An overview of arbovirology in Brazil and neighbouring countries

An outbreak of Yellow fever virus (YF) occurred in Maranhao State in 1993 (Barra do Corda, Esperantinopolis and Mirador) and 1994 (Pastos Bons), where several cases were reported. In 1993 a total of 932 people were examined for YF distributed as follows : 32 from Barra do Corda, 26 from Esperantinopolis and 874 from Mirador. From these, 70 cases were YF confirmed serologically (IgM capture MAC ELISA), histophathologically and/or by virus isolation. Another 4 cases diagnosed clinically and epidemiologically, brought the total to 74 (Barra do Corda : 5, Esperantinopolis : 7, and Mirador : 62). The age of the patients ranged from 2 to 71 years old (mean : 24) : 32 (43.2%) were female and 42 (56.8%) male and the total lethality-rate was 17.5% (13/74). In Mirador (17,565 inhabitants), where an intensive survey was carried out, the incidence was 3.5 per 1,000 people, but in the rural YF risk area (14,659 inhabitants) the incidence was 4.2, and the mortality 16.1% (10/62). A total of 45.2% (28/62) asymptomatic infections were registered. In 1994, a total of 49 serum samples were obtained from Pastos Bons. Of these, 16 cases, 8 females and 8 males, were YF confirmed as follows : 2 by virus isolation, 2 by seroconversion and 12 by serology. On the other hand, no fatal cases were reported in Pastos Bons. In 1993, 936 potential YF vectors were captured in Mirador and a single strain was isolated from a pool of #Haemagogus janthinomys$ (infection rate (IR) : 0.16%). In 1994, 16 strains were isolated from 1,318 #Hg. janthinomys$ (IR : 1.34%) and one #Sabethes chloropterus$ (IR : 1.67%). Our results suggest that this was the most extensive outbreak of YF in the last 20 years in Brazil. (Résumé d'auteur)