IAMAT |International Association of Medical Assistance to Travellers| IAMAT |International Association of Medical Assistance to Travellers|

Viral Encephalitis

Photo By: Carol Scott

Viral Encephalitis is a symptom caused by arthropod-borne viruses also known as arboviruses. These viruses, belonging to the Togaviridae, Flaviviridae, and Bunyaviridae families, are zoonoses (animal infections that can spread to humans) that are transmitted by mosquitoes, ticks, moth flies, and sand flies who feed on mammals and birds. Humans become ill when they get bitten by infected insects since the viruses target the Central Nervous System. Arboviruses are not transmitted from person to person.

Venezuelan Equine Encephalitis (VEE), Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), and La Crosse Encephalitis (LAC) are illnesses caused by infected mosquitoes while Powassan Encephalitis (POW) is caused by ticks. There is no vaccine or preventive medication against these illnesses.

>> Travel health advice for other arboviral illnesses: Japanese Encephalitis, Tick-Borne Encephalitis, and West Nile Virus


Arboviruses are found worldwide and the transmission period is seasonal, typically from Spring to Fall. Travellers involved in outdoor activities such as hiking, camping, ecotourism, and agricultural work are at greater risk. Persons with a weak immune system, children, and the elderly are more susceptible to the infection.


Most infections are asymptomatic (persons do not exhibit symptoms). Those who do, typically present flu-like symptoms including fever, headache, muscle pain, chills, nausea, vomiting, and general weakness within days of being bitten by an infected insect. In some patients, neurological symptoms can develop including confusion, convulsions, drowsiness, and behavioural changes. The illnesses can progress to inflammation of the brain, respiratory system disorders, coma, and sometimes death. Treatment includes supportive care of symptoms.


Travellers should take measures to prevent insect bites including a DEET-containing repellent to exposed skin, applying permethrin spray (or solution) to clothing and gear, wearing long sleeves and pants. Get rid of water containers around dwellings and ensuring that door and window screens work properly to avoid mosquito bites.

To prevent tick bites, stay away from tall grasses and shrubs. Wear light coloured clothing, and long shirts and pants tucked into socks. Carefully examine your clothing, gear, and pets for ticks before entering a dwelling. Regularly check your body for ticks and promptly remove using tweezers by grasping the tick's head and mouth parts as much as possible and by pulling perpendicular from the skin. Thoroughly disinfect the bite site with soap and water or alcohol. If travelling in an endemic area, you may want to save the tick in a zip-lock bag or empty container to have it analyzed through your healthcare practitioner.

Health risk description last reviewed: November 5, 2014
Country information last updated: August 18, 2016


Viral Encephalitis has been reported in:

Travel Health Journal