapid spread of the infection.

Why did the researchers do this particular study?

To describe the 2003 outbreak of SARS in Hong Kong.

Who was studied?

All 1755 reported cases of SARS in Hong Kong in 2003.

How was the study done?

The researchers reviewed a data set that contained information about all patients reported to have SARS who were hospitalized in Hong Kong during the 2003 outbreak. The data set included information about patients' residence and contacts, type and timing of presenting symptoms, blood work, and outcomes. The researchers examined the data to see where most infections occurred and how the virus spread.

What did the researchers find?

Most cases clustered in hospitals and residential buildings. Close human contact and spread through a sewage system probably explained the clustering. Almost one quarter of the infected patients were health care workers. The outbreak lasted about 3 months. The estimated mean incubation period of the viral infection was 4.6 days, and 17% of the patients died. Factors associated with increased risk for death included older age and male sex.

What were the limitations of the study?

The investigators obtained study data from reviewing records. Some patients may have had symptoms and findings or may have received treatments that were not recorded in the records. The presentation and course of SARS may be different in settings that are not large outbreaks.

What are the implications of the study?

The SARS coronavirus may not spread easily and rapidly, except in settings of close contact or exposure to contaminated waste.