A survey was conducted in 6 internal and external districts of Hanoi city which produced the following results: The rate of Ae. aegypti collected was much lower than that of Ae. albopictus (26.00 percent and 74.00 percent respectively). The number of houses having Aedes occupied 30.05 percent
The general mosquito density was 0.70 (mosquito per house). The area of Hoang Mai, Thanh Tri and Soc Son had a quite high density (1.13 to 1.20). The density of Ae. aegypti was 0.42
and Ae. albopictus in Hanoi during the study period had a low density of 0.23 mosquito per house. These indices were twice as high as the risk stipulated by the Ministry of Health in 2006. The number of houses in the study sites having Aedes spp larval accounted for 50.00 percent on average, while Thanh Xuan got the lowest percentage of 96.32 and Hoang Mai got the highest of 68.13 percent. The average Breteau index in Hanoi at the time of study was 109.32, higher than the limit set by the Ministry of Health in 2006 (BI 50) with the highest in Phuc Tho (259.38) and the lowest in Thanh Xuan (6.32).