Venezuelan equine encephalitis virus infection

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 be the cause of up to 10% of cases that are 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 important.

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]Public Health Service; Centers for Disease Control and Prevention; National Institutes of Health. Biosafety in microbiological and biomedical laboratories 5th edition. December 2009 [internet publication]. https://www.cdc.gov/biosafety/publications/bmbl5/bmbl.pdf 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 have rarely exceeded 1%.[2]Weaver SC, Paessler S. Alphaviral encephalitides. In: Barrett ADT, Stanberry LR, eds. Vaccines for biodefense and emerging and neglected diseases. San Diego, CA: Elsevier; 2009:340-54. Mortality occurs mainly in children, and is generally attributable to consequences of neurological involvement.[3]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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