Epidemic of jungle yellow fever in Brazil, 2000: Implications of climatic alterations in disease spread

Abstract

Seventy-seven human cases of sylvatic yellow fever were reported in Brazil during the period January-June 2000. The first cases were reported 1 week after New Year's day and originated at Chapada dos Veadeiros, a tourist canyon site in Goiás state, near Brasília, the Brazilian capital. The laboratory procedures used for diagnoses included serology with an IgM capture assay and plaque reduction neutralization test, virus isolation in suckling mice and C6/36 cells, and immunohistochemistry. All cases were diagnosed by at least two different laboratory procedures, with the exception of the first three fatal cases, which were diagnosed on the basis of clinical and epidemiological information. The cases were reported in eight Brazilian states as follows: Goiás with 64.9% (50 cases); Amazonas (1); Bahia (10); Distrito Federal (1); Mato Grosso (4); Minas Gerais (2); Pará (1); São Paulo (2); and Tocantins (6). Patient ages were within the following ranges: 13-74 years old (mean 34.3), 64 (84.4%) were male, especially agricultural workers (n = 30), but tourists (n = 11), carpenters (n = 4), fishermen (n = 4), students (n = 3), truck drivers (n = 3), and other people (n = 22) were also sickened. The case fatality rate was 50.6% (39/77). In Bahia state, a serologic survey that was carried out has suggested a symptomatic/asymptomatic coefficient of 1:4. Field studies developed in Distrito Federal, Goiás, and São Paulo states showed that Haemagogus janthinomys was the mosquito species associated with the transmission. A single strain was also obtained from Aedes scapularis in Bahia. Epizootic occurrence (monkey mortality) was observed in 49 municipalities mainly in Goiás state, where 40 municipalities made reports, 21 of which also diagnosed human cases. Data obtained by the National Institute of Meteorology in Brazil showed an increase in temperature and rain in December 1999 and the first 3 months of 2000 in Goiás and surrounding states, which perhaps has contributed to the intense and widespread transmission of the yellow fever virus. The relatively small number of cases probably reflects the extensive use of yellow fever 17D-vaccine during the last 3 years, in which about 45 million doses were used. During the last months of 1999, 16 and 11 yellow fever cases were reported in Tocantins and Goiás states, respectively. It is noteworthy that the last reported autochthonous cases of sylvatic yellow fever in São Paulo and Bahia, both states outside the endemic/enzootic area, had occurred in 1953 and 1948, respectively.

Yellow fever in Brazil: thoughts and hypotheses on the emergence in previously free areas

“…15 A 10-year survey of offi cial data recorded between 1991 and 2000 by the Instituto Nacional de Meteorologia (INMET -National Institute of Meteorology) showed that temperatures increased and rainfall index was much higher in 2000 than the average for 1990 to 1999. This suggests that increased rainfall favored mosquito proliferation and high temperatures promoted viral spread and transmission.…”

“…12 Indeed, molecular analysis showed that yellow fever virus isolates from Marajó island in the Northern state of Pará 16 were identical to yellow fever viral strains found in Goiás and Bahia. 15 Since these two areas where infection probably occurred were more than 2,000 km apart ( Figure), viral spread through monkeys is not possible, and only viremic humans with oligosymptomatic or even asymptomatic infections could have carried these yellow fever virus strains. 20 Another way is illegal traffi c of wild animals.…”

Avaliação do impacto da epizootia de Febre Amarela sobre as populações de primatas não humanos nas unidades de conservação do Rio Grande do Sul, Brasil

“…Há relatos de mortalidades em primatas devido à febre amarela, incluindo aquelas que afetaram bugios, mas muitas vezes o número de animais afetados é incerto (COLLIAS; SOUTHWICK, 1952;ELTON, 1952;VARGAS-MENDEZ;ELTON, 1953;ANDERSON;DOWNS, 1965;BEJARANO, 1979;SOPER, 1979;MENDES, 1989;DÉGALLIER et al, 1992a;1992b;VASCONCELOS et al, 2001;COLOMBIA, 2002;BRYANT et al, 2003;SALLIS et al, 2003a;RIFAKIS et al, 2006;AGOSTINI et al, 2008;HOLZMANN et al, 2010). No mais recente surto, a partir dos primeiros registros em Misiones, Argentina (HOLZMANN et al, 2010) a propagação do VFA no Rio Grande do Sul tomou sentido oeste-leste, com a detecção de FA em primatas avançando pelo Estado ao ritmo de 100km/ mês (ALMEIDA et al, 2012).…”

“…No Brasil, a FA tem caráter sazonal, ocorrendo mais frequentemente entre os meses de dezembro a abril , quando fatores ambientais (tais como maior precipitação e temperatura) propiciam o aumento da abundância dos vetores (VASCONCELOS et al 2001;. O VFA se mantém por meio de dois ciclos básicos: o urbano e o silvestre.…”

Detección por reacción en cadena de la polimerasa de transcriptasa inversa del virus de la fiebre amarilla en monos silvestres: una herramienta sensible para la vigilancia epidemiológica

“…Teniendo en cuenta las condiciones epidemiológicas de la enfermedad en áreas endémicas y como una estrategia de control para evitar la reurbanización de la fiebre amarilla en Colombia, la vigilancia en zonas de alto riesgo debe incluir no sólo la implementación de sitios centinela que permitan determinar la presencia de casos humanos (9,21,27,28) sino, además, un seguimiento a epizootias que representan riesgo de infección en área selvática (16,19). Así, la detección precoz del virus de la fiebre amarilla en tejido proveniente de monos muertos, además de ser una clara evidencia de la actividad selvática viral, constituye un sistema de alerta temprana que indica la necesidad de intensificar medidas de control, como vacunación en las áreas cercanas, estudio de vectores tanto selváticos como urbanos y búsqueda activa de casos que puedan desencadenar un brote o epidemia.…”