The study in Scientific Reports was able to retrace the spread of the yellow fever pathogen from the state of Pará by analysing tissue samples from dead howler monkeys. The current ongoing yellow fever epidemic is the worst in forty years. Using a molecular study of yellow fever viruses found in dead monkeys, including howler monkeys, and in mosquitoes, the research group discovered that the origin of the strain behind the current epidemic originated in Pará State in North Brazil in 1980. The chain of events they identified is as follows: “More than 90% of the dead monkeys are believed to be Alouatta guariba. The species is extremely susceptible to yellow fever,” said Ester Sabino, Director of IMT-USP. Speaking about the deaths of howler monkeys from yellow fever in Horto Florestal, a nature reserve in the north of São Paulo City in late 2017, Mariana Sequetin Cunha, the lead of this investigation and a researcher from IAL’s Vector-Borne Disease Group, added: “Troops of more than 80 monkeys were entirely destroyed.” According to the researchers, the results of the forthcoming studies may enable the determination of whether or not the current epidemic in São Paulo State is on the wane or whether there could be fresh outbreaks due to the virus still spreading in monkeys despite mass vaccination.
An outbreak of yellow fever in Brazil has been traced to howler monkeys by scientists from the Adolfo Lutz Institute and the University of Sao Paulo. Researchers conducted a molecular study of the virus in mosquitoes and in dead monkeys, pinpointing the origin of the outbreak to northern Brazil's the Brazilian Ministry of Health state in approximately 1980. In 2017, Para reported outbreaks of yellow fever in areas believed to be low-risk. A year later, a Dutch tourist in Sao Paulo contracted the virus. There have since been reports of tourists contracting the disease in the Rio de Janeiro state.