With cluster as the unit of analysis , serological evidence from intervention sites showed a lower risk of infection with dengue virus in children ( relative risk reduction 29.5 % , 95 % confidence interval 3.8 % to 55.3 % ) , fewer reports of dengue illness ( 24.7 % , 1.8 % to 51.2 % ) , fewer houses with larvae or pupae among houses visited ( house index ) ( 44.1 % , 13.6 % to 74.7 % ) , fewer containers with larvae or pupae among containers examined ( container index ) ( 36.7 % , 24.5 % to 44.8 % ) , fewer containers with larvae or pupae among houses visited ( Breteau index ) ( 35.1 % , 16.7 % to 55.5 % ) , and fewer pupae per person ( 51.7 % , 36.2 % to 76.1 % ) .