Eastern Equine Encephalitis Elijah Steres
Symptoms • Eastern Equine Encephalitis (EEE) is caused by infection with the Eastern Equine Encephalitis virus (EEEV). When infected, you could one of two types of diseases: systemic or encephalitic. • The systemic form has an abrupt onset. Symptoms may include chills, fever, malaise, arthralgia, and malaria. A systemic infection will usually last from 1 – 2 weeks, and you will have a complete recovery, as long as the central nervous system is not affected. • Symptoms of the encephalitic form vary according to age. Infants will have an abrupt onset, while older children and adults will only feel the symptoms after a few days of systemic illness. Symptoms may include fever, headache, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions and coma.
Causes • EEEV is maintained in a cycle between the Culisetamelanuramosquitoes and birds in freshwater hardwood swamps. The Cs. melanuramosquito feeds almost exclusively on birds, and is not a threat to humans. In order for humans to become infected, you must have a mosquito which feeds on both birds and people, acting as a bridge between the two species.
Transmission cycle of EEEV Diagram from the center for disease control and prevention
Fortunately, there is no chance of you becoming infected by being near someone who has EEEV. Mosquitoes are the only way of transmitting the disease. Humans are what is known as “dead end hosts”, meaning that the amount of virus in their blood is too little to infect mosquitoes. Horses, which often become infected, are also “dead end hosts” there is no risk of contracting EEEV by being near an infected horse.
Epidemiology • The first human epidemic of EEE was in 1938, in the southeastern region of Massachusetts. 35 people were infected, and 25 died. Cases of EEE occur relatively infrequently. The primary cycle, which I mentioned under causes, takes place in swampy areas where there are fewer humans. All residents of and visitors to areas with reported EEEV activity are at risk, especially if they spend more time outdoors. People over 50 and under 15 are at a greater risk of developing severe disease when infected with EEEV. Only about 4 - 5% of human EEEV infections lead to EEE. There is an average of 6 human cases annually, most of which are in Georgia, Massachusetts, and New Jersey. Reported EEEV cases are most common in and around freshwater hardwood swamps, in Atlantic and Gulf Coast States, and the Great Lakes Region, as shown below.
Cases reported by state, 1964-2009 Chart form the center for disease control and prevention
Average annual occurrence by county, 1996-2009 Chart from the center for disease control and prevention
EEE cases reported by year, 1964-2009 Chart from the center for disease control and prevention
Treatments • Due to the fact that there are so few human cases of EEE, doctors do not have enough information to make a vaccine (though there is one for horses). The only prevention method for humans is to avoid getting bitten by mosquitoes. If someone is believed to be infected they should see a doctor, be tested for EEE, and get treatment. Severe illness is usually treated by supportive therapy, which may include hospitalization, respiratory support, IV fluids, and prevention of other infections. Surviving EEEV is believed to grant lifelong immunity to further infection.