Environmental factors of households in five districts of Kerala affected by the epidemic of chikungunya fever in 2007.

ABSTRACT

Background. Two epidemics of chikungunya fever were reported from Kerala in 2006 and 2007. We aimed to investigate the environmental factors of households affected by chikungunya fever and to estimate the proportion of population that suffered from the disease during the epidemic in 2007. Methods. A cross-sectional survey was conducted in the 5 heavily affected districts of Kerala during October–November 2007. The 2-stage sampling technique was used to collect data from 10 clusters, each having 18 houses from every district, by interviewing the subjects using a structured questionnaire. The sample size was 900. Results. The proportion of the population affected by chikungunya fever was 57.1% (95% CI 52.8%–61.4%). There was a significant association between location of houses and disease status. Houses located near a public conveyance facility (within 250 m) were relatively protected from the disease (OR 0.19 [0.06–0.60]). About 69% of the households perceived mosquito infestation as a problem and 46.6% used fumes to avoid mosquitoes. More than 42% of households were not using any anti-mosquito measures at the time of the survey. Stored drinking water was the most common potential breeding source in the houses (23.5%). Households which did not store water inside were protected from the disease (OR 0.22 [0.08–0.65]). Conclusion. The study indicated the persistence of favourable domestic and environmental factors after the epidemic, reflecting the necessity to strengthen anti-mosquito campaigns.