The retrospective study describes some epidemiological characteristics of dengue hemorrhagic fever (DHF) in Hanoi from 2006 to 20 II, results show that: the prevalence per 100,000 population increased by 7-10 times compared with previous period
DHF cases were recorded in 29/29 districts and towns, but mainly (80 percent -90 percent) in 10 urban and 02 rural districts (Thanh Tri, Tu Liem) where the population density is high and the urbanization takes place rapidly. Patients appear all around the year, the incidence increased from June and peaked in September and October. Pupils, students and workers from other provinces accounted for 50 percent -60 percent of the total of patients. Most DHF cases were in mild form (grade 1 and II), only a few serious cases. Percentage ofpositive MAC-ELISA test was not high (10 percent 30 percent), the proportion of specimens isolated the virus was higher (from 30 percent -60 percent) with the presence of 4 dengue virus types, but mainly Dengue type 1 (D1) and Dengue type 2 (D2)
vectors included both types - Ae. aegypti and Ae. albopictus.