Eastern Equine Encephalitis (EEE)

Eastern Equine Encephalitis – History

Eastern Equine Encephalitis (EEE), also known as sleeping sickness, was first recognized in 1831 when 75 horses died in Massachusetts.  The EEE virus was first isolated from horse brain in 1933.  Human cases were recognized in 1938 when 30 children died in the Northeast US.

Geography

Most cases occur in the Eastern US or Gulf Coast states as well as the upper Midwest.  Many cases are associated with hardwood swamps.  The virus is maintained in a mosquito-bird-mosquito cycle.  In the summer and early fall it is transmitted to humans by mosquitoes .  These mosquitoes are referred to as ‘bridge vectors’, as they ‘bridge’ the virus from birds to humans.  The virus cannot be transmitted human to human.

Eastern Equine Encephalitis - Mosquito Fun Facts

Eastern Equine Encephalitis – Impact on Public Health

About 30% of those who get Eastern Equine Encephalitis die, and those who survive have significant neurological impairment.  Those over the age of 50 and under 15 are at increased risk of severe disease, and infection provides life-long immunity.  There is no vaccine for humans.

Clinical illness presents in two forms:

  • A systemic illness, with symptoms much like influenza, that lasts 1-2 weeks with complete recovery
  • An encephalitic (inflammation of the brain) illness with restlessness, anorexia, vomiting, diarrhea, convulsions and coma.

2019 Update

The average number of cases per year is about 7.  However, in 2019 there have already been at least 27 cases in 6 states with 11 deaths (as of October 3rd).  Cases so far by state with deaths in parentheses include Massachusetts – 11 (4), Michigan – 8 (3), Connecticut – 4 (3), Rhode Island – 1 (1), New Jersey – 1, North Carolina – 1.

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Additional Resources

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