Abstract
An outbreak of Severe Acute Respiratory Syndrome (SARS) occurred in Hong Kong in late February 2003, resulting in 8,096 cumulative cases with 774 deaths. The outbreak was amplified by nosocomial transmission in many hospitals. Using mathematical modeling, we simulated the number of new incident and prevalent cases of SARS after one infected person was admitted to a hospital (index case). The simulation was tested stochastically using the SEIR model based on previously reported Gamma distributions. We estimated the duration time until 10 beds in negative pressure rooms in Chiyoda‐ku, one of the 23 wards in Tokyo, were fully occupied with SARS‐infected patients. We determined the impact of an increasing number of days on the number of prevalent cases until the index case was isolated. The prevalent cases increase exponentially along with the increase of the non‐isolation period of the index case, and all the beds were fully occupied if the index case was not isolated until more than 6 days. However even 2 days non‐isolation period of the index case could fill up all the beds when 16% of secondary infections are transmitted outside the hospital. There is a possibility that an epidemic will occur with the isolation of the index case even at early days if the infection is transmitted outside the hospital. The simulation results revealed that it was important to recognize and isolate SARS patients as early as possible and also to prevent the transmission spreading outside the hospital to control an epidemic.
Keywords: SARS, nosocomial transmission, stochastic model, simulation
Abbreviations
- SARS
severe acute respiratory syndrome
- SARS‐CoV
SARS‐associated coronavirus
- SS
super spreader
- SSE
super spread event
- WHO
World Health Organization.
References
- 1. Anderson, R.M. , and May, R.M. 1992. Infectious disease of humans: dynamics and control, Oxford University Press, Oxford. [Google Scholar]
- 2. Centers for Disease Control and Prevention (CDC) 2003. Update: outbreak of severe acute respiratory syndrome— worldwide, 2003. Morb. Mortal. Wkly. Rep. 52: 241–248. [PubMed] [Google Scholar]
- 3. Centers for Disease Control and Prevention (CDC) 2003. Severe acute respiratory syndrome—Singapore, 2003. Morb. Mortal. Wkly. Rep. 52: 405–411. [PubMed] [Google Scholar]
- 4. Chen, Y.C. , Chen, P.J. , Chang, S.C. , Kao, C.L. , Wang, S.H. , Wang, L.H. , Yang, P.C. , And SARS Research Group of National Taiwan University College of Medicine and National Taiwan University Hospital . 2004. Infection control and SARS transmission among healthcare workers, Taiwan. Emerg. Infect. Dis. 10: 895–898. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Donnelly, C.A. , Ghani, A.C. , Leung, G.M. , Hedley, A.J. , Fraser, C. , Riley, S. , Abu‐Raddad, L.J. , Ho, L.M. , Thach, T.Q. , Chau, P. , Chan, K.P. , Lam, T.H. , Tse, L.Y. , Tsang, T. , Liu, S.H. , Kong, J.H. , Lau, E.M. , Ferguson, N.M. , and Anderson, R.M. 2003. Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong. LANCET 361: 1761–1766. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Drosten, C. , Günther, S. , Preiser, W. , Van der Werf, S. , Brodt, H.R. , Becker, S. , Rabenau, H. , Panning, M. , Kolesnikova, L. , Fouchier, R.A. , Berger, A. , Burguière, A.M. , Cinatl, J. , Eickmann, M. , Escriou, N. , Grywna, K. , Kramme, S. , Manuguerra, J.C. , Müller, S. , Rickerts, V. , Stürmer, M. , Vieth, S. , Klenk, H.D. , Osterhaus, A.D. , Schmitz, H. , and Doerr, H.W. 2003. Identification of a novel coronavirus in patients with severe acute respiratory syndrome. N. Engl. J. Med. 348: 1967–1976. [DOI] [PubMed] [Google Scholar]
- 7. Fouchier, R.A. , Kuiken, T. , Schutten, M. , Van Amerongen, G. , Van Doornum, G.J. , Van den Hoogen, B.G. , Peiris, M. , Lim, W. , Stöhr, K. , and Osterhaus, A.D. 2003. Aetiology: Koch's postulates fulfilled for SARS virus. Nature 423: 240. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8. Gopalakrishna, G. , Choo, P. , Leo, Y.S. , Tay, B.K. , Lim, Y.T. , Khan, A.S. , and Tan, C.C. 2004. SARS transmission and hospital containment. Emerg. Infect. Dis. 10: 395–400. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9. Hsu, L.Y. , Lee, C.C. , Green, J.A. , Ang, B. , Paton, N.I. , Lee, L. , Villacian, J.S. , Lim, P.L. , Earnest, A. , and Leo, Y.S. 2003. Severe acute respiratory syndrome (SARS) in Singapore: clinical features of index patient and initial contacts. Emerg. Infect. Dis. 9: 713–717. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10. Ksiazek, T.G. , Erdman, D. , Goldsmith, C.S. , Zaki, S.R. , Peret, T. , Emery, S. , Tong, S. , Urbani, C. , Comer, J.A. , Lim, W. , Rollin, P.E. , Dowell, S.F. , Ling, A.E. , Humphrey, C.D. , Shieh, W.J. , Guarner, J. , Paddock, C.D. , Rota, P. , Fields, B. , DeRisi, J. , Yang, J.Y. , Cox, N. , Hughes, J.M. , LeDuc, J.W. , Bellini, W.J. , Anderson, L.J. , and SARS Working Group. 2003. A novel coronavirus associated with severe acute respiratory syndrome. N. Engl. J. Med. 348: 1953–1966. [DOI] [PubMed] [Google Scholar]
- 11. Le, D.H. , Bloom, S.A. , Nguyen, Q.H. , Maloney, S.A. , Le, Q.M. , Leitmeyer, K.C. , Bach, H.A. , Reynolds, M.G. , Montgomery, J.M. , Comer, J.A. , Horby, P.W. , and Plant, A.J. 2004. Lack of SRAS transmission among public hospital workers, Vietnam. Emerg. Infect. Dis. 10: 265–268. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12. Leung, G.M. , Hedley, A.J. , Ho, L.M. , Chau, P. , Wong, I.O. , Thach, T.Q. , Ghani, A.C. , Donnelly, C.A. , Fraser, C. , Riley, S. , Ferguson, N.M. , Anderson, R.M. , Tsang, T. , Leung, P.Y. , Wong, V. , Chan, J.C. , Tsui, E. , Lo, S.V. , and Lam, T.H. 2004. The epidemiology of severe acute respiratory syndrome in the 2003 Hong Kong Epidemic: an analysis of all 1755 patients. Ann. Intern. Med. 141: 662–673. [DOI] [PubMed] [Google Scholar]
- 13. Marra, M.A. , Jones, S.J. , Astell, C.R. , Holt, R.A. , Brooks‐Wilson, A. , Butterfield, Y.S. , Khattra, J. , Asano, J.K. , Barber, S.A. , Chan, S.Y. , Cloutier, A. , Coughlin, S.M. , Freeman, D. , Girn, N. , Griffith, O.L. , Leach, S.R. , Mayo, M. , McDonald, H. , Montgomery, S.B. , Pandoh, P.K. , Petrescu, A.S. , Robertson, A.G. , Schein, J.E. , Siddiqui, A. , Smailus, D.E. , Stott, J.M. , Yang, G.S. , Plummer, F. , Andonov, A. , Artsob, H. , Bastien, N. , Bernard, K. , Booth, T.F. , Bowness, D. , Czub, M. , Drebot, M. , Fernando, L. , Flick, R. , Garbutt, M. , Gray, M. , Grolla, A. , Jones, S. , Feldmann, H. , Meyers, A. , Kabani, A. , Li, Y. , Normand, S. , Stroher, U. , Tipples, G.A. , Tyler, S. , Vogrig, R. , Ward, D. , Watson, B. , Brunham, R.C. , Krajden, M. , Petric, M. , Skowronski, D.M. , Upton, C. , and Roper, R.L. 2003. The genome sequence of the SARS‐associated coronavirus. Science 300: 1399–1404. [DOI] [PubMed] [Google Scholar]
- 14. Reilley, B. , Van Herp, M. , Sermand, D. , and Dentico, N. 2003. SARS and Carlo Urbani. N. Engl. J. Med. 348: 1951–1952. [DOI] [PubMed] [Google Scholar]
- 15. Riley, S. , Fraser, C. , Donnelly, C.A. , Ghani, A.C. , Abu‐Raddad, L.J. , Hedley, A.J. , Leung, G.M. , Ho, L.M. , Lam, T.H. , Thach, T.Q. , Chau, P. , Chan, K.P. , Lo, S.V. , Leung, P.Y. , Tsang, T. , Ho, W. , Lee, K.H. , Lau, E.M. , Ferguson, N.M. , and Anderson, R.M. 2003. Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions. Science 300: 1961–1966. [DOI] [PubMed] [Google Scholar]
- 16. Thomas, J.C. , and Weber, D.J. 2001. Epidemiologic methods for the study of infectious diseases, Oxford University Press, Oxford. [Google Scholar]
- 17. Tokyo Metropolitan Government. Daytime population density of ward or municipal region (in Japanese). Available from: http://www.toukei.metro.tokyo.jp/tyosoku/ty03za0001.xls.
- 18. Tomlinson, B. , and Cockram, C. 2003. SARS: experience at Prince of Wales Hospital, Hong Kong. LANCET 361: 1486–1487. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19. Webb, G.F. , Blaser, M.J. , Zhu, H. , Ardal, S. , and Wu, J. 2004. Critical role of nosocomial transmission in the Toronto SARS outbreak. Math. Biosci. Eng. 1: 1–13. [DOI] [PubMed] [Google Scholar]
- 20. Wong, T. , Wallington, T. , McDonald, L.C. , Abbas, Z. , Christian, M. , Low, D.E. , Gravel, D. , Ofner, M. , Mederski, B. , Berger, L. , Hansen, L. , Harrison, C. , King, A. , Yaffe, B. , and Tam, T. 2005. Late recognition of SARS in nosocomial outbreak, Toronto. Emerg. Infect. Dis. 11: 322–325. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21. World Health Organization . Summary of probable SARS cases with onset of illness from 1 November 2002 to 31 July 2003. Available from: http://www.who.int/csr/sars/country/table2004_04_21/en/index.html.