Though at least 25 percent of the population carries the virus — which causes mild disease in macaques, but can be deadly to humans — fewer were actually infectious. The virus lies dormant in nerves in between flare-ups, similar to cold sores in humans. Between 4 and 14 percent of the monkeys released the virus in their spit during their fall breeding season, researchers report in the journal Emerging Infectious Diseases. And the wild monkeys’ poop turned out to be pristine — at least, as far as herpes B was concerned.
“The headlines have already taken off about this, but there’s really a lot we still don’t know about herpes B in wild monkeys,” says study author Samantha Wisely, a wildlife biologist at the University of Florida. The virus is what she calls low-risk, but high-consequence — like rabies, she says. “There’s really a low risk of you getting it, but if you get it, there are going to be very high consequences.”
Florida’s feral rhesus macaque monkeys are native to southern and eastern Asia, and are particularly adorable and effective invaders. They got to the state the usual way — by hitching a ride with misguided humans who thought the cute little creatures could draw tourists. Between 1930 and 1950, a dozen rhesus macaques were introduced to central Florida’s Silver Springs State Park, where they multiplied. By 2012, 1,000 rhesus macaques had been trapped and removed before public outcry stopped the control effort. (People sure love furry, feral, ecosystem-endangering mammals.) At last count in 2015, some 175 macaques were living in Silver Springs State Park.
Macaques can become a nuisance in new environments. They destroy crops, contaminate water, and chow down on native birds’ eggs and chicks. They also can carry herpes B, which usually doesn’t do anything to the monkeys, but sometimes causes cold sores, mouth ulcers, and eye irritation. After the initial infection, the virus hides out in the animal’s nerves, flaring up only when the monkey gets sick or stressed. When it does, the monkey can become contagious, secreting the virus in its spit, pee, or poop. That’s how the virus can spread to people. In humans, herpes B causes a devastating brain disease that the CDC says is deadly about 70 percent of the time — especially without treatment.