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

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 Goias state, near Brasilia, 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: Goias with 64.9% (50 cases); Amazonas (1); Bahia (10); Distrito Federal (1); Mato Grosso (4); Minas Gerais (2); Para (1); Sao 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, Goias, and Sao 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 Goias state, where 40 municipalities made reports, 21 of which also diagnosed human cases. Data obtained: by the NationalInstitute of Meteorology in Brazil showed an increase in temperature and rain in December 1999 and the first 3 months of 2000 in Goias 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 mil:lion doses were used. During the last months of 1999, 16 and 11 yellow fever cases were reported in Tocantins and Goias states, respectively. It is noteworthy that the last reported autochthonous cases of sylvatic yellow fever in Sao Paulo and Bahia, both states outside the endemic/enzootic area, had occurred in 1953 and 1948, respectively. (C) 2001Wiley-Liss, Inc.