Japanese encephalitis in South Korea - the current situation

A case of Japanese encephalitis has been reported by The Korean Disease Control and Prevention Agency (KDCA). This is the first notification for the 2026 season. According to the report (September 9), the patient is in her 60s and was admitted to hospital in mid-August.

Most cases of Japanese encephalitis in South Korea are over 50 years of age and occur between August and November.

There have been 79 cases and 13 deaths in the last 5 years (2021-2025).

How South Korea's surveillance system works

No location was mentioned for the current case but a nationwide alert for Japanese encephalitis was issued during June this year.

Active surveillance of the mosquito responsible for transmitting the disease has been in place for over 50 years. An alert is issued if certain criteria are met. These include:

• if the daily average number of collected Culex tritaeniorhynchus mosquitoes is more than 500 or accounts for 50% or more of the total mosquito density
• if relevant virus genetic material is detected in mosquitoes
• if a case of Japanese encephalitis occurs

Virus genetic material was identified in mosquitoes in the Daegu region of South Korea in June. Daegu is in the south-eastern region of South Korea.

Japanese encephalitis is a notifiable disease in South Korea.

Vaccination has been free for children born after 1 January 2012. It is part of their childhood national immunisation program. It is also recommended for those over the age of 18 years who live in areas of risk.

Japanese encephalitis (JEV) risk to international travellers

There are currently 24 countries in the South-East Asia and Western Pacific regions that have Japanese encephalitis transmission risk. More than 3 billion people live in endemic areas. The World Health Organization (WHO) states that major outbreaks of Japanese encephalitis occur every 2-15 years.

The incidence of JEV cases in Japan, Republic of Korea and some regions in China, Nepal, Sri Lanka, Thailand and Vietnam has declined in recent years, largely because of immunisation.

For most travellers to Asia and parts of the Western Pacific, the risk of Japanese encephalitis is low, particularly for short term visitors to urban areas. This risk is estimated to be less than 1 in a million per month of stay but will change according to season, destination, duration of travel and intended activities.

Environmental determinants of Japanese encephalitis prevalence include climate, rainfall, temperature, wind, water bodies, and the proximity to irrigation and pig farming.

Japanese encephalitis is most prevalent in rural or agricultural areas, often associated with rice farming, as the breeding grounds for the transmitting mosquito rely on an adequate supply of water. In temperate regions of Asia, transmission is seasonal, with peak cases of infection in the summer and autumn months. In the tropics and subtropics, transmission can occur year-round, peaking during the wet season.

Mosquito biting habits and prevention advice

Travellers to endemic areas should be reminded of the risk of mosquito-borne disease and individual mosquito biting habits. Mosquitoes transmitting Japanese encephalitis are most active at dusk and dawn and accommodation plays an important role in prevention with night-time biters.

Mosquito avoidance measures are very important at all times for all mosquito transmitted diseases.

Primary prevention always rests with mosquito avoidance measures. However, two excellent Japanese encephalitis vaccines are available in Australia (Imojev, Jespect).