There’s a Growing Population of Wild Monkeys With a Deadly Herpes Virus in Florida

The risk that humans may contract the deadly herpes virus is low, but the number of monkeys with the virus is set to explode, increasing risk of contact.
A rhesus Macaque
A rhesus Macaque. Image: Wikimedia Commons

Experts say that a population of rhesus macaques infected with a deadly herpes virus in central Florida is on the verge of doubling, which increases the risk that the virus will be transmitted to humans.

According to local ABC-affiliate WFTV, the approximately 200 rhesus macaques that roam Silver Springs State Park were brought to Florida in the 1930s and were originally contained on an island within the park. Over the past 80 years, however, the monkeys have spread throughout central Florida and according to one expert, the population is set to double in the coming years.


“By the year 2022, there are probably going to be around 400 animals,” Steve Johnson, a wildlife ecologist at the University of Florida who has spent years studying the monkeys, told WFTV. “Continual growth of that population is going to occur without intervention. It’s going to be a problem.”

According to recent research by Johnson, the rhesus macaque population first reached 400 individuals in the mid-1980s and continued to balloon from there. From 1984 to 2012, over 1,000 monkeys were removed from the state park and sold to biomedical research companies as part of an effort to "reduce macaque density and related interactions with people and negative ecosystem effects."

According to Johnson and his colleagues, this trap and removal program was halted in Florida in 2012 following years of negative public sentiment about the program. Over the last six years, no population management programs have been implemented in Silver Springs, which has allowed the rhesus macaque population to quickly rebound.

Last February, the Center for Disease Control published research on the Florida macaque population, which found that roughly 25 percent of the monkeys carried macacine herpesvirus 1 (McHV-1), a disease that can be fatal in humans. The report noted that the McHV-1 virus can be transmitted from the monkeys to humans and concluded that wildlife management plans should be put in place to limit human exposure to the virus.

“Outside of the laboratory setting, little is known about the risk of transmission or the incidence of human disease resulting from McHV-1 exposure,” researchers wrote in the CDC report. “No human deaths have been reported from contracting McHV-1 from free-ranging macaques, suggesting the risk for transmission from these animals is low; however…investigations in humans are lacking.”

Although there were no deaths attributed to herpes transmissions from the monkeys, there have been a number of documented cases of the monkeys biting or scratching visitors to Silver Springs. As the CDC found in its research, the herpes virus carried by the monkeys can be shed through their saliva, urine and feces, which makes such encounters even more dangerous.

Following the CDC report, Florida made it illegal to feed the macaques in order to discourage these sorts of encounters. Yet if nothing is done to keep the macaque population in check, their increasing numbers could lead to more human encounters anyway and increase the risk that the herpes virus is transmitted to humans.