Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide


eastern equine encephalitis virus



eastern equine encephalitis virus


  • Last modified
  • 19 November 2019
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • eastern equine encephalitis virus
  • Taxonomic Tree
  • Domain: Virus
  •   Group: "Positive sense ssRNA viruses"
  •     Group: "RNA viruses"
  •       Family: Togaviridae
  •         Genus: Alphavirus
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Preferred Scientific Name

  • eastern equine encephalitis virus

English acronym

  • EEEV
  • EEV

Taxonomic Tree

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  • Domain: Virus
  •     Group: "Positive sense ssRNA viruses"
  •         Group: "RNA viruses"
  •             Family: Togaviridae
  •                 Genus: Alphavirus
  •                     Species: eastern equine encephalitis virus

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Last updated: 07 Jan 2022
Continent/Country/Region Distribution Last Reported Origin First Reported Invasive Reference Notes


AlgeriaAbsent, No presence record(s)Jul-Dec-2019
AngolaAbsent, No presence record(s)Jul-Dec-2018
BeninAbsent, No presence record(s)Jan-Jun-2019
BotswanaAbsent, No presence record(s)Jul-Dec-2018
Burkina FasoAbsent, No presence record(s)Jul-Dec-2019
BurundiAbsent, No presence record(s)Jul-Dec-2018
Cabo VerdeAbsent, No presence record(s)Jul-Dec-2019
Central African RepublicAbsent, No presence record(s)Jul-Dec-2019
ChadAbsent, No presence record(s)Jul-Dec-2019
ComorosAbsent, No presence record(s)Jan-Jun-2018
Congo, Republic of theAbsent, No presence record(s)Jan-Jun-2019
Côte d'IvoireAbsent, No presence record(s)Jul-Dec-2019
DjiboutiAbsent, No presence record(s)Jul-Dec-2019
EgyptAbsent, No presence record(s)Jul-Dec-2019
EritreaAbsent, No presence record(s)Jul-Dec-2019
EswatiniAbsent, No presence record(s)Jul-Dec-2019
EthiopiaAbsent, No presence record(s)Jul-Dec-2018
GhanaAbsent, No presence record(s)Jan-Jun-2019
GuineaAbsent, No presence record(s)Jan-Jun-2019
Guinea-BissauAbsent, No presence record(s)Jul-Dec-2019
KenyaAbsent, No presence record(s)Jul-Dec-2019
LesothoAbsent, No presence record(s)Jan-Jun-2020
LibyaAbsent, No presence record(s)Jul-Dec-2019
MadagascarAbsent, No presence record(s)Jan-Jun-2019
MaliAbsent, No presence record(s)Jul-Dec-2019
MauritaniaAbsent, No presence record(s)Jul-Dec-2018
MauritiusAbsent, No presence record(s)Jul-Dec-2019
MayotteAbsent, No presence record(s)Jul-Dec-2019
MoroccoAbsent, No presence record(s)Jul-Dec-2019
MozambiqueAbsent, No presence record(s)Jul-Dec-2019
NamibiaAbsent, No presence record(s)Jul-Dec-2019
NigerAbsent, No presence record(s)Jul-Dec-2019
NigeriaAbsent, No presence record(s)Jul-Dec-2019
RéunionAbsent, No presence record(s)Jul-Dec-2019
RwandaAbsent, No presence record(s)Jul-Dec-2018
Saint HelenaAbsent, No presence record(s)Jan-Jun-2019
São Tomé and PríncipeAbsent, No presence record(s)Jul-Dec-2019
SenegalAbsent, No presence record(s)Jul-Dec-2019
SeychellesAbsent, No presence record(s)Jul-Dec-2018
Sierra LeoneAbsent, No presence record(s)Jan-Jun-2018
SomaliaAbsent, No presence record(s)Jul-Dec-2020
South AfricaAbsent, No presence record(s)Jul-Dec-2019
South SudanAbsent, No presence record(s)Jan-Jun-2018
SudanAbsent, No presence record(s)Jul-Dec-2019
TanzaniaAbsent, No presence record(s)Jul-Dec-2019
TogoAbsent, No presence record(s)Jul-Dec-2019
TunisiaAbsent, No presence record(s)Jul-Dec-2019
UgandaAbsent, No presence record(s)Jul-Dec-2019
ZambiaAbsent, No presence record(s)Jul-Dec-2018
ZimbabweAbsent, No presence record(s)Jul-Dec-2019


AfghanistanAbsent, No presence record(s)Jul-Dec-2019
ArmeniaAbsent, No presence record(s)Jul-Dec-2019
AzerbaijanAbsent, No presence record(s)Jul-Dec-2019
BahrainAbsent, No presence record(s)Jul-Dec-2020
BangladeshAbsent, No presence record(s)Jan-Jun-2020
BhutanAbsent, No presence record(s)Jan-Jun-2020
BruneiAbsent, No presence record(s)Jul-Dec-2019
CambodiaAbsent, No presence record(s)Jul-Dec-2019
ChinaAbsent, No presence record(s)Jul-Dec-2018
Hong KongAbsentJul-Dec-2019
IndonesiaAbsent, No presence record(s)Jul-Dec-2019
IranAbsent, No presence record(s)Jan-Jun-2019
IraqAbsent, No presence record(s)Jul-Dec-2019
IsraelAbsent, No presence record(s)Jul-Dec-2020
JapanAbsent, No presence record(s)Jan-Jun-2020
JordanAbsent, No presence record(s)Jul-Dec-2018
KazakhstanAbsent, No presence record(s)Jul-Dec-2019
KuwaitAbsent, No presence record(s)Jan-Jun-2019
LaosAbsent, No presence record(s)Jan-Jun-2019
LebanonAbsent, No presence record(s)Jul-Dec-2019
MalaysiaAbsent, No presence record(s)Jan-Jun-2019
MaldivesAbsent, No presence record(s)Jan-Jun-2019
MongoliaAbsent, No presence record(s)Jan-Jun-2019
MyanmarAbsent, No presence record(s)Jul-Dec-2019
NepalAbsent, No presence record(s)Jul-Dec-2019
PakistanAbsent, No presence record(s)Jan-Jun-2020
PalestineAbsent, No presence record(s)Jul-Dec-2019
QatarAbsent, No presence record(s)Jul-Dec-2019
Saudi ArabiaAbsent, No presence record(s)Jan-Jun-2020
SingaporeAbsent, No presence record(s)Jul-Dec-2019
South KoreaAbsent, No presence record(s)Jul-Dec-2019
Sri LankaAbsentJul-Dec-2018
SyriaAbsent, No presence record(s)Jul-Dec-2019
TaiwanAbsent, No presence record(s)Jul-Dec-2019
TurkeyAbsent, No presence record(s)Jul-Dec-2019
United Arab EmiratesAbsent, No presence record(s)Jul-Dec-2020
UzbekistanAbsent, No presence record(s)Jul-Dec-2019
VietnamAbsent, No presence record(s)Jul-Dec-2019


AlbaniaAbsent, No presence record(s)Jul-Dec-2019
AndorraAbsent, No presence record(s)Jul-Dec-2019
AustriaAbsent, No presence record(s)Jul-Dec-2019
BelgiumAbsent, No presence record(s)Jul-Dec-2019
Bosnia and HerzegovinaAbsent, No presence record(s)Jul-Dec-2019
BulgariaAbsent, No presence record(s)Jan-Jun-2019
CroatiaAbsent, No presence record(s)Jul-Dec-2019
CyprusAbsent, No presence record(s)Jul-Dec-2019
CzechiaAbsent, No presence record(s)Jul-Dec-2019
DenmarkAbsent, No presence record(s)Jan-Jun-2019
EstoniaAbsent, No presence record(s)Jul-Dec-2019
Faroe IslandsAbsent, No presence record(s)Jul-Dec-2018
FinlandAbsent, No presence record(s)Jul-Dec-2019
FranceAbsent, No presence record(s)Jul-Dec-2019
GermanyAbsent, No presence record(s)Jul-Dec-2019
GreeceAbsent, No presence record(s)Jan-Jun-2018
HungaryAbsent, No presence record(s)Jul-Dec-2019
IcelandAbsent, No presence record(s)Jul-Dec-2019
IrelandAbsent, No presence record(s)Jul-Dec-2019
ItalyAbsent, No presence record(s)Jul-Dec-2020
LatviaAbsent, No presence record(s)Jul-Dec-2020
LiechtensteinAbsent, No presence record(s)Jul-Dec-2019
LithuaniaAbsent, No presence record(s)Jul-Dec-2019
MaltaAbsent, No presence record(s)Jan-Jun-2019
MoldovaAbsent, No presence record(s)Jan-Jun-2020
MontenegroAbsent, No presence record(s)Jul-Dec-2019
NetherlandsAbsent, No presence record(s)Jul-Dec-2019
North MacedoniaAbsent, No presence record(s)Jul-Dec-2019
NorwayAbsent, No presence record(s)Jul-Dec-2019
PolandAbsent, No presence record(s)Jan-Jun-2019
PortugalAbsent, No presence record(s)Jul-Dec-2019
RomaniaAbsent, No presence record(s)Jul-Dec-2018
RussiaAbsent, No presence record(s)Jan-Jun-2020
San MarinoAbsent, No presence record(s)Jan-Jun-2019
SerbiaAbsent, No presence record(s)Jul-Dec-2019
SlovakiaAbsent, No presence record(s)Jul-Dec-2020
SloveniaAbsent, No presence record(s)Jul-Dec-2018
SpainAbsent, No presence record(s)Jul-Dec-2020
SwedenAbsent, No presence record(s)Jul-Dec-2020
SwitzerlandAbsent, No presence record(s)Jul-Dec-2020
UkraineAbsent, No presence record(s)Jul-Dec-2020
United KingdomAbsent, No presence record(s)Jul-Dec-2019

North America

BahamasAbsent, No presence record(s)Jul-Dec-2018
BarbadosAbsent, No presence record(s)Jul-Dec-2020
CanadaPresent, LocalizedJul-Dec-2019
Cayman IslandsAbsentJan-Jun-2019
Costa RicaAbsentJul-Dec-2019
CuraçaoAbsent, No presence record(s)Jan-Jun-2019
Dominican RepublicAbsentJan-Jun-2019
El SalvadorAbsentJul-Dec-2019
GreenlandAbsent, No presence record(s)Jul-Dec-2018
HaitiAbsent, No presence record(s)Jul-Dec-2019
MartiniqueAbsent, No presence record(s)Jul-Dec-2019
NicaraguaAbsent, No presence record(s)Jul-Dec-2019
Saint LuciaAbsent, No presence record(s)Jul-Dec-2018
Saint Vincent and the GrenadinesAbsent, No presence record(s)Jan-Jun-2019
Trinidad and TobagoAbsent, No presence record(s)Jan-Jun-2018
United StatesPresent, LocalizedJul-Dec-2019


AustraliaAbsent, No presence record(s)Jul-Dec-2019
Cook IslandsAbsent, No presence record(s)Jan-Jun-2019
Federated States of MicronesiaAbsent, No presence record(s)Jan-Jun-2019
French PolynesiaAbsent, No presence record(s)Jan-Jun-2019
KiribatiAbsent, No presence record(s)Jan-Jun-2018
Marshall IslandsAbsent, No presence record(s)Jan-Jun-2019
New CaledoniaAbsent, No presence record(s)Jul-Dec-2019
New ZealandAbsent, No presence record(s)Jul-Dec-2019
PalauAbsent, No presence record(s)Jul-Dec-2020
SamoaAbsent, No presence record(s)Jan-Jun-2019
Timor-LesteAbsent, No presence record(s)Jul-Dec-2018
VanuatuAbsent, No presence record(s)Jan-Jun-2019

South America

ArgentinaAbsent, No presence record(s)Jul-Dec-2019
BrazilPresent, LocalizedJul-Dec-2019
ChileAbsent, No presence record(s)Jan-Jun-2019
Falkland IslandsAbsent, No presence record(s)Jul-Dec-2019
ParaguayAbsent, No presence record(s)Jul-Dec-2019
PeruAbsent, No presence record(s)Jan-Jun-2019

Pathogen Characteristics

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The virus of eastern equine encephalitis belongs to the genus Alphavirus, formerly group A arboviruses, in the family Togaviridae. There are 26 confirmed members of the genus Alphavirus, including western equine encephalitis virus and Venezuelan equine encephalitis virus. Serological and phylogenetic analyses of representatives of North and South American eastern equine encephalitis virus varieties, spanning the entire temporal and geographic range available were carried out (Brault et al., 1999). Nucleotide sequencing and phylogenetic analyses revealed additional genetic diversity within the South American variety; 3 major South/Central American lineages were identified including one represented by a single isolate from eastern Brazil, and 2 lineages with more widespread distributions in Central and South America. All North American isolates comprised a single, highly conserved lineage with strains grouped by the time of isolation and partly by location. An eastern equine encephalitis strain isolated during a 1996 equine outbreak in Tamaulipas State, Mexico, was closely related to recent Texas isolates, suggesting southward EEV transportation beyond the presumed enzootic range. Plaque reduction neutralization tests with representatives from the 4 major lineages indicated that each represented a distinct antigenic subtype. As a results, a taxonomic revision of the eastern equine encephalitis complex was proposed. The new nucleotide sequences were deposited in the EMBL/GenBank/DDBJ database under accession numbers AF159550, AF159553-AF159559, AF159561 and AF160169-AF160180.

The viral particles (60-64 nm in diameter) consist of a single-stranded positive-sense RNA genome enclosed within an icosahedral nucleocapsid (30-35 nm in diameter) that is in turn enclosed within a host cell-derived plasma membrane envelope (Biberstein and Zee, 1990). The virion core is composed of a single core protein; the envelope shows peplomers consisting of two glycoproteins (E1 and E2). Glycoprotein E2 appears to carry the major neutralization and haemagglutination epitopes. E1 also has some (probably minor) neutralizing and haemagglutinating epitopes. E1 may also be responsible for generating strain diversity. Razumov et al. (1994), studied the haemagglutination domains of eastern equine encephalitis with 17 HI monoclonal antibodies (MAbs). A highly conserved domain (C domain) forming alphavirus-group-reactive MAbs was identified in the E2 protein of the eastern equine encephalitis virus. Amino acid residues 59 and 232 were shown to be involved in the formation of the C region.

The virus can be propagated in a variety of cell cultures including chick and duck fibroblasts, VERO, BHK, L cells and mosquito cells: cytopathology is often absent in the latter. A variety of lab animals can be experimentally infected, suckling mice being the most common. Embryonated chicken eggs and young chicks may also be susceptible to infection (Biberstein and Zee, 1990).

Pereboev et al. (1993) prepared 33 MAbs interacting with the structural proteins of the virus of eastern equine encephalitis. The mutual arrangement of antigenic sites on E1 and E2 glycoproteins was studied by competitive radioimmunoassay. At least 4 non-overlapping sites were found on E1. The E2 glycoprotein had at least 7 partially overlapping antigenic sites. MAbs to sites E2-2 and E2-3 neutralized viral infectivity and blocked haemagglutination. MAbs to the sites E2-1 blocked haemagglutination. MAbs to the sites E2-2, E2-3 and E2-7 protected mice against lethal infection although the protective sites to E2-2b and E2-7 did not neutralize the virus. Antibodies to the other 3 sites of E2 and to all sites of E1 showed no biological activity. The results demonstrated the dominant role of E2 in antiviral immunity; over 98% of the protective effect was associated with the E2-2 site.

Virus neutralization and haemagglutination inhibition have shown two antigenic variants of eastern equine encephalitis. The alphaviruses are sensitive to lipid solvents, chlorine, phenol and heating to 60ºC for 30 minutes. They are relatively insensitive to trypsin and are stabilized in buffer (pH7.6) in 50% glycerine. Virus can be held indefinitely at 4ºC in the lyophilized state (Biberstein and Zee, 1990).

The arbovirus cycles between vertebrate amplifying hosts and invertebrate vectors. Cooper and Scott (2001) examined the selective pressure associated with virus replication in either host and found that the virus is capable of host specific evolution when assayed in either mosquito or avian cells. Virus lineages grown in alternation between the 2 cell types expressed intermediate phenotypes consistent with dual adaptation to both cellular environments. Alternation of hosts selects for virus populations well adapted for replication in both host systems. Weaver et al. (1999) also examined host evolution and found that alternating host transmission cycles constrain the evolutionary rates of arboviruses but not their fitness for either host alone.

Monoclonal antibodies against western equine encephalitis have been shown to cross react with eastern equine encephalitis (Long et al., 2000). Western equine encephalitis has previously been shown to have arisen by recombination between eastern equine encephalitis and Sindbis-like viruses (Weaver et al., 1997). Nigerian equine encephalitis virus and some alphaviruses, such as western equine encephalitis, eastern equine encephalitis, Semliki Forest virus and Igbo-Ora virus are antigenically similar and related, implying NEEV is also an alphavirus (Adeyefa and Tomori, 1997.)

Host Animals

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Animal nameContextLife stageSystem
Agelaius phoeniceus (red-winged blackbird)Wild host
Alectoris chukarWild host
AmphibiaWild host
Anas (ducks)Wild host
Bos indicus (zebu)Domesticated host
Bos taurus (cattle)Domesticated host
Canis familiaris (dogs)Domesticated host
Capra hircus (goats)Domesticated host
Cardinalis cardinalisWild host
CebidaeWild host
Columba livia (pigeons)Wild host
Coturnix coturnixExperimental settings
Coturnix japonica (Japanese quail)Domesticated host
Cyanocitta cristataWild host
Dromaius novaehollandiaeDomesticated host; Wild host
Egretta thulaWild host
EquusDomesticated host; Wild host
Equus caballus (horses)Domesticated host
Erithacus rubeculaWild host
Felis catus (cat)Domesticated host
Gallus gallus domesticus (chickens)Experimental settings
Grus americanaWild host
Homo sapiensWild host
Hylocichla mustelinaWild host
Meleagris gallopavo (turkey)Experimental settings
Melospiza georgianaWild host
Melospiza melodiaWild host
Mephitis mephitis (striped skunk)Wild host
MicrochiropteraWild host
Molothrus ater (brown-headed cowbird)Wild host
Mus musculus (house mouse)Wild host
Parus bicolorWild host
Parus carolinensisWild host
Passer domesticus (house sparrow)Wild host
PerdixWild host
Phasianus (pheasants)Domesticated host; Wild host
Phasianus colchicus (common pheasant)Domesticated host; Wild host
Picoides villosus (hairy woodpecker)Wild host
Plegadis falcinellusWild host
Quiscalus quisculaWild host
Reptilia (reptiles)Wild host
Struthio camelus (ostrich)Domesticated host; Wild host
Sturnus vulgaris (common starling)Wild host
Sus scrofa (pigs)Domesticated host
Turdus migratoriusWild host
Ursus americanusWild host
Vulpes vulpes (red fox)Wild host
Zenaida macrouraWild host

Vectors and Intermediate Hosts

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Adeyefa CAO; Tomori O, 1997. Serological analysis of Nigerian equine encephalitis virus. Veterinarski Arhiv, 67(2):77-85.

Biberstein EL; Zee YC, 1990. Review of Veterinary Microbiology. Boston, USA: Blackwell Scientific Publications.

Brault AC; Powers AM; Villarreal Chavez CL; Navarro Lopez R; Fraire Cachón M, 1999. Genetic and antigenic diversity among eastern equine encephalitis viruses from North, Central, and South America. American Journal of Tropical Medicine and Hygiene, 61(4):579-586.

Cooper LA; Scott TW, 2001. Differential evolution of eastern equine encephalitis virus populations in response to host cell type. Genetics, 157(4):1403-1412.

Long MC; Nagata LP; Ludwig GV; Alvi AZ; Conley JD; Bhatti AR; Suresh M, 2000. Construction and characterization of monoclonal antibodies against western equine encephalitis virus. Hybridoma, 19(2):121-127.

Pereboev AV; Agapov EV; Svyatchenko VA; Razumov IA; Protopopova EV; Loktev VB, 1993. Study of the antigenic structure of the virus of eastern equine encephalomyelitis using monoclonal antibodies. Voprosy Virusologii, 38(3):117-122.

Razumov IA; Khusainova AD; Agapov EV; Gaidamovich SY; Pereboev AV; Kolykhalov AA; Netesov SV; Loktev VB, 1994. Intervirology, 37(6):356-360.

Weaver SC; Brault AC; Kang WenLi; Holland JJ, 1999. Genetic and fitness changes accompanying adaptation of an arbovirus to vertebrate and invertebrate cells. Journal of Virology, 73(5):4316-4326.

Weaver SC; Kang WenLi; Shirako Y; Rümenapf T; Strauss EG; Strauss JH, 1997. Recombinational history and molecular evolution of western equine encephalomyelitis complex alphaviruses. Journal of Virology, 71(1):613-623.

Distribution References

OIE, 2018. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2018a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2019. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2019a. World Animal Health Information System (WAHIS): Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2020. World Animal Health Information System (WAHIS): Jul-Dec. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

OIE, 2020a. World Animal Health Information System (WAHIS). Jan-Jun. In: OIE-WAHIS Platform, Paris, France: OIE (World Organisation for Animal Health). unpaginated.

Distribution Maps

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