A recente outbreak of yellow fever in south of Maranhäo State, Brazil: epidemiological, clinical and entomological findings

RESUMO

An outbreak of Yellow fever virus (YF) ocorred in Maranhäo State in 1993 (Barra do Corda, Esperantinopolisand Mirador) and 1994 (Pastos Bons), where several cases were reported. In 1993 a total of 932 people was examined for YF distributedas follows 32 from Barra do Corda, 26 from Esperantinópolis and 874 from Mirador. From these, 70 cases were YF confirmed serologically (IgM capture MAC ELISA), histopathologically and/or by virus isolation. Another 4 cases diagnosed clinically and epidemiologically, brougth the total to 74 (Barra do Corda5; Esperantinópolis7 and Mirador 62). The age of patients ranged from 2 to 71 years old (mean 24)32 (43.2 percent) were female and 42 (56.8 percent) male and total lethality-rate was 17.5 percent (13/74). In Mirador ( 17,565 inhabitants), where an intesive survey was carried out, the incidence was 3,5 per 1,000 people, but in the rural YF risk area (14,695 inhabitants) the incidence was 4.2, and the mortality 16.1 percent (10/62). A total of 45.2 percent (28/62) asymptomatic infections were registered. In 1994, a total of 49 serum samples was obtained, 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 percent). In 1994, 16 strains were isolated from 1,318 Hg. janthinnomys (IR 1.34 percent) and one Sabethes chloropterus (IR1.67 percent). Our results suggest that this was the most extensive outbreak of YF in the last 20 years in Brazil