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A case-control study was conducted to examine the relationship between severe acute respiratory syndrome (SARS) and the time-dependent precautionary behaviors taken during an outbreak of SARS in Hanoi French Hospital (HFH), Vietnam. Masks (odds ratio [OR] = 0.3; 95% confidence interval [CI]: 0.1, 0.7) and gowns (OR = 0.2; 95% CI: 0.0, 0.8) appeared to prevent SARS transmission. The proportion of doctors and nurses who undertook each measure significantly improved (
2 = 9.8551, P = 0.043) after the onset of secondary cases. The impact of individual behaviors on an outbreak was investigated through mathematical approaches. The reproduction number decreased from 4.1 to 0.7 after notification. The basic reproduction number was estimated, and the use of masks alone was shown to be insufficient in containing an epidemic. Intuitive results obtained by means of stochastic individual-based simulations showed that rapid improvements in behavior and isolation would increase the probability of extinction.
Received August 3, 2004. Accepted for publication January 19, 2005.
Acknowledgments: H.N. would like to pay his respects to Dr. Carlo Urbani, an Italian epidemiologist who worked for the WHO Office in Hanoi, whose great achievements in controlling SARS in HFH inspired this study. The authors are grateful to Profs. Masayuki Kakehashi (Hiroshima University, Japan), Minato Nakazawa (Gunma University, Japan), and Klaus Dietz (University of Tubingen, Germany) for their helpful comments and discussions. The authors would also like to thank Dr. Nguyen Le Hang, Ms. Pham Thi Phuong Thuy, and Ms. Nguyen Thi Thu Ha for their help in our survey. H.N. is also grateful to the Japanese Foundation for AIDS Prevention for supporting his stay in the United Kingdom.
Financial support: The study was partly supported by a Health and Labor Sciences Research Grant for "Special Research" entitled "Research on the nosocomial transmission of SARS" awarded by the Ministry of Health, Labor and Welfare, Japan.
* Address correspondence to Tadatoshi Kuratsuji, Research Institute, International Medical Center of Japan, Toyama 1-21-1, Shinjuku-ku, Tokyo, 162-8655, Japan. E-mail: kuratsuji{at}ri.imcj.go.jp
Authors addresses: Hiroshi Nishiura and Roy M. Anderson, Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Norfolk Place, London, W2 1PG, United Kingdom. Tadatoshi Kuratsuji, Naoto Keicho, Teruo Kirikae, and Takehiko Sasazuki, Research Institute, International Medical Center of Japan, Toyama 1-21-1, Shinjuku-ku, Tokyo, 162-8655, Japan. Tran Quy and Nguyen Chi Phi, Bach Mai Hospital, Giai Phong Street, Hanoi, Vietnam. Vo Van Ban, Hanoi French Hospital, 1 Phuong Mai Street, Dong Da, Hanoi, Vietnam. Le Dang Ha, National Institute for Clinical Research in Tropical Medicine, Bach Mai Hospital, Giai Phong Street, Hanoi, Vietnam. Hoang Thuy Long, National Institute of Hygiene and Epidemiology, 1 Yersin Street, Hanoi, Vietnam. Hiroshi Nishiura and Hideki Yanai, The Research Institute of Tuberculosis, Japan Anti-Tuberculosis Association, Matsuyama 3-1-24, Kiyoseshi, Tokyo, 204-8533, Japan.
Reprint requests: Tadatoshi Kuratsuji, Research Institute, International Medical Center of Japan, 1-21-1, Toyama Shinjuku-ku, Tokyo, 162-8655, Japan, Telephone: 81-3-3202-7181, Fax: 81-3-5273-4526, E-mail: kuratsuji{at}ri.imcj.go.jp.
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