Japanese encephalitis Vaccination

Japanese encephalitis is a mosquito-borne flavivirus that can result in permanent neurological damage. mosquitoes can pick up the virus from infected birds or animals, and then bite you and pass it on.

Most cases are mild, but one in 250 progresses to a severe clinical case; and about 30 per cent of these patients will die. The World Health Organization records 68,000 clinical cases of JE every year.

Symptoms of Japanese encephalitis

Five to fifteen days after being bitten by an infected mosquito the patient suffers a flu-like illness, although many people with JE show no symptoms. If you are travelling or have just returned from travelling, particularly in the tropics, any flu-like illness is a cause for concern and you should seek medical advice and tell your healthcare professional where you have visited.

About one in 250 cases of JE progress to encephalitis (swelling of the brain) convulsions, headaches, paralysis and neck stiffness can accompany a high fever. One in three patients who progress to this stage will die.

Countries where Japanese encephalitis is a risk

This disease occurs in South East Asia and in the Indian subcontinent and is contracted by a bite from an infected mosquito. Cases have been seen in the Western Pacific islands, Pakistan, the north coast of Australia and even parts of Russia. The US Centres for Disease Control has a map showing the distribution of JE. It is rare in Japan, however, because of an immunisation programme.

The relevant species of mosquito breeds in rice paddies.

Which travellers are at risk from Japanese encephalitis?

Your risk of being bitten by a mosquito carrying JE is elevated if you are visiting a high-risk area during the rainy season or if you will be staying near rice paddies, pig farms or marshland. Anyone engaging in outdoor activities, for example, cycling and camping, in a high-risk area should also take precautions. If you want more in-depth advice about how to protect yourself from JE, make an appointment at Global Travel Clinics.

Prevention of Japanese encephalitis

Vaccination against JE will give you a degree of protection, and we can help you with that at Global Travel Clinics – but you need to back that up by avoiding mosquito bites. The mosquito that carries JE is active at dusk and prefers humid conditions. You can protect yourself from mosquito bites by:

• using good quality insect repellents on exposed skin, opt for insect repellents that contain DEET or dimethyl phthalate or eucalyptus oil
• treat your sleeping space with insecticide before you turn in for the night
• sleep in rooms with screens, or under nets if you are outside
• cover up with loose clothing, including long-sleeved tops, trousers and socks

JE infections are more common during the rainy season. The Met Office has a list of countries with their rainy seasons.

See our blogpost for more information about avoiding mosquito bites.