Japanese encephalitis (JE) is a viral disease spread by mosquitoes (Culex) and found primarily in rural areas of Southeast Asia, although reports have been scattered all over Asia. This infection has an affinity for the brain and spinal cord tissues as is know to causes meningitis like symptoms including headache, neck stiffness, fever and malaise. A majority of these infections are asymptomatic although JE carries a 0.3-60% case fatality rate. Infants are a particularly vulnerable population and often hardest hit. Pigs and birds are a key reservoir of the illness, making visitors to rural farming areas at particular risk. 30,000 to 50,000 people are affected each year with 10,000 too 15,000 deaths.
Japanese encephalitis is a vaccine preventable disease. A vaccine is licensed in the USA, under the name JE-VAX but has been difficult to obtain due to shortages and decreased production. However, a new vaccine against Japanese encephalitis was approved by the FDA March 31, 2009, called IXIARO and manufactured in the UK. This will be the only vaccine against Japanese Encephalitis in the USA. Research showed that only two doses of the newer generation vaccine were needed to provide adequate protection versus three does with JE-VAX. A copy of the InterCell (manufacturer) press release can be read here.
Who Needs It?
Most travelers to Asia do not require the JE vaccine. This illness is not considered a risk for short-term travelers to urban areas and developed resort areas. Those traveling to remote/rural areas (especially farming communities) during the rain season are the adventurers who should receive this vaccine. Also, travel to an area with a previous outbreak of JE should prompt discussion about being vaccinated with your expedition/travel doctor. Estimated risk of travelers to rural areas during transmission season is about 1 in 5,000 per day.
As with any mosquito-borne illness, preventing mosquito bites is a key step and should be done by all, regardless of being vaccinated. Long sleeves and pants, avoiding peak biting times (dawn/dusk) and use of insect repellents are critical. Bed nets are also another key ingredient for travelers sleeping in open areas.