Venezuelan equine encephalitis virus infection

Venezuelan equine encephalitis virus infection is a mosquito-borne virus that usually causes mild and self-limiting disease in humans, characterised by symptoms that resemble influenza or dengue fever (e.g., fever, headache, malaise, nausea). Central nervous system infection can lead to long-term neurological sequelae and death, particularly in children.

Occurs mainly in Central and South America, but cases have been reported in North America.

Large human outbreaks have been linked to epizootic infection, in which equine species are a major amplifying host for the virus. Enzootic infection, which likely utilises rodents as amplifying hosts, may cause up to 10% of cases clinically misdiagnosed as dengue fever.

Diagnosis is based on clinical presentation and geographical clues. Confirmation of diagnosis is via reverse transcription-polymerase chain reaction, viral isolation, or serology. Differentiation from malaria and dengue fever is essential.

There is no specific treatment; supportive care is advocated.

Avoidance of mosquito bites is the best method of prevention. There is no licensed vaccine for use in humans, although a live-attenuated vaccine is available for laboratory personnel at risk of occupational exposure.

Infection caused by Venezuelan equine encephalitis virus (VEEV), a positive-sense single-stranded RNA virus (family: Togaviridae; genus: Alphavirus) transmitted by mosquitoes. Mosquitoes transmit the virus by feeding on the blood of animals infected with VEEV (horse or rodent) and passing it on to non-infected humans or animals when it feeds again. 

In humans infected with VEEV, the incubation period ranges from 1 to 10 days, and the duration of acute illness is typically days to weeks, depending on severity.[1]Centers for Disease Control and Prevention. Biosafety in microbiological and biomedical laboratories (BMBL) 6th edition. May 2024 [internet publication]. https://www.cdc.gov/labs/bmbl VEEV infection may be asymptomatic or result in mild self-limiting symptoms that resemble influenza or dengue fever (e.g., fever, malaise, headache, nausea); however, some infections may result in more serious neurological complications (e.g., seizures and coma), haemorrhage, or death. Overall mortality during outbreaks of VEEV has rarely exceeded 1%.[1]Centers for Disease Control and Prevention. Biosafety in microbiological and biomedical laboratories (BMBL) 6th edition. May 2024 [internet publication]. https://www.cdc.gov/labs/bmbl ​ Mortality occurs mainly in children and is generally attributable to consequences of neurological involvement.[2]Quiroz E, Aguilar PV, Cisneros J, et al. Venezuelan equine encephalitis in Panama: fatal endemic disease and genetic diversity of etiologic viral strains. PLoS Negl Trop Dis. 2009 Jun 30;3(6):e472. https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0000472 http://www.ncbi.nlm.nih.gov/pubmed/19564908?tool=bestpractice.com

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