Japanese Encephalitis
What is it and how it is spread?
Japanese encephalitis is a viral infection of the brain, which is spread from animals and birds to humans by the bite of an infected mosquito. It is found in parts of Asia, the Indian subcontinent and the Pacific rim, especially in rural areas where rice paddies and pig farming are common. In affected countries, around 68,000 cases are thought to occur every year.1,2
Who is at risk?
The risk of getting Japanese encephalitis is very low for most travellers to Asia (less than one case per million), especially for short-term travellers visiting urban areas.2 Your risk of infection is higher if you plan to stay in an affected area for a long time, are visiting rural areas during the mosquito breeding season (usually the rainy season), are staying near rice paddies or pig farms, or are planning a lot of outdoor or night-time activities such as camping.1,2
What are the symptoms?
Most people who get Japanese encephalitis will not have any symptoms. When symptoms do occur, they generally come 5–15 days after the mosquito bite and include fever, headache, confusion and in severe cases, seizures. Although very rare, severe cases can be fatal, and up to half of survivors have neurological problems after recovery.1,2
How can it be prevented?
You can reduce the risk of getting Japanese encephalitis by using insect repellent, wearing clothes that cover your skin, and using mosquito nets during the night. You should take special care during the hours between dusk and dawn.1,2
A vaccine for Japanese encephalitis is available, and you should talk to your travel healthcare professional to discuss whether you should consider vaccination.1,2
As a precautionary measure, vaccination against Japanese encephalitis in pregnant and breastfeeding women should be avoided.2 However, travellers and their healthcare professional must make a risk assessment on the theoretical risks of vaccine in pregnancy against the potential risk of acquiring Japanese encephalitis.2
How can it be treated?
There is no specific antiviral treatment for Japanese encephalitis. Other treatments are aimed at improving comfort and reducing symptoms, while people occasionally need to be treated in an intensive care unit.1,2
Where can I get further information?
Make sure you contact your GP or travel health practitioner in plenty of time before you travel to discuss the ways you can help to keep yourself healthy whilst away. You should try and contact them at least 4–6 weeks before your trip.
After your trip, you should contact your GP if you develop a fever or notice any other unusual symptoms.
The information provided is a summary that was up to date when this article was published; however, recommendations may be updated from time to time. Please always consult with your doctor, nurse or pharmacist well in advance of travelling.
References
1. Fit For Travel. Japanese Encephalitis. Available at: http://www.fitfortravel.nhs.uk/advice/disease-prevention-advice/japanese-encephalitis.aspx. Accessed February 2024. 2. Travel Health Pro. Japanese Encephalitis. Available at: https://travelhealthpro.org.uk/factsheet/55/japanese-encephalitis. Accessed February 2024.
MAT-XU-2203074(v2.0) | February 2024
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