people who work or do outside activities (e.g., camping, fishing, hiking, gardening) in high-risk areas. people working at and, or living close to piggeries (if infected by a mosquito, pigs can get high levels of virus, and infect more mosquitoes if bitten)
The people most at risk are those who live and work in rural areas, such as on pig farms and in rice fields, where the condition is widespread. Around 75% of cases involve children under the age of 15. Find out more about the causes of Japanese encephalitis, and which countries have the highest risk.
The chances of contracting Japanese encephalitis are small, at about 1 in a 1,000,000 chance. However, JE is a serious disease and once contracted, generally 1/3 of people will recover fully, 1/3 will have ongoing neurological issues and 1/3 will die from the disease.
Most people infected with JE do not have symptoms or have only mild symptoms. However, a small percentage of infected people develop inflammation of the brain (encephalitis), with symptoms including sudden onset of headache, high fever, disorientation, coma, tremors and convulsions. About 1 in 4 cases are fatal.
JE primarily affects children. Most adults in endemic countries have natural immunity after childhood infection, but individuals of any age may be affected.
It takes 5 to 15 days after the bite of an infected mosquito to develop symptoms.
About Japanese encephalitis
It is spread through bites from mosquitos, which become infected through biting infected pigs and waterbirds. JEV is endemic to parts of Asia and the Torres Strait region of Australia.
In persons who develop symptoms, the time from infection until illness onset (incubation period) is typically 5-15 days. Initial symptoms often include fever, headache, and vomiting. Mental status changes, neurologic symptoms, weakness, and movement disorders might develop over the next few days.
The Japanese encephalitis vaccine is not usually recommended for children less than 2 months old because it's unclear how safe and effective it is for this age group. You should not have the vaccine if you have had a severe allergic reaction (anaphylaxis) to it or any of its ingredients in the past.
Between 2012 and 2020, only 14 human JEV cases were notified to Australia's National Notifiable Disease Surveillance System, with all acquiring their infection overseas.
Fewer than 1% of Japanese encephalitis cases are believed to be symptomatic, leading researchers to estimate the number of overall cases to be in the thousands. For those developing symptoms, the fatality rate is estimated at around 30%, with around half of survivors said to have long-term neurological damage.
JEV vaccines are recommended for people at risk of exposure to the virus, as advised by your local public health authority. There are 2 JEV vaccines available and are registered for use in Australia: Imojev. JEspect (also known as Ixiaro).
Travelers to some parts of Asia and the Western Pacific can get infected if bitten by an infected mosquito. However, for most travelers the chance of getting infected with Japanese encephalitis virus is low.
Japanese encephalitis virus (JEV) is a flavivirus related to dengue, yellow fever, and West Nile viruses that can be spread by some (but not all) types of mosquitoes.
Only if you plan to visit rural areas for 4weeks or more, except under special circumstances, such as a known outbreak of Japanese Encephalitis. There is the risk of Dengue Fever & protecting yourself against insect bites (Mosquito) will help to prevent this disease.
Ninety percent of people with encephalitis have flu-like symptoms, such as fever, sore throat, cough, and malaise. If the person has meningitis and encephalitis, he or she may have a headache, stiff neck, vomiting, and be bothered by light.
The best way to prevent Japanese encephalitis virus infection is to protect yourself from mosquito bites. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and get vaccinated before traveling, if vaccination is recommended for you.
JE virus is transmitted to humans through the bite of infected Culex species mosquitoes, particularly Culex tritaeniorhynchus.
Diagnosing encephalitis
Early diagnosis is vital, as symptoms can appear suddenly and escalate to brain damage, hearing and/or speech loss, blindness, or even death.
Laboratory diagnosis of JE is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect virus-specific IgM antibodies. JE virus IgM antibodies are usually detectable 3 to 8 days after onset of illness and persist for 30 to 90 days, but longer persistence has been documented.
17.7% of 282 Acute encephalitis and complex febrile leisure patients in Bali were confirmed infected by JEV in which 92% of them were children under 15 years old.
These are also the first known locally-acquired detections of JE in humans in these states of Australia and the first detections in mainland Australia since a single case was detected in 1998 in Cape York, Queensland. JEV, which infects both humans and animals, has also been detected in animals in Australia.
IXIARO is given as a two-dose series, with the doses spaced 28 days apart. Adults aged 18–65 years can get the second dose as early as 7 days after the first dose. The last dose should be given at least 1 week before travel.