Updated

Four Florida residents have died from a mosquito-borne disease that normally afflicts horses, health officials reported on Tuesday as the swampy state enters peak season for mosquito-borne illnesses.

Health officials said last month that two Tampa-area residents had died from eastern equine encephalitis, a viral disease that inflames the brain.

Two additional deaths from the disease known as EEE have since been confirmed, one in the state capital of Tallahassee and one in the northwest Florida town of Sopchoppy.

The disease mostly affects unvaccinated horses but a handful of human deaths are recorded each year, according to the Centers for Disease Control and Prevention. There is no human vaccine for the disease, which kills a third of its human victims and often leaves survivors with significant brain damage.

The Florida Department of Health is also tracking two other less deadly mosquito-borne diseases, West Nile virus and dengue fever.

EEE and West Nile virus have been detected in 43 of Florida's 67 counties, while dengue cases have been confirmed in two south Florida counties, Monroe and Broward, according to the state Department of Health.

The dengue virus began showing up in Florida in 2009 after an absence since its last major outbreak in 1934. At least 28 confirmed cases of domestically transmitted dengue fever have been reported in Florida this year, along with 67 foreign-acquired cases. The disease is more prevalent in Central and South America.

Carina Blackmore, state public health veterinarian, said the number of mosquito bites to people, horses and livestock resulting in EEE or West Nile appears consistent with the last several years.

"The two things we try to relay are get rid of mosquitoes and avoid contact," said Blackmore, adding that August and September are peak seasons for most mosquito-borne illnesses.

State health officials are urging residents to avoid contact with mosquitoes by wearing protective clothing and using insect repellent, especially products that include DEET. Homeowners are also asked to remove standing water where mosquitoes breed.