Challenges for dengue control in Brazil: overview of socioeconomic and environmental factors associated with virus circulation

Successive epidemics of dengue have been occurring in Brazil since 1986 and more than three million cases of dengue fever (DF) had already been recorded by November 2003. The introduction of the three serotypes in circulation (DEN-1, DEN- 2 and DEN-3) has always started in Rio de Janeiro. During the nineteen nineties, the incidence of dengue increased greatly as a consequence of the dissemination of Aedes aegypti in the country, beginning mainly in 1994. Between 1990 and 2000, several epidemics occurred, principally in the major urban centres of the southeast and the northeast of Brazil, where the majority of reported cases were concentrated. The first great incidence of the disease was observed in 1998, with 528,000 DF cases. Circulation of serotype 3 of the virus was detected for the first time in December 2000, in the state of Rio de Janeiro. In the period of 2001-2002, epidemics occurred in several states of the country, with more than 1.2 million of notified DF cases. Two years after the introduction of Den-3, the number of DHF cases notified achieved more than 3000, representing almost 0.3% of the total DF cases. By 1997 more than 50% of the 5543 counties were infested by Ae. aegypti. Unplanned urban growth, with deficiencies in water supply and urban cleaning, has increased the opportunities for the mosquito reproductio