The effective reproduction number of pandemic influenza: prospective estimation.
BACKGROUND
Timely estimation of the transmissibility of a novel pandemic influenza virus was a public health priority in 2009.


METHODS
We extended methods for prospective estimation of the effective reproduction number (Rt) over time in an emerging epidemic to allow for reporting delays and repeated importations. We estimated Rt based on case notifications and hospitalizations associated with laboratory-confirmed pandemic (H1N1) 2009 virus infections in Hong Kong from June through October 2009.


RESULTS
Rt declined from around 1.4-1.5 at the start of the local epidemic to around 1.1-1.2 later in the summer, suggesting changes in transmissibility perhaps related to school vacations or seasonality. Estimates of Rt based on hospitalizations of confirmed H1N1 cases closely matched estimates based on case notifications.


CONCLUSIONS
Real-time monitoring of the effective reproduction number is feasible and can provide useful information to public health authorities for situational awareness and calibration of mitigation strategies.
Cowling
Benjamin J
BJ
Infectious Disease Epidemiology Group, School of Public Health, The University of Hong Kong, Hong Kong Special Administrative Region, China. bcowling@hku.hk
Lau
Max S Y
MS
Ho
Lai-Ming
LM
Chuang
Shuk-Kwan
SK
Tsang
Thomas
T
Liu
Shao-Haei
SH
Leung
Pak-Yin
PY
Lo
Su-Vui
SV
Lau
Eric H Y
EH
D004196:Disease Outbreaks; D006723:Hong Kong / Q000453:epidemiology; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000635:transmission / Q000821:virology; D011159:Population Surveillance / Q000379:methods; D011446:Prospective Studies
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