Influenza-associated morbidity in subtropical Taiwan.
OBJECTIVE
The purpose of this study was to assess the characteristics of influenza-associated morbidity in subtropical Taiwan, corresponding to the seasonal patterns, weather, and co-circulation of influenza (sub)types, and other respiratory viruses, where the burden of influenza is poorly quantified.


METHODS
This study applied the virus variation-guided Poisson seasonal regression models to evaluate the impact of epidemic influenza on morbidity in Taiwan for 1999-2006. The models allow for the adjusting of influenza-associated morbidity for factors such as annual trend, seasonality, temperature, relative humidity, influenza A (H1N1), A (H3N2), B, and respiratory syncytial virus.


RESULTS
Influenza-associated morbidity was associated more strongly with temperature than relative humidity. Influenza A (H3N2) was more coordinated with other virus (sub)types than A (H1N1). Type B dominated simultaneously with A (H3N2) at times, whereas A (H3N2) and A (H1N1) rarely dominated simultaneously with each other. Epidemiologically, A (H3N2) appeared to be the dominant subtype (51%), followed by type B (39%) and then A (H1N1) (10%) for influenza-associated morbidity.


CONCLUSIONS
This study suggests that seasonality and influenza (sub)types contribute significantly to influenza morbidity in subtropical Taiwan. This is important for influenza control managers who are involved actively in using epidemic and climate information to achieve influenza-reduction targets in subtropical regions.
Liao
Chung-Min
CM
Department of Bioenvironmental Systems Engineering, National Taiwan University, Taipei 10617, Taiwan. cmliao@ntu.edu.tw
Chang
Szu-Yuan
SY
Chen
Szu-Chieh
SC
Chio
Chia-Pin
CP
D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000302:isolation & purification*; D053122:Influenza A Virus, H3N2 Subtype / Q000302:isolation & purification*; D009981:Influenza B virus / Q000302:isolation & purification*; D007251:Influenza, Human / Q000453:epidemiology* / Q000821:virology; D009017:Morbidity; D016012:Poisson Distribution; D011159:Population Surveillance; D018357:Respiratory Syncytial Virus Infections / Q000453:epidemiology / Q000821:virology; D018113:Respiratory Syncytial Virus, Human / Q000302:isolation & purification; D012621:Seasons; D013624:Taiwan / Q000453:epidemiology; D014329:Tropical Climate