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Yellow fever outbreaks in nonhuman primates pose ‘considerable risk’ to humans
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A yellow fever outbreak driven by epizootic transmission in Brazil highlights the importance of monitoring mosquito populations and nonhuman primate deaths when assessing the risk for infection among humans, according to findings published in Annals of Internal Medicine.
In the Americas, yellow fever virus (YFV) is known to circulate in nonhuman primates (NHPs), according to Igor Adolfo Dexheimer Paploski, DVM, MSc, DPH, epidemiologist at the Federal University of Bahia, Instituto Gonçalo Moniz and Oswaldo Cruz Foundation, and colleagues. Zoonotic spillover to humans is rare; however, concerns about reemergence of the virus recently increased with the rapid reappearance and spread of Aedes aegypti mosquitoes — a vector for yellow fever in urban settings.
“To date, urban Aedes mosquitoes have not been associated with YFV transmission to humans in Brazil,” the researchers wrote. “However, cases of YFV in NHPs in densely urbanized areas pose a considerable risk for resurgence of A. aegypti-mediated YFV transmission to humans.”
Signs of the recent yellow fever outbreak in Brazil first began in November 2016, when deaths caused by YFV were identified among NHPs, according to the researchers. Human cases began to emerge a month later. By the end of May, the outbreak had spread to more than 130 municipalities in nine Brazilian states. Overall, 3,250 suspected and 792 laboratory-confirmed infections as well as 435 deaths were reported among humans. In addition, there were 3,850 suspected and 642 confirmed-laboratory confirmed deaths among NHPs.
Paploski and colleagues recently assessed the risk for yellow fever transmission among humans in Salvador — an area that had not been considered to have a high risk for transmission — during the outbreak. The researchers identified 205 NHPs with suspected yellow fever infection throughout the city, with clusters around a city park and recreational area. They tested 435 adult mosquitoes captured in 26 sites between April 10, 2017, and June 7, 2017, to determine their role in transmission. None of the mosquitoes tested positive for YFV.
“Continuous entomologic and veterinary surveillance of mosquitoes and NHP deaths, accompanied by laboratory testing for YFV, is the cornerstone of assessing the risk that this virus will establish an urban transmission cycle,” the researchers concluded. “In parallel, scaling up vaccination coverage is critical to prevent additional human cases of this disease.” – by Stephanie Viguers
Disclosures: The authors report no relevant financial disclosures.
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