Reemergence of yellow fever: detection of transmission in the State of S？o Paulo, Brazil, 2008

introduction: following yellow fever virus (yfv) isolation in monkeys from the s？o josé do rio preto region and two fatal human autochthonous cases from the ribeir？o preto region, state of s？o paulo, brazil, two expeditions for entomological research and eco-epidemiological evaluation were conducted. methods: a total of 577 samples from humans, 108 from monkeys and 3,049 mosquitoes were analyzed by one or more methods: virus isolation, elisa-igm, rt-pcr, histopathology and immunohistochemical. results: of the 577 human samples, 531 were tested by elisa-igm, with 3 positives, and 235 were inoculated into mice and 199 in cell culture, resulting in one virus isolation. one sample was positive by histopathology and immunohistochemical. using rt-pcr, 25 samples were processed with 4 positive reactions. a total of 108 specimens of monkeys were examined, 108 were inoculated into mice and 45 in cell culture. four virus strains were isolated from alouattacaraya. a total of 931 mosquitoes were captured in sao jose do rio preto and 2,118 in ribeir？o preto and separated into batches. a single isolation of yfv was derived from a batch of 9 mosquitoes psorophoraferox, collected in urupês, ribeir？o preto region. a serological survey was conducted with 128 samples from the municipalities of s？o carlos, rinc？o and ribeir？o preto and 10 samples from contacts of patients from ribeir？o preto. all samples were negative by elisa-igm for yfv. conclusions: the results confirm the circulation of yellow fever, even though sporadic, in the sao paulo state and reinforce the importance of vaccination against yellow fever in areas considered at risk.