Influenza-associated mortality in Hong Kong.
BACKGROUND
The impact of influenza on mortality in countries in subtropical and tropical regions is poorly quantified. Estimation of influenza-related illness in warm-climate regions is more difficult, because the seasonality of virus circulation is less well-defined. Partly as a result of these factors, influenza vaccine is grossly underutilized in the tropics, even for individuals >or=65 years of age.


METHODS
Weekly numbers of deaths were modeled by Poisson regression, and excess deaths attributable to influenza in Hong Kong were estimated for 1996-1999. Comparison of weekly mortality during periods of influenza predominance and periods of low influenza activity was used to derive an alternative estimate of influenza-associated mortality.


RESULTS
Estimates derived from the Poisson model indicated that influenza resulted in 7.3 deaths per 100,000 population per year (95% confidence interval [CI], 3.1-11.4) from cardiorespiratory disease among individuals aged 40-65 years and 102.0 deaths per 100,000 per population per year (95% CI, 61.2-142.7) among individuals aged >or=65 years. Although respiratory diseases accounted for the majority of influenza-related deaths, influenza also contributed to 13.8% (95% CI, 4.8%- 22.7%) and 5.3% (95% CI, 1.2%-9.3%) of deaths related to ischemic heart disease.


CONCLUSIONS
Influenza is associated with deaths due to ischemic heart disease as well from respiratory diseases. Overall influenza-associated mortality in a region with a warm climate, such as Hong Kong, is comparable with that documented in temperate regions. The need for influenza vaccination in tropical regions needs to be reassessed.
Wong
Chit-Ming
CM
Department of Community Medicine, University of Hong Kong, Special Administrative Region of China.
Chan
King-Pan
KP
Hedley
Anthony Johnson
AJ
Peiris
J S Malik
JS
D000328:Adult; D000368:Aged; D002423:Cause of Death; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007251:Influenza, Human / Q000401:mortality*; D008875:Middle Aged