Florida has been hit hardest, with a total of 174 equine cases reported from 47 counties as of July 25. The outcome of 163 of those cases is known: About 66% of those cases died or were euthanized. The EEE mortality rate is up to 90% in some areas and veterinarians continue to advise horse owners to vaccinate their animals against the disease.

EEE, which is spread by the bites of infected mosquitoes, began hitting the news this year in early April, when the first equine cases were reported in Florida. Bumper mosquito crops, warmer temperatures, and rains producing mosquito-breeding havens have been implicated in the unusual spread of the illness this year. However, veterinarians in the Southeast have said that the disease is cyclic and that they were due a difficult EEE year.
Other states experiencing their share of EEE include Alabama, Georgia, North Carolina, South Carolina, and Mississippi. Tennessee and Virginia have recently reported their first equine cases of EEE for 2003. On July 22, Indiana detected EEE in a robin.

North Carolina's state health director, Leah Devlin, MPH, DDS, said on July 22, "Eastern equine encephalitis has showed up earlier this year and in far greater numbers than in the past. We have seen it in horses, chickens, or mosquito pools from 20 North Carolina counties."

Venaye P. Reece, DVM, equine programs coordinator and state animal emergency response coordinator with South Carolina's state veterinarian's office, said her state "has nearly 70 lab-confirmed EEE cases in horses, and numbers are increasing almost daily. The majority of the cases are still in the lower half of the state, but are widespread," said Reece. She added that most of the cases are in non-vaccinated or not recently vaccinated horses.

"We encourage immediate vaccination of horses not current on EEE and West Nile virus (WNV) vaccination, and also mosquito protection and control measures that best fit the situation, for protection of both horses and humans," she said. South Carolina officials are concerned that this outbreak could extend into early fall, since the EEE cases began trickling in so early in the mosquito season.