An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994: Epidemiologic and entomologic findings

Pedro F C Vasconcelos, Sueli G. Rodrigues, Nicolas Degallier, Mario A P Moraes, Jorge F S Travassos Da Rosa, Elizabeth S. Travassos Da Rosa, Bernard Mondet, Vera L R S Barros, Amelia P A Travassos Da Rosa

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Abstract

Yellow fever virus transmission was very active in Maranhao State in Brazil in 1993 and 1994. An investigation was carried out to evaluate the magnitude of the epidemic. In 1993, a total of 932 people was examined for yellow fever from Maranhao: 70 were positive serologically, histopathologically, and/or by virus isolation, and another four cases were diagnosed clinically and epidemiologically. In Mirador (17,565 inhabitants), the incidence was 3.5 per 1,000 people (case fatality rate [number of deaths/number of cases diagnosed] = 16.4%), while in a rural yellow fever risk area (14,659 inhabitants), the incidence was 4.2 and the case-fatality rate was 16.1% (10 of 62). A total of 45.2% (28 of 62) asymptomatic infections were registered. In 1994, 49 serum samples were obtained and 16 cases were confirmed (two by virus isolation, two by seroconversion, and 12 by serology). No fatal cases were reported. In 1993, 936 potential yellow fever vectors were captured in Mirador and a single strain was isolated from a pool of Haemagogus janthinomys (infection rate = 0.16%). In 1994, 16 strains were isolated from 1,318 Hg. janthinomys (infection rate = 1.34%) and one Sabethes chloropterus (infection rate = 1.67%). Our results suggest that this was the most extensive outbreak of yellow fever in the last 20 years in Brazil. It is also clear that the lack of vaccination was the principal reason for the epidemic, which occurred between April and June, during the rainy season, a period in which the mosquito population in the forest increases.

Original languageEnglish (US)
Pages (from-to)132-137
Number of pages6
JournalAmerican Journal of Tropical Medicine and Hygiene
Volume57
Issue number2
StatePublished - Aug 1997
Externally publishedYes

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Yellow Fever
Brazil
Infection
Yellow fever virus
Viruses
Asymptomatic Infections
Mortality
Incidence
Serology
Culicidae
Disease Outbreaks
Vaccination
Serum
Population

ASJC Scopus subject areas

  • Parasitology
  • Infectious Diseases

Cite this

Vasconcelos, P. F. C., Rodrigues, S. G., Degallier, N., Moraes, M. A. P., Travassos Da Rosa, J. F. S., Travassos Da Rosa, E. S., ... Travassos Da Rosa, A. P. A. (1997). An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994: Epidemiologic and entomologic findings. American Journal of Tropical Medicine and Hygiene, 57(2), 132-137.

An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994 : Epidemiologic and entomologic findings. / Vasconcelos, Pedro F C; Rodrigues, Sueli G.; Degallier, Nicolas; Moraes, Mario A P; Travassos Da Rosa, Jorge F S; Travassos Da Rosa, Elizabeth S.; Mondet, Bernard; Barros, Vera L R S; Travassos Da Rosa, Amelia P A.

In: American Journal of Tropical Medicine and Hygiene, Vol. 57, No. 2, 08.1997, p. 132-137.

Research output: Contribution to journalArticle

Vasconcelos, PFC, Rodrigues, SG, Degallier, N, Moraes, MAP, Travassos Da Rosa, JFS, Travassos Da Rosa, ES, Mondet, B, Barros, VLRS & Travassos Da Rosa, APA 1997, 'An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994: Epidemiologic and entomologic findings', American Journal of Tropical Medicine and Hygiene, vol. 57, no. 2, pp. 132-137.
Vasconcelos PFC, Rodrigues SG, Degallier N, Moraes MAP, Travassos Da Rosa JFS, Travassos Da Rosa ES et al. An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994: Epidemiologic and entomologic findings. American Journal of Tropical Medicine and Hygiene. 1997 Aug;57(2):132-137.
Vasconcelos, Pedro F C ; Rodrigues, Sueli G. ; Degallier, Nicolas ; Moraes, Mario A P ; Travassos Da Rosa, Jorge F S ; Travassos Da Rosa, Elizabeth S. ; Mondet, Bernard ; Barros, Vera L R S ; Travassos Da Rosa, Amelia P A. / An epidemic of sylvatic yellow fever in the southeast region of Maranhao State, Brazil, 1993-1994 : Epidemiologic and entomologic findings. In: American Journal of Tropical Medicine and Hygiene. 1997 ; Vol. 57, No. 2. pp. 132-137.
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abstract = "Yellow fever virus transmission was very active in Maranhao State in Brazil in 1993 and 1994. An investigation was carried out to evaluate the magnitude of the epidemic. In 1993, a total of 932 people was examined for yellow fever from Maranhao: 70 were positive serologically, histopathologically, and/or by virus isolation, and another four cases were diagnosed clinically and epidemiologically. In Mirador (17,565 inhabitants), the incidence was 3.5 per 1,000 people (case fatality rate [number of deaths/number of cases diagnosed] = 16.4{\%}), while in a rural yellow fever risk area (14,659 inhabitants), the incidence was 4.2 and the case-fatality rate was 16.1{\%} (10 of 62). A total of 45.2{\%} (28 of 62) asymptomatic infections were registered. In 1994, 49 serum samples were obtained and 16 cases were confirmed (two by virus isolation, two by seroconversion, and 12 by serology). No fatal cases were reported. In 1993, 936 potential yellow fever vectors were captured in Mirador and a single strain was isolated from a pool of Haemagogus janthinomys (infection rate = 0.16{\%}). In 1994, 16 strains were isolated from 1,318 Hg. janthinomys (infection rate = 1.34{\%}) and one Sabethes chloropterus (infection rate = 1.67{\%}). Our results suggest that this was the most extensive outbreak of yellow fever in the last 20 years in Brazil. It is also clear that the lack of vaccination was the principal reason for the epidemic, which occurred between April and June, during the rainy season, a period in which the mosquito population in the forest increases.",
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AU - Moraes, Mario A P

AU - Travassos Da Rosa, Jorge F S

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