title: Epidemiological determinants of spread of causal agent of severe acute respiratory syndrome in Hong Kong.
abstract: BACKGROUND
  Health authorities worldwide, especially in the Asia Pacific region, are seeking effective public-health interventions in the continuing epidemic of severe acute respiratory syndrome (SARS). We assessed the epidemiology of SARS in Hong Kong.
  
  
  METHODS
  We included 1425 cases reported up to April 28, 2003. An integrated database was constructed from several sources containing information on epidemiological, demographic, and clinical variables. We estimated the key epidemiological distributions: infection to onset, onset to admission, admission to death, and admission to discharge. We measured associations between the estimated case fatality rate and patients' age and the time from onset to admission.
  
  
  RESULTS
  After the initial phase of exponential growth, the rate of confirmed cases fell to less than 20 per day by April 28. Public-health interventions included encouragement to report to hospital rapidly after the onset of clinical symptoms, contact tracing for confirmed and suspected cases, and quarantining, monitoring, and restricting the travel of contacts. The mean incubation period of the disease is estimated to be 6.4 days (95% CI 5.2-7.7). The mean time from onset of clinical symptoms to admission to hospital varied between 3 and 5 days, with longer times earlier in the epidemic. The estimated case fatality rate was 13.2% (9.8-16.8) for patients younger than 60 years and 43.3% (35.2-52.4) for patients aged 60 years or older assuming a parametric gamma distribution. A non-parametric method yielded estimates of 6.8% (4.0-9.6) and 55.0% (45.3-64.7), respectively. Case clusters have played an important part in the course of the epidemic.
  
  
  CONCLUSIONS
  Patients' age was strongly associated with outcome. The time between onset of symptoms and admission to hospital did not alter outcome, but shorter intervals will be important to the wider population by restricting the infectious period before patients are placed in quarantine.
authors.affiliation: Department of Infectious Disease Epidemiology, Imperial College, London, UK. c.donnelly@imperial.ac.uk <c.donnelly@imperial.ac.uk>
authors.forename: Christl A
authors.initials: CA
authors.lastname: Donnelly
authors.forename: Azra C
authors.initials: AC
authors.lastname: Ghani
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Leung
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Hedley
authors.forename: Christophe
authors.initials: C
authors.lastname: Fraser
authors.forename: Steven
authors.initials: S
authors.lastname: Riley
authors.forename: Laith J
authors.initials: LJ
authors.lastname: Abu-Raddad
authors.forename: Lai-Ming
authors.initials: LM
authors.lastname: Ho
authors.forename: Thuan-Quoc
authors.initials: TQ
authors.lastname: Thach
authors.forename: Patsy
authors.initials: P
authors.lastname: Chau
authors.forename: King-Pan
authors.initials: KP
authors.lastname: Chan
authors.forename: Tai-Hing
authors.initials: TH
authors.lastname: Lam
authors.forename: Lai-Yin
authors.initials: LY
authors.lastname: Tse
authors.forename: Thomas
authors.initials: T
authors.lastname: Tsang
authors.forename: Shao-Haei
authors.initials: SH
authors.lastname: Liu
authors.forename: James H B
authors.initials: JH
authors.lastname: Kong
authors.forename: Edith M C
authors.initials: EM
authors.lastname: Lau
authors.forename: Neil M
authors.initials: NM
authors.lastname: Ferguson
authors.forename: Roy M
authors.initials: RM
authors.lastname: Anderson
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks / Q000706:statistics & numerical data*; D018450:Disease Progression; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D007223:Infant; D016013:Likelihood Functions; D008297:Male; D008875:Middle Aged; D011790:Quarantine / Q000379:methods / Q000706:statistics & numerical data; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D015996:Survival Rate