Epidemiology and control of chikungunya fever in Singapore.

OBJECTIVES: We conducted an epidemiological review of the chikungunya fever situation in Singapore and described the measures taken to prevent the chikungunya virus from becoming entrenched in the tropical city-state. METHODS: All laboratory-confirmed cases and outbreak investigation reports maintained by the Communicable Diseases Division, Ministry of Health, and Aedes mosquito surveillance data obtained by the National Environment Agency during the period 2006 and 2009 were reviewed and analysed. RESULTS: Sporadic cases were imported into Singapore until the first local transmission occurred in an urban area where Aedes aegypti was the predominant vector. Subsequent introduction of a mutant viral strain (A226V) in early 2008 resulted in the rapid spread to suburban and rural areas where Aedes albopictus was the primary vector. 1072 cases including 812 (75.7%) indigenous cases were reported. The main sources of importation were India and Malaysia. Foreign contract workers were identified as high-risk for indigenous infections. CONCLUSIONS: The disease was successfully brought under control through aggressive vector control measures directed at A. albopictus. Although the incidence has sharply declined since January 2009, a high degree of vigilance is maintained to prevent a recurrence of epidemic transmission which can occur even with a well-established nationwide mosquito control programme.