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Monday, March 18, 2019

Last outbreak yellow fever in Brazil originated in primates, according to study

The largest outbreak of yellow fever in Brazil in recent decades, with more than 2,000 confirmed cases and 676 deaths between December 2016 and March 2018, originated in non-human primates in forested areas and then spread to people, according to a report. study published today in the journal Science.
To understand how this outbreak occurred, the team led by Nuno Faría, of the University of Oxford, analyzed epidemiological, spatial and genomic data of the region, and compared a time series of confirmed cases in people and non-human primates.
The researchers found that human cases lagged behind those of primates in four days and found that the risk of yellow fever was higher for people who lived or worked in wooded areas, where mosquitoes that usually bite primates can bite and transmit the virus to humans.
The results were "surprising," said Faría, who explained that in areas close to the origin of the outbreak, 85% of the cases were in men, more likely to travel through remote areas of the jungle than women.
The researchers also sequenced 62 yellow fever genomes of infected humans and primates from the most affected Brazilian states, comparing these genomes with those previously published.
The data suggest that the 2017 outbreak was probably caused by a strain introduced from an endemic area, possibly in the northern or central-eastern region of Brazil, rather than by the resurgence of a lineage that had persisted in the Minas Gerais area. , as other reports had indicated.
Although the epidemic was probably initiated in primates, the spread of the virus "appears to have been aided by human activity", for example, by the transport of infected mosquitoes in vehicles or by the illegal trade in primates, according to the authors.
Although there is an effective vaccine against yellow fever, the virus causes between 29,000 and 60,000 deaths annually in South America and Africa, the two regions most affected by this type of disease. 

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