Zika virus has been discovered in monkeys for the first time since the widespread outbreak in Brazil, raising concerns there is a “natural reservoir” of the disease.
Zika was first discovered in monkeys in Uganda in 1947, but has since spread predominantly among humans via mosquitoes. However, the detection of Zika in dead primates in Brazil raises concerns that the disease has a wild cycle similar to yellow fever.
If confirmed, this would make combating Zika much more difficult than previously assumed. Most of the major pandemics of the last 100 years began in animals, including the Spanish flu which jumped from birds to humans, and HIV which came from chimps.
“The discovery shows the potential exists for Zika to establish a sylvatic transmission cycle [involving wild animals] in Brazil, as already occurs in the case of yellow fever,” said Prof Maurício Lacerda Nogueira, lead researcher of the report and professor at São José do Rio Preto Medical School.
“If the wild cycle is confirmed, it completely changes the epidemiology of Zika because it means there's a natural reservoir from which the virus can re-infect the human population much more frequently."
The virus was detected in monkeys near São José do Rio Preto and Belo Horizonte in southern Brazil, according to the study published in Scientific Reports on Tuesday. Locals had shot or beaten the monkeys as they had believed they carried yellow fever.
It is the first discovery of Zika in a wild population since the outbreak in 2015 and 2016, which swept throughout Brazil and Latin America. While the virus usually produces fairly mild symptoms, the epidemic has been linked to a spate of neurological defects among babies born to mothers infected with the disease.
Experts say that the existence of Zika in monkeys is a "game changer".
“Our observations will have important implications in our understanding of the ecology and transmission of Zika in the Americas,” said Prof Nikos Vasilakis, lead author of the study and vice chair for research at the University of Texas’ Centre for Tropical Diseases.
“Although this is among the first steps in the establishment an enzootic transmission cycle among New World nonhuman primates and arboreal mosquitoes, the implications are enormous, because it is impossible to eradicate this transmission cycle."
“It's a game changer and policy makers, public health officials, as well as vaccine developers, should take notice”, he added.
The report, funded by the São Paulo Research Foundation, said additional research was needed to establish the extent of Zika prevalence within Brazil’s monkey population.
Zika is not is confined to the Americas as this map shows. There is currently a serious outbreak in India, much of Africa presents a risk as does much of the Pacific.
global health security correspondent