Japanese encephalitis (JE) virus, a flavivirus, is closely related to West Nile and St. Louis encephalitis viruses. JE virus is transmitted to humans through the bite of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus.
The virus is maintained in a cycle between mosquitoes and vertebrate hosts, primarily pigs and wading birds (also referred to as amplifying hosts or natural reservoirs). Humans are incidental or dead-end hosts because they usually do not develop high enough concentrations of the JE virus in their bloodstream to infect feeding mosquitoes.
JE virus transmission occurs primarily in rural agricultural areas, often associated with rice production and flooding irrigation. In some areas of Asia, these conditions can occur near urban centres.
In temperate areas of Asia, JE virus transmission is seasonal. The human disease usually peaks in the summer and fall. In the subtropics and tropics, transmission can occur year-round, often with a peak during the rainy season.
You cannot catch JE through contact with infected people or animals. You also cannot catch it by eating meat from an infected animal.
Less than 1% of people infected with the Japanese encephalitis (JE) virus develop a neurologic illness.
In persons who develop symptoms, the time from infection until illness onset (incubation period) is typically 5-15 days. Though most people who get JE do not have any symptoms, these can include:
People with a severe infection (1 in every 250 people) may get symptoms such as:
⚠️ Among those who get a serious illness, some may have lifelong neurological complications or even death.
Who is at Risk?
Those who are more likely to get the Japanese encephalitis (JE) virus are:
people who work or do outside activities (e.g. camping, fishing, hiking, gardening) in high-risk areas.
people working at and, or living close to piggeries (if infected by a mosquito, pigs can get high levels of the virus, and infect more mosquitoes if bitten)
The Centers for Disease Control and Prevention (CDC) website includes a map indicating areas of risk for the Japanese encephalitis (JE) virus - here.
Travellers can get the Japanese encephalitis (JE) virus vaccine and take steps to prevent mosquito bites.
⚕️ People planning to visit Japanese encephalitis (JE) virus-affected areas should seek advice from their doctor or a travel clinic at least 4-6 weeks before departing.
Protect yourself against mosquitoes and the risk of diseases they transmit:
Cover up while outside - wear loose, long-sleeved, light-coloured clothing, covered footwear, and socks. Mosquitoes can bite through tight clothing.
Treat clothing and gear with permethrin - Use 0.5% permethrin to treat clothing and gear (such as boots, pants, socks, and tents) or buy permethrin-treated clothing and gear. The Centers for Disease Control and Prevention (CDC) website includes details about how to use permethrin - here
Apply mosquito repellent evenly to all areas of exposed skin.
The most effective repellents contain picaridin, DEET or oil of lemon eucalyptus. Natural or homemade repellents provide limited protection. Read the instructions to find out how often you should reapply repellent. Always apply sunscreen first and then apply repellent. Take special care during peak mosquito-biting hours.
The mosquitoes that transmit diseases such as malaria can live indoors and bite during the day and night.
Stay and sleep in screened or air-conditioned rooms
Use a bed net if the area where you are sleeping is exposed to the outdoors.
Nets are most effective when they are treated with a pyrethroid insecticide, such as permethrin. Pre-treated bed nets can be purchased before travelling, or nets can be treated after purchase.
Avoid known areas of high mosquito-borne disease transmission or outbreaks.
Discover more about Japanese Encephalitis at the following sites:
General Travel Advice Disclaimer - here.