Eastern Equine Encephalitis Virus in the United States, 2003-2016

Area of Science:

• Arbovirology
• Epidemiology
• Public Health

Background:

• Eastern equine encephalitis virus (EEEV) is a mosquito-borne alphavirus endemic to the eastern United States.
• EEEV infection in humans is rare but associated with severe, often fatal, neuroinvasive disease.
• Surveillance is crucial for understanding EEEV's epidemiology and geographic distribution.

Purpose of the Study:

• To summarize national Eastern equine encephalitis virus surveillance data from 2003 to 2016.
• To analyze human disease cases and nonhuman infections to understand EEEV activity.
• To inform public health interventions and clinical awareness.

Main Methods:

• Analysis of national surveillance data for EEEV activity, including human cases and nonhuman infections, from 2003–2016.
• Calculation of incidence rates and identification of demographic and geographic risk factors for human EEEV neuroinvasive disease.
• Review of case fatality ratios and hospitalization rates.

Main Results:

• EEEV activity was reported in 633 counties across 33 states; 88% showed activity only in nonhuman species.
• A total of 121 human cases were reported, with a median of 8 cases annually and an average incidence of 0.03 per million.
• Neuroinvasive disease incidence was highest in males, persons <5 and >60 years, with a 41% fatality rate, highest in those ≥70 years.

Conclusions:

• Nonhuman surveillance reveals a broader EEEV geographic range than human cases indicate.
• Clinicians should consider EEEV in differential diagnoses for meningitis and encephalitis in endemic areas.
• Prevention relies on mosquito control and personal protective measures due to the lack of human vaccines.