A quick reminder: there’s a band of feral monkeys running wild in Central Florida that carries a type of herpes lethal to humans. The mischievous simians—who are not shy around people—can transmit deadly disease with just a scratch, nip, or fling of poo.

Last year, experts warned that the rhesus macaques are a public health threat. It now seems that the monkey business is likely to get worse, with a wildlife expert revealing that their population is set to double in the next few years.

“It’s going to be a problem… Continual growth of that population is going to occur without intervention,” Steve Johnson told Florida ABC-affiliate WFTV in a report published January 3. Johnson is a professor and wildlife expert at the University of Florida and part of a team of researchers that has followed the monkeys for years.

Early last year, Johnson and colleagues published a study estimating that about 25 percent of Florida’s population of free-wheeling monkeys carries the deadly virus, known as macacine herpesvirus 1 (McHV-1), herpes B, or monkey B virus. The study appeared in the February issue of Emerging Infectious Diseases.

The monkey’s herpes affects them much like human herpes (HSV-1 and HSV-2) affects us. The virus infects nerves and can go dormant until the immune system is stressed or weakened, at which point the virus can erupt, typically around the mouth or genitals.

But in humans, McHV-1 can cause a flu-like illness that can progress to neurological problems, such as double vision and paralysis. At that point, an infected person is likely to die of the infection.

So far, researchers have only documented 50 cases of McHV-1 spreading to humans, all of which came from captive, not wild, monkeys. But with a feisty population of monkeys running amok around Central Florida, researchers say the potential for the virus to jump from the wild to humans is real—particularly with more monkeys around.

Currently, Johnson and colleagues estimate that there are about 200 monkeys in Florida’s Silver Spring State Park. “By the year 2022, there are probably going to be around 400 animals,” Johnson said.

The population got its start during the 1930s and 1940s when the captain of a glass-bottom boat released a handful of macaques on an island in Florida’s Silver River to amuse tourists. The monkeys, which are excellent swimmers, established in the surrounding Silver Spring State Park and nearby Ocala National Forest.