Japanese encephalitis

• Japanese encephalitis (JE) is the most common vaccine-preventable cause of encephalitis in Asia with estimated 100 000 clinical cases each year.^(1,2)
• JE is endemic in 25 countries in Asia and the Western Pacific.⁽³⁾
• Japanese encephalitis virus (JEV) is transmitted to humans through bites from infected mosquitoes of the Culex species (mainly Culex tritaeniorhynchus).⁽¹⁾
• JEV-infection can result in febrile illness or neurologic disease, including meningitis or encephalitis.⁽⁴⁾
• The case-fatality rate can be as high as 30% among those with disease symptoms.^(1.2)
• Among survivors, 30%–50% have serious neurologic, cognitive, or psychiatric sequelae.^(1.2)
• There is currently no antiviral treatment for JE.^(1.2)
• Travelers should take further precautions to avoid mosquito bites. Personal preventive measures include the use of mosquito repellents and wearing long-sleeved clothing.^(1,2)
• The Austrian vaccination schedule recommends vaccination for travelers to endemic areas of Asia.⁽⁵⁾
• Before traveling, check possible preventive measures. The platform www.reisemedizincheck.at can help you find a travel medicine expert in your area.

Japanese encephalitis (JE) is a potentially serious disease, which is caused by the Japanese-Encephalitis-virus, a mosquito-borne Flavivirus, and is closely related to dengue, yellow fever and West Nile viruses.⁽¹⁾

JE is the main cause of viral encephalitis in Asia.⁽¹⁾

JEV is transmitted to humans through the bites from infected mosquitoes of the Culex species (mainly Culex tritaeniorhynchus).⁽¹⁾

The virus is maintained in an enzootic cycle between mosquitoes and amplifying vertebrate hosts, primarily pigs and wading birds.^(1,2)

JE is endemic in 25 countries across Asia and parts of the western Pacific.⁽³⁾

The area of transmission of JE virus has expanded in recent years, most notably in Australia, with widespread areas of transmission detected during 2021–2022.(2) The risk areas in Australia include the following regions: Outer Torres Strait Islands, Tiwi Islands, and some areas of the mainland (parts of New South Wales, Victoria, Queensland, South Australia, and the Northern Territory).⁽³⁾

Transmission of the virus through mosquitoes occurs in rural agricultural areas, often associated with rice cultivation and flood irrigation, but also in urban centers.⁽²⁾ In temperate areas of Asia, transmission is seasonal, and human disease usually peaks in summer and fall.⁽²⁾ In the subtropics and tropics, seasonal transmission varies with monsoon rains and irrigation practices and may be prolonged or even occur year-round.⁽²⁾