The last outbreak of yellow fever in Brazil originated in primates, according to a study



Washington – 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 wooded areas and then spread to humans, according to A study published today in the journal Science.

To understand how this outbreak occurred, the Nuno Faría team at the University of Oxford analyzed epidemiological, spatial and genomic data from the region and compared a time series of confirmed cases in humans and non-human primates.

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 living or working in wooded areas, where mosquitoes that usually bite primates can bite and transfer 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 often by remote areas of the jungle than women.

The researchers also took 62 yellow fevers from infected people and primates from the most affected Brazilian states by comparing these with the previously published ones.

The data suggest that the outbreak in 2017 was probably caused by a strain introduced from an endemic region, possibly in the northern or central-eastern region of Brazil, rather than by the revival of a lineage that had existed in the area of ​​Minas Gerais. , as other reports had indicated.

Although the epidemic was probably initiated in primates, the spread of the virus seems to have been helped by human activities, for example by transporting infected mosquitoes in vehicles or by carrying out illegal trafficking 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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