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SECTION I - INFECTIOUS AGENT
NAME: Eastern equine encephalitis virus, Western equine encephalitis virus
SYNONYM OR CROSS REFERENCE: Eastern equine encephalomyelitis, Western equine encephalomyelitis, EEE, WEE,
arbovirus.
CHARACTERISTICS: 70 nm diameter, ssRNA, enveloped; Togaviridae, Genus Alphavirus.
SECTION II - HEALTH HAZARD
PATHOGENICITY: Acute inflammatory disease of short duration involving brain, spinal cord, and meninges;
most infections are asymptomatic; severe infections marked by acute onset headache, high fever, meningeal signs,
stupor, disorientation, coma, spasticity, tremors, convulsions and paralysis; up to 60% case fatality rate (lower
fatality rate for WEE).
EPIDEMIOLOGY: EEE in eastern and north central North America, scattered areas of Central and South America
and in Caribbean; WEE in western and central North America and Argentina; cases occur in temperate latitudes in
summer and early fall, and are limited to areas and years of high temperature and many mosquitoes.
HOST RANGE: Humans, horses, other animals, birds.
INFECTIOUS DOSE: Unknown
MODE OF TRANSMISSION: By the bite of infective mosquitoes.
INCUBATION PERIOD: Usually 5-15 days.
COMMUNICABILITY: Not directly transmitted from person to person; virus is not demonstrated in blood of humans
after onset of disease; viremia in birds 2-5 days- mosquitoes are infective for life; vire@a in horses rarely present
in high titers for long periods.
SECTION III - DISSEMINATION
RESERVOIR: Humans and horses are uncommon sources of mosquito infection; virus overwinters possibly in
birds, other animals; or survives in mosquito eggs (true reservoir unknown).
ZOONOSIS: Yes, from infected animals via mosquitoes.
VECTORS: EEE - Culiseta melanura (bird to bird).
Aedes spp., Coquillettidia spp. (bird or animal to man).
VECTORS: WEE - Culex tarsalis (major epidemic vector).
found in at least 5 genera of mosquitoes
SECTION IV - VIABILITY
DRUG SUSCEPTIBILITY: N/A
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to disinfectants - 1% sodium hypochlorite (20% commercial bleach),
2% glutaraldehyde, formaldehyde, 70% ethanol.
PHYSICAL INACTIVATION: Sensitive to moist and dry heat, desiccation.
SURVIVAL OUTSIDE HOST: Does not survive outside of fiost.
SECTION V - MEDICAL
SURVEILLANCE: Monitor for symptoms of arthropod-borne viral fever; serological identification and antibody
titer.
FIRST AID/TREATMENT: No specific treatment, supportive measures.
IMMUNIZATION: Investigational vaccines available and recommended for personnel who work directly and regularly
with EEE and WEE in laboratory.
PROPHYLAXIS: WEE immunoglobulin (human) available but efficacy of product has not been established.
SECTION VI - LABORATORY HAZARDS
LABORATORY-ACQUIRED INFECTIONS: EEE - 4 reported cases; WEE - 7 reported cases with 2 deaths (associated
with egg cultures, suckling mice and aerosols - broken lyophilized material).
SOURCES/SPECIMENS: Blood, CSF, central nervous system and other tissues, infected arthropods.
PRIMARY HAZARDS: Accidental parenteral inoculation, contact with broken skin or mucous membranes, bites
of infected laboratory arthropods, infectious aerosols.
SPECIAL HAZARDS: Infection of newly hatched chickens is especially hazardous.
SECTION VIII - RECOMMENDED PRECAUTIONS
CONTAINMENT REQUIREMENTS: Biosafety level 3 practices, safety equipment, and facilities for activities
with potentially infectious clinical materials and arthropods, for manipulations of infected tissue cultures, embryonated
eggs and rodents, and for infection of newly hatched chickens.
PROTECTIVE CLOTHING: Laboratory coat; gloves and gown with tight wrists and tie in back should be worn while
working with infectious materials.
OTHER PRECAUTIONS: Vaccination of personnel working directly and regularly with EEE and WEE.
SECTION VIII - HANDLING INFORMATION
SPILLS: Allow aerosols to settle; wearing protective clothing, gently cover spill with paper towel and
apply 1% sodium hypochlorite (20% commercial bleach), starting at perimeter and working towards the center- allow
sufficient contact time before clean up (30 min.).
DISPOSAL: Decontaminate before disposal- steam sterilization, incineration.
STORAGE: In sealed containers that are appropriately labeled (in locked level 3 facility).
Date prepared: October 11, 1997 Prepared by.- Canadian Office of Biosafety Information edited by the Colorado State
University Office of Biosafety; June 16, 1998.
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