Japanese encephalitis is a mosquito-borne viral infection found mainly in rural Asia and the western Pacific. Most infections cause no symptoms, but in rare cases the virus can inflame the brain, leading to serious and sometimes lasting illness. Travellers reduce their risk through mosquito-bite avoidance and, where appropriate, the Ixiaro vaccine available at Crewe Travel Clinic.
How it spreads
Through the bite of infected Culex mosquitoes, which bite mainly from dusk through the night in rural farming areas. It is not passed from person to person.
Where it occurs
Across rural and agricultural parts of South and South East Asia, the Indian subcontinent and the western Pacific, especially near rice fields, marshland and pig farming.
Main symptoms
Most infections are symptomless or mild. The rare severe form causes high fever, headache, confusion, seizures and, in some cases, coma.
Who is most at risk
Travellers spending longer periods in rural areas, those visiting during or just after the rainy season, and people with extensive outdoor or agricultural exposure.
Is a vaccine available
Yes. The inactivated Ixiaro vaccine is given as a two-dose course and is available at Crewe Travel Clinic.
How to reduce your risk
Avoid mosquito bites with repellent, covering up in the evening and a bed net, and have the vaccine where the risk justifies it.
Japanese encephalitis is a serious mosquito-borne viral brain infection found mainly in rural and agricultural parts of Asia and the western Pacific. Most infections are mild or symptomless, but a small number cause potentially life-threatening inflammation of the brain. Travellers avoid it by preventing mosquito bites (repellent, covering up and bed nets in the evening) and, where the risk warrants it, with the two-dose Ixiaro vaccine. Crewe Travel Clinic in Crewe, Cheshire offers Japanese encephalitis vaccination and personalised travel health advice.
Japanese encephalitis (JE) is a viral infection of the brain caused by the Japanese encephalitis virus, a flavivirus related to the viruses that cause dengue and yellow fever. It is spread to people through the bite of infected mosquitoes and is the leading cause of viral encephalitis across much of Asia. The virus circulates between mosquitoes, water birds and pigs, with humans only becoming infected by chance; people cannot pass the infection on to one another.
The great majority of those who are infected develop no symptoms at all, or only a mild, flu-like illness. However, in a small proportion of cases the virus crosses into the brain and causes encephalitis (inflammation of the brain). This severe form is uncommon but serious: it can be life-threatening and may leave survivors with long-term neurological problems. Because there is no specific antiviral treatment, care is limited to supporting the patient in hospital, which makes prevention especially important.
For most short-stay holidaymakers visiting cities and standard tourist destinations, the risk of Japanese encephalitis is very low. The risk rises with longer stays, rural and agricultural travel, and trips during or shortly after the rainy season. At Crewe Travel Clinic in Cheshire, a travel health nurse can assess your destination, the length and style of your trip, the season of travel and your planned activities, and advise whether bite avoidance alone is enough or whether vaccination is also recommended.
Japanese encephalitis is transmitted through the bite of infected Culex mosquitoes, which breed in standing water such as flooded rice paddies, marshes and irrigation channels. These mosquitoes typically bite from dusk through the night and are most active outdoors in rural farming areas. The virus is maintained in a cycle between mosquitoes and animals, particularly water birds and pigs, which act as amplifying hosts; this is why risk is often highest near pig farming and rice cultivation. Humans are an incidental, dead-end host, so the infection is not spread directly from person to person, nor through food, water or casual contact.
Most people infected with the Japanese encephalitis virus have no symptoms or only a brief, mild illness with fever and headache. When the more serious form develops, symptoms usually appear around 5 to 15 days after the infected mosquito bite and may begin with high fever, headache, nausea and vomiting. As the brain becomes inflamed, signs can progress to neck stiffness, confusion, disorientation, tremors or other abnormal movements, seizures and, in severe cases, coma. Severe Japanese encephalitis can be fatal, and a significant proportion of those who survive the brain inflammation are left with lasting neurological problems such as weakness, movement disorders, seizures or difficulties with thinking and behaviour. Anyone who develops a fever with severe headache, confusion or fits during or after travel to an affected area should seek urgent medical attention.
Japanese encephalitis occurs across South and South East Asia, the Indian subcontinent and parts of the western Pacific. Affected areas include India, Nepal, Sri Lanka, Bangladesh, China, Thailand, Vietnam, Cambodia, Laos, Myanmar, Malaysia, Indonesia, the Philippines, Japan, Korea, Taiwan and parts of Papua New Guinea and northern Australia (the Torres Strait). Risk is greatest in rural and agricultural settings, especially around rice fields, marshland and pig rearing. In tropical regions transmission can occur year-round, while in temperate areas it tends to peak in the warmer, wetter months. The risk to most urban and short-stay travellers is low.
There is no specific treatment for Japanese encephalitis, so prevention focuses on avoiding mosquito bites and, where the risk justifies it, vaccination. Because the Culex mosquitoes that carry JE bite mainly from dusk onwards, bite avoidance is the cornerstone of protection: use an insect repellent containing DEET (around 50%) on exposed skin, cover up with long sleeves and trousers in the evening, sleep under a mosquito net (ideally insecticide-treated) where rooms are not screened or air-conditioned, and consider treating clothing with permethrin. These measures also help protect against other mosquito-borne infections such as dengue and malaria. A safe and effective vaccine is available. Ixiaro is an inactivated Japanese encephalitis vaccine given as a two-dose course, with the doses normally 28 days apart and the course ideally completed at least one week before travel; an accelerated schedule may be possible for adults who are short of time. Vaccination is generally recommended for travellers spending longer periods (often a month or more) in rural or agricultural areas of affected countries, those travelling during or just after the rainy season, people making repeated or long-stay trips, and anyone planning extensive outdoor activity near rice paddies, marshland or pig farming. At Crewe Travel Clinic in Crewe, Cheshire, your travel health nurse will assess your itinerary and advise whether the Ixiaro vaccine is appropriate for you.
Japanese encephalitis is spread by infected Culex mosquitoes, which breed in standing water such as flooded rice paddies, marshes and irrigation channels. These mosquitoes bite mainly from dusk through the night and are most active outdoors in rural farming areas. The virus is maintained in a cycle between mosquitoes and animals, particularly pigs and water birds, which act as amplifying hosts. People are an incidental, dead-end host, so the infection cannot be passed from one person to another.
Because there is no specific treatment, prevention is centred on avoiding mosquito bites and, where the risk justifies it, vaccination. As the mosquitoes that carry the virus bite mainly from dusk onwards, evening and night-time bite avoidance is especially important. These measures also help protect against other mosquito-borne infections such as dengue and malaria.
Most people infected have no symptoms or only a mild, flu-like illness. When the serious form develops, symptoms usually appear around 5 to 15 days after the bite and can progress rapidly as the brain becomes inflamed. As there is no specific antiviral treatment, urgent hospital care is needed for the severe form.
A safe and effective vaccine is available. Ixiaro is an inactivated Japanese encephalitis vaccine given as a two-dose course, with the doses normally 28 days apart and the course ideally completed at least one week before travel. An accelerated schedule may be possible for adults who are short of time. At Crewe Travel Clinic your travel health nurse will assess your itinerary and advise whether vaccination is appropriate for you.
The following vaccinations can help protect against Japanese Encephalitis.
Book an appointment with our travel health team for tailored advice on protecting against Japanese Encephalitis.