Risk factors for infection during a severe dengue outbreak in El Salvador in 2000.

In 2000, El Salvador experienced a large dengue-2 virus epidemic with many severe cases. A seroepidemiologic survey was conducted in 106 randomly selected households (501 residents) in an affected community (Las Pampitas). The frequency of recent infection, documented by the presence of IgM antibodies or high-titer IgG antibodies to dengue virus, was estimated to be 9.8% (95% confidence interval [CI] = 5.8-13.7), of which at least 44% were secondary infections. The number of containers positive for Aedes mosquito larvae or pupae per 100 premises (Breteau Index) was 62 and the frequency of positive premises (House Index) was 36%; 33% (35 of 106) of the informants reported having taken action against mosquito larval habitats and 82% (87 of 106) reported having taken actions against adult mosquitoes. Recent infection was associated with the presence in the home environment of mosquito infested discarded cans (odds ratio [OR] = 4.30, 95% CI = 2.54-7.28), infested discarded plastic containers (OR = 3.98, 95% CI = 1.05-15.05), and discarded tire casings (OR = 2.57, 95% CI = 1.09-6.04). The population attributable fractions associated with these factors were 4%, 13%, and 31%, respectively. Our data suggest that targeted community cleanup campaigns, particularly those directed at discarded tires and solid waste, are likely to have the greatest impact on reducing the risk of dengue infection.