Japanese encephalitis (JE) is a rare but serious disease caused by the Japanese encephalitis virus (JEV). It is spread to humans by infected mosquitoes.
Less than 1% of people infected with JEV will experience symptoms. Some infected people experience an illness with fever and headache. People with a severe infection may experience neck stiffness, disorientation, tremors, coma and seizures. If you have any of these symptoms, seek medical treatment. Among those who develop severe infection, some will go on to experience permanent neurological complications or possibly death.
Symptoms, if they are to occur, usually develop 5 to 15 days after being bitten by infected mosquitoes.
JE is spread by the bite of infected Culex species mosquitoes which are commonly found in NSW. Culex mosquitoes can become infected with JEV from biting infected animals.
The virus is spread when mosquitoes bite an infected animal and the mosquito then bites a human. Infected pigs and some waterbirds are the animals more likely to infect mosquitoes.
Humans are not able to pass JEV to other humans. Humans cannot get infected with JEV by touching an infected animal or eating animal products including pork or poultry products.
JEV has recently been identified in commercial piggeries in locations in NSW, Queensland, Victoria and South Australia. NSW Health is working to better understand the full extent of JEV in NSW. Local infection risks in NSW are likely highest among:
JEV is endemic in much of Asia and parts of the Pacific. For most travellers in these regions, the risk of being infected with JEV is very low. People at the greatest risk of becoming infected are those who are staying more than a month in rural areas in countries where the disease is endemic or in some of the Torres Strait Islands.
The mosquitoes that transmit JEV are most active at dawn and dusk and into the evening. Take extra care during peak mosquito biting hours, avoid the outdoors if possible or take preventive actions.
A safe and effective vaccine for JE is available for people aged 2 months and older.
Vaccination against JE is currently only recommended for those at highest risk of infection. Se section Who is at risk?
JEV infection is usually diagnosed from measuring levels of antibodies to JEV in samples of blood or spinal fluid. If you have been infected, you do not put others at risk.
If you have symptoms consistent with JE seek medical treatment.
If you have any severe signs such as headache, vomiting, confusion, paralysis or seizures you should call 000 immediately.
There is no specific treatment available for JE. The best way to avoid infection is to avoid being bitten by mosquitoes.