|
|
Eastern
Equine Encephalitis Fact Sheet Updated!
Eastern Equine Encephalitis
(EEE) is a mosquito-borne viral disease. As the name suggests, EEE occurs
in the eastern half of the US. Because of the high case fatality rate,
it is regarded as one of the more serious mosquito-borne diseases in the
United States.
TRANSMISSION:
What is the EEE transmission cycle? How do people become infected with
EEE virus?
- EEE virus is transmitted
to humans through the bite of an infected mosquito.
- The main EEE transmission
cycle is between birds and mosquitoes.
- Several species
of mosquitoes can become infected with EEE virus. The most important
mosquito in maintaining the enzootic (animal-based, in this case bird-mosquito-bird)
transmission cycle is Culiseta melanura.
- Horses can become
infected with, and die from, EEE virus infection.
ETIOLOGIC AGENT:
What causes EEE?
- Eastern equine
encephalitis virus is a member of the family Togaviridae, genus
Alphavirus.
- Closely related
to Western and Venezuelan equine encephalitis viruses
HUMAN CLINICAL
FEATURES: What type of illness can occur?
- Symptoms range
from mild flu-like illness to encephalitis (inflammation of the brain),
coma and death
- The EEE case fatality
rate (the % of persons who develop the disease who will die) is 35%,
making it one of the most pathogenic mosquito-borne diseases in the
US
- It is estimated
that 35% of people who survive EEE will have mild to severe neurologic
deficits
INCIDENCE: How
many and where have human disease cases occurred?
- 200 confirmed
cases in the US 1964-present
- Average of 4 cases/year,
with a range from 0-14 cases
- States with largest
number of cases are Florida, Georgia, Massachusetts, and New Jersey.
- The enzootic (animal-based)
transmission cycle is most common to coastal areas and freshwater swamps.
- Human cases occur
relatively infrequently, largely because the primary transmission cycle
takes place in swamp areas where populations tend to be limited.
RISK GROUPS: Who
is at risk for developing EEE?
- Residents of and
visitors to endemic areas (areas with an established presence of the
virus)
- People who engage
in outdoor work and recreational activities
- Persons over age
50 and younger than age 15 seem to be at greatest risk for developing
severe disease
PREVENTION: How
can people avoid infection with EEE virus?
- A vaccine is available
to protect equines
- People should
avoid mosquito bites by employing personal and household protection
measures, such as using insect repellent containing DEET, wearing protective
clothing, taking precautions from dusk to dawn when mosquitoes are most
likely to bite, and controlling standing water that can provide mosquito
breeding sites. For more information about preventing mosquito-borne
disease see Preventing West
Nile Virus.
SURVEILLANCE:
How is EEE monitored?
- EEE is reportable
under the National Notifiable Diseases Surveillance System
- In 2003, EEE cases
are being reported to ArboNet for the first time. ArboNet is the national,
electronic surveillance system established by CDC to assist states in
tracking West Nile virus and other mosquito-borne viruses.
- Data for 1964-2000
is posted on this website, by state, as is a map
of cases from 1964-1997.
TRENDS
- Risk of exposure
to infected mosquitoes increases as population expands into areas with
an established presence of the virus
CHALLENGES
- There is no licensed
vaccine for human use
- There are no effective
therapeutic drugs
- Unknown overwintering
cycle
- Control measures
expensive
- Limited financial
support of surveillance and prevention
RESEARCH PRIORITIES
- Improve predictive
capabilities
- Develop and evaluate
vaccines
- Develop and evaluate
therapeutic drugs
- Improve diagnostic
and virus detection tests
Return to top of page
|