CLAY COUNTY, Fla. -

Clay County issued a warning Wednesday about a rare virus that can be deadly in both horses and humans.

The Clay County Health Department issued an advisory warning residents and horse owners about an increase in eastern equine encephalitis, a mosquito-borne disease that officials said several horses in Clay County have tested positive for.  

Health officials said the horses that tested positive for EEE increase the risk of transmission to humans as well. News4Jax spoke to a veterinarian and health officials in Clay County about how to protect people and horses from the disease.  

Equine veterinarian Peggy Fuller told News4Jax Wednesday that the EEE virus comes on strong and fast and kills most horses that are not vaccinated against it. Fuller said she’s grateful for the advisory the Clay County Health Department put out to the public Wednesday. 

"Well, it’s very dangerous," said Fuller. "It’s fatal in most cases with horses. Fortunately, it can be prevented with vaccinations.” 

Three horses in Clay County tested positive for EEE. 

"I’m glad that there is an advisory because this is something that is fairly preventable if you vaccinate on a routine basis,” said Fuller. 

The Clay County Health department is also warning humans about the disease, saying that EEE can be transferred to humans by mosquitoes.    

“We want to make sure that people are wearing bug spray, draining and covering any standing water that’s in their yard or any place in their immediate area, that they cover themselves when they go out, especially in the early evening because that’s when the mosquitoes are most prevalent," said Clay County Health Department’s Winifred Holland. 

In humans, symptoms of EEE include a high fever, muscle pain, headaches and seizures. The symptoms can occur anywhere from three to 10 days after the bite from an infected mosquito. 

"It causes inflammation around the brain and the horses get uncoordinated, depressed, they run fevers and within a 24 hour period you’ll start to see the signs and they can become recumbent and can actually seizure within a very short period of time," said Fuller. 

Fuller urges horse owners to have their horses vaccinated every six months as a precaution. She told News4Jax the vaccinations are 90 percent effective. Horse owners can also give their horse a booster during peak mosquito season months. The vaccines only cost about $15 to $20. 

Humans should use mosquito spray with at least 30 percent deet and wear long sleeves when you’re out at dusk or dawn. Horses can also be sprayed with fly spray, and owners are encouraged to change their water on a regular basis to prevent mosquitoes from gathering near their water trough.