Abstract
Yellow fever (YF) is frequently associated with high severity and death rates in the Amazon region of Brazil. During the rainy seasons of 1998 and 1999, 23 (eight deaths) and 34 (eight deaths) human cases of YF were reported, respectively, in different geographic areas of Pará State; most cases were on Marajó Island. Patients were 1 to 46 years of age. Epidemiologic and ecological studies were conducted in Afuá and Breves on Marajó Island; captured insects yielded isolates of 4 and 11 YF strains, respectively, from Haemagogus janthinomys pooled mosquitoes. The cases on Marajó Island in 1999 resulted from lack of vaccination near the focus of the disease and intense migration, which brought many nonimmune people to areas where infected vectors were present. We hypothesize that YF virus remains in an area after an outbreak by vertical transmission among Haemagogus mosquitoes.
Highlights
Yellow fever (YF) is an important arbovirus infection of humans and sylvan primates
One is sylvatic: monkeys act as vertebrate hosts, forest canopy mosquitoes of the genera Haemagogus and Sabethes ( Haemagogus janthinomys and to a lesser extent Sabethes chloropterus) are vectors, and human infections occur as sporadic cases or as limited outbreaks [2,3,4]
We report entomologic and epidemiologic findings regarding an unusual occurrence of YF cases in an area of Pará State in 1998 and 1999
Summary
Yellow fever (YF) is an important arbovirus infection of humans and sylvan primates. Infection in humans is accompanied by high rates of illness and death. One is sylvatic: monkeys act as vertebrate hosts, forest canopy mosquitoes of the genera Haemagogus and Sabethes ( Haemagogus janthinomys and to a lesser extent Sabethes chloropterus) are vectors, and human infections occur as sporadic cases or as limited outbreaks [2,3,4]. In recent decades in South America, YF cases and outbreaks have been reported, especially in Peru, Bolivia, and Brazil, where >90% of all reported episodes of disease in the 1990s occurred [10]. In Brazil, YF occurs annually, causing sporadic cases, small outbreaks, or self-limited epidemics in the jungle or rural areas of the Amazon region (the natural focus of the disease), the Central-West region, and western regions of Maranhão and Minas Gerais states [3,4,11]. We report entomologic and epidemiologic findings regarding an unusual occurrence of YF cases in an area of Pará State in 1998 and 1999
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