The major class of illness spread by mosquitoes in Florida are the viral encephalitis viruses.


The symptoms associated with these viruses are similar, and include fever, generalized headache and confusion. The headache is often very severe and not relieved by over-the-counter pain medications. Soon after the onset of headache, the infected individual may lose touch with reality. Many patients hallucinate and act strangely. Some develop coma and won’t respond to voice or touch. When coma develops death may follow. Another frightening manifestation of viral encephalitis may be seizures.


Although vaccines for viral encephalitis are available for horses, none are presently available for humans. Other than supportive care such as intravenous fluids and bedrest, at the present time there is no treatment for mosquito-born viral encephalitis


The leading viruses causing viral encephalitis in Florida are West Nile virusEastern equine encephalitisSt. Louis Encephalitis, and Venezuelan equine encephalitis. Florida’s many bodies of standing water and warm temperatures make our state an ideal breeding ground for mosquitoes. Our state also harbors the two main hosts that serve as reservoirs for these viruses: birds and or horses. Florida prides itself in being the bird capital of the United States making this an ideal state for the spread of viral encephalitis. In addition, horse breeding has become a major industry. These conditions increase the likelihood that mosquitoes will spread these viruses from birds to horses, from birds to humans and from horses to humans.


The best way to prevent contracting these deadly viruses is to avoid mosquito bites. Long sleeves shirts and pants decrease the surfaces available for mosquitoes to bite. Try not be outdoors at sunrise and sunset, the times when mosquitoes usually feed. Finally if you must be outdoors for prolonged periods, administer insect repellant. Products containing DEET (N,N-diethyl-m-toluamide), Picaridin (KBR 3023) or oil of lemon eucalyptus are most effective.

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Prepared by Frederick Southwick, M.D.
Professor of Medicine and Chief of Infectious Diseases
University of Florida College of Medicine

For more information see Infectious Diseases in 30 Days, McGraw-Hill, 2003, pg 197-200.