Japanese Encephalitis

Learn more about Japanese Encephalitis (JE) and how you can protect yourself and others when you travel. We explain how you get Japanese Encephalitis, the symptoms and how you can prevent the disease.

What is Japanese Encephalitis?

Japanese Encephalitis is a viral disease spread through mosquito bites and it is found throughout Asia and the Western Pacific areas, not just in Japan!

Fact: In 1871 the first documented case of this disease was recorded in Japan, hence the name Japanese Encephalitis.

Structurally similar to Dengue Fever, Yellow Fever and West Nile virus this disease causes an estimated 68000 symptomatic cases every year and although rare the impact of the disease is profound. Typically around 30% of symptomatic individuals will die, with another 30% suffering permanent limb paralysis (quadriplegia). The rest will likely suffer from intellectual or behavioural changes like the inability to speak. After effects like these emphasise the profound impact this disease has on the populations of these regions with JE being the most important cause of viral encephalitis (life-threatening swelling of the brain) in Asia.

Initial symptoms occur within 4-14 days and usually present with a high fever, headache, vomiting and stomach pain. Symptoms can rapidly progress to seizures, paralysis, coma and then death.

How do you get Japanese Encephalitis?

Japanese Encephalitis is spread through the bite of an infected mosquito, typically the Culex species, and cannot be transmitted human to human, or even human to mosquito to human. This is because levels of virus in humans are usually too low for onward transmission. The typical transmission cycle involves pigs and/or water birds who host the virus with onward transmission to humans after being bitten by an infected mosquito.

Why am I at risk of getting Japanese Encephalitis?

Japanese Encephalitis vaccination is not part of the childhood immunisation programme in the UK so you will have no immunity to this disease. Travelling to areas of the world typically rural areas where JE can be found will increase your risk of contracting this disease. Other risks include the length of stay, with longer stays in risk areas increasing the odds of encountering the disease.

Typically the disease is found in rural locations where agriculture (rice fields) and farming (pigs) occur, however, any stagnant water can become a breeding ground for mosquitoes meaning this disease can proliferate in urban locations. JE outbreaks occur every 2-15years and transmission risk intensifies during the rainy season.

Mosquito bites can very difficult to avoid and it only takes one bite from an infected mosquito to cause JE as well as many other infectious diseases, for example, dengue fever and malaria. Keep reading to learn more about bite avoidance techniques.

How can I prevent Japanese Encephalitis?

Vaccination is the best method of prevention but bite avoidance should also be practised to reduce the risk of Japanese B Encephalitis as well as other diseases spread by mosquitoes and biting insects. Whilst the risk of contracting the virus is low, the impact is high enough that the vast majority of Asian countries vaccinate their population against the disease.

Bite avoidance: Typically insect repellents containing 50% DEET and long loose-fitting clothing are the best methods of avoiding bites during waking hours. When sleeping always use a mosquito net, make sure windows are doors are properly screened, and if available use air conditioning. More about insect bite avoidance can be found at Travel Health Pro.

Ixiaro, the Japanese Encephalitis Vaccine

Vaccination with Ixiaro is the best method of preventing the disease if travelling to risk areas like Asia and the Western Pacific.

There are no specific treatments for patients who contract the disease.

Ixiaro is an inactivated vaccine, this means that the injection cannot give you Japanese Encephalitis but will trigger your immune system into making antibodies.

A primary course of Ixiaro consists of 2 doses. The first 2 doses are administered around 1 month apart prior to travel to a risk area and it can be safely used in children, adults and the elderly.


Not got 1 month to spare before travel? Don’t worry as there are accelerated schedules of Ixiaro suitable for adults (18-65 years old) that can rapidly protect you against Japanese Encephalitis in just 7 days.


Booster doses of this vaccine are recommended if travelling into risk areas again. The 1st booster is usually given 12-24 months after the primary course, with top-ups every 10 years thereafter.

What side effects could I expect from a Japanese Encephalitis vaccine?

As mentioned earlier Ixiaro vaccines are safe and effective; adverse events are infrequent. Inactivated vaccines like Ixiaro cannot cause the disease that we are attempting to protect you against. In this respect, they are just like the flu vaccine which should also be considered a travel vaccine depending on the season you are travelling. Typical adverse events are usually limited to:

  • Injection site reactions like a sore arm or redness swelling or tenderness at the injection site
  • Low-grade fever (greater than 37.5C)
  • Fatigue and Tiredness

These symptoms will usually resolve within a few days and require only paracetamol or a cold compress (if swelling at the injection site) to manage them. A full list of adverse vents can be found in the Patient Information Leaflet.

Can I get a Japanese Encephalitis vaccine free from my doctor?

No. Japanese Encephalitis vaccines are not provided free of charge on the NHS for travellers, they are a private service.

The pharmacists who manage our Peak Pharmacy travel clinics will always tell you what vaccines you can obtain free of charge on the NHS, but for your information, these are usually TyphoidTetanus / Diphtheria / PolioHepatitis A and Cholera