The role of imported cases and favorable meteorological conditions in the onset of dengue epidemics.
BACKGROUND
Travelers who acquire dengue infection are often routes for virus transmission to other regions. Nevertheless, the interplay between infected travelers, climate, vectors, and indigenous dengue incidence remains unclear. The role of foreign-origin cases on local dengue epidemics thus has been largely neglected by research. This study investigated the effect of both imported dengue and local meteorological factors on the occurrence of indigenous dengue in Taiwan.


RESULTS
Using logistic and Poisson regression models, we analyzed bi-weekly, laboratory-confirmed dengue cases at their onset dates of illness from 1998 to 2007 to identify correlations between indigenous dengue and imported dengue cases (in the context of local meteorological factors) across different time lags. Our results revealed that the occurrence of indigenous dengue was significantly correlated with temporally-lagged cases of imported dengue (2-14 weeks), higher temperatures (6-14 weeks), and lower relative humidity (6-20 weeks). In addition, imported and indigenous dengue cases had a significant quantitative relationship in the onset of local epidemics. However, this relationship became less significant once indigenous epidemics progressed past the initial stage.


CONCLUSIONS
These findings imply that imported dengue cases are able to initiate indigenous epidemics when appropriate weather conditions are present. Early detection and case management of imported cases through rapid diagnosis may avert large-scale epidemics of dengue/dengue hemorrhagic fever. The deployment of an early-warning surveillance system, with the capacity to integrate meteorological data, will be an invaluable tool for successful prevention and control of dengue, particularly in non-endemic countries.
Shang
Chuin-Shee
CS
Graduate Institute of Epidemiology, College of Public Health, National Taiwan University, Taipei, Taiwan.
Fang
Chi-Tai
CT
Liu
Chung-Ming
CM
Wen
Tzai-Hung
TH
Tsai
Kun-Hsien
KH
King
Chwan-Chuen
CC
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D002980:Climate; D003715:Dengue / Q000453:epidemiology*; D005260:Female; D006801:Humans; D006813:Humidity; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D013624:Taiwan / Q000453:epidemiology; D013696:Temperature; D014195:Travel; D055815:Young Adult