An Overview of Eastern Equine Encephalitis (EEE).

The research article focuses on Eastern equine encephalitis (EEE), a mosquito-borne virus prevalent in eastern North America and the Caribbean. It provides an overview of the virus’s transmission, its diagnosis, and the currently available treatment options.

Background Information on EEE

• The Eastern equine encephalitis (EEE) virus is an alphavirus transmitted by mosquitoes, and was first isolated from horses in 1933.
• EEE is most commonly found in eastern parts of North America and in the Caribbean, and it’s closely related to other viruses like the western equine encephalitis virus, the Venezuelan equine encephalitis virus, and the Madariaga virus.
• The first-known human cases of EEE were reported in Massachusetts in 1938.

Transmission of the Virus

• Bird populations residing near freshwater hardwood swamps are the primary carriers of the virus, with Culiseta melanura mosquitoes acting as the main vectors.
• Other species of mosquitoes, such as Aedes, Coquillettidia, and Culex spp., can get infected when feeding on these infected birds and go on to infect humans and horses.
• Organ transplantation is now identified as another potential path for the virus to spread to humans.

Spread and Occurrence of the Virus

• Reported cases of EEE in humans and horses frequently occur in the East Coast, Great Lakes, and Gulf Coast states.
• Infections typically peak from July to September, which corresponds with the mosquitoes’ peak activity period.
• Data from the US Centers for Disease Control and Prevention (CDC) show that 121 human cases were reported between 2003 and 2016.
• Approximately 7 human cases are reported each year, but this can range from 3 to 21, as EEE’s spread tends to occur in cycles.
• In 2019, 38 cases were reported, mostly from Michigan and Massachusetts, but the exact reason for this spike is unknown.

Symptoms, Diagnosis, and Treatment

• EEE virus infections can be asymptomatic or symptomatic, with the latter sometimes leading to systemic conditions like fever, fatigue, and joint pain.
• Approximately 5% of EEE virus infections can evolve into neuroinvasive diseases, which come with a high mortality rate of around 33%, leading to conditions like meningoencephalitis.
• The diagnostic process typically involves positive serology such as immunoglobulin M tests.
• While effective antiviral treatments for neuroinvasive EEE virus infections are lacking, symptomatic treatment which often involves intensive care management is applied to manage seizures, coma, and cerebral edema.

Prevention

• Preventing EEE virus infection is possible by evading mosquito bites via methods such as wearing insect repellant, avoiding outdoor activities between dusk and dawn, and wearing protective clothing.
• Healthcare professionals are advised to reach out to local or state health departments for any enquiries about EEE or assistance with confirmatory testing requirements.