Transmission dynamics of the etiological agent of SARS in Hong Kong: impact of public health interventions.
We present an analysis of the first 10 weeks of the severe acute respiratory syndrome (SARS) epidemic in Hong Kong. The epidemic to date has been characterized by two large clusters-initiated by two separate "super-spread" events (SSEs)-and by ongoing community transmission. By fitting a stochastic model to data on 1512 cases, including these clusters, we show that the etiological agent of SARS is moderately transmissible. Excluding SSEs, we estimate that 2.7 secondary infections were generated per case on average at the start of the epidemic, with a substantial contribution from hospital transmission. Transmission rates fell during the epidemic, primarily as a result of reductions in population contact rates and improved hospital infection control, but also because of more rapid hospital attendance by symptomatic individuals. As a result, the epidemic is now in decline, although continued vigilance is necessary for this to be maintained. Restrictions on longer range population movement are shown to be a potentially useful additional control measure in some contexts. We estimate that most currently infected persons are now hospitalized, which highlights the importance of control of nosocomial transmission.
Riley
Steven
S
Department of Infectious Disease Epidemiology, Faculty of Medicine, Imperial College London, Exhibition Road, London SW7 2AZ, UK. s.riley@imperial.ac.uk
Fraser
Christophe
C
Donnelly
Christl A
CA
Ghani
Azra C
AC
Abu-Raddad
Laith J
LJ
Hedley
Anthony J
AJ
Leung
Gabriel M
GM
Ho
Lai-Ming
LM
Lam
Tai-Hing
TH
Thach
Thuan Q
TQ
Chau
Patsy
P
Chan
King-Pan
KP
Lo
Su-Vui
SV
Leung
Pak-Yin
PY
Tsang
Thomas
T
Ho
William
W
Lee
Koon-Hung
KH
Lau
Edith M C
EM
Ferguson
Neil M
NM
Anderson
Roy M
RM
D016000:Cluster Analysis; D016358:Contact Tracing; D003428:Cross Infection / Q000453:epidemiology / Q000517:prevention & control / Q000635:transmission; D004196:Disease Outbreaks / Q000517:prevention & control / Q000706:statistics & numerical data; D004812:Epidemiologic Methods; D014943:Global Health; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D017053:Infection Control; D008433:Mathematics; D015233:Models, Statistical; D010356:Patient Isolation; D011336:Probability; D015980:Public Health Practice; D011790:Quarantine; D045473:Severe acute respiratory syndrome-related coronavirus / Q000502:physiology; D045169:Severe Acute Respiratory Syndrome / Q000453:epidemiology* / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D013269:Stochastic Processes