The Korea Disease Control and Prevention Agency (KCDC) issued a nationwide Japanese encephalitis alert effective March 20 after the first sighting of the Japanese encephalitis-carrying Bug tritaeniorhynchus in Jeju Special Self-Governing Province on March 20.
Japanese encephalitis (JE) is a mosquito-borne infectious disease that occurs mainly in South Asia and the Western Pacific region. The main vector mosquito is Bug tritaeniorhynchuswhich is distributed nationwide.
Due to climate change, the timing of the emergence of vector mosquitoes is continuously being advanced, so this year surveillance began one week earlier than last year.
In just two days, a total of 18 mosquitoes were collected, and among them, one Japanese encephalitis vector mosquito was identified.
The average temperature in Jeju Special Self-Governing Province, where Japanese encephalitis vector mosquitoes were collected this year (February 16 to March 15), was 0.8℃ higher than last year, and the average maximum temperature was 12.5℃, an increase of 1.1℃ compared to last year, so it is estimated that the appearance of mosquitoes has become earlier.
Podcast: Japanese encephalitis with Dr. Melvin Sanicas
The Korea Disease Control and Prevention Agency has been monitoring the occurrence of vector mosquitoes and pathogen infection since 1975 to prevent Japanese encephalitis infection. Japanese encephalitis vector mosquitoes begin to appear in late March and reach their peak in August or September.
The number of Japanese encephalitis patients in Korea averaged around 17.4, with the first patient typically reported in August or September and continuing until November. Looking at the characteristics of patients reported for Japanese encephalitis over the past five years (79 cases), men accounted for 60.8%, which was higher than women, and 65.9% of the total patients were over 50 years old.
Initial symptoms of Japanese encephalitis are mild, such as fever, headache, and vomiting; however, if it progresses to encephalitis in rare cases, symptoms such as high fever, seizures, confusion, convulsions, paralysis, and disorientation may appear, and 20 to 30% of patients may die. In particular, even after recovery from encephalitis, 30 to 50% of patients may experience various neurological complications depending on the site of injury.
Since an effective vaccine for Japanese encephalitis is available, it is recommended that children eligible for the national immunization program (those born after 2013) be vaccinated according to the standard immunization schedule.
In addition, vaccination (at a cost) is recommended for adults aged 18 or older who have no prior experience with Japanese encephalitis vaccination, including ➊ those who live in a risk area (near rice paddies or pig farms) or plan to be active in a risk area during the transmission season, ➋ foreigners who have migrated from a non-endemic area and will reside in the country for a long period, and ➌ travelers to countries at risk of Japanese encephalitis*.
* Countries at risk of Japanese encephalitis: Bangladesh, Bhutan, India, Nepal, Pakistan, Sri Lanka, Brunei, Myanmar, Cambodia, Indonesia, Laos, Malaysia, Philippines, Singapore, Thailand, East Timor, Vietnam, China, Japan, North Korea, South Korea, Taiwan, Russia, Australia, Papua New Guinea, etc. (CDC, June 2025)
Lim Seung-kwan, Commissioner of the Korea Disease Control and Prevention Agency, urged the public to observe mosquito bite prevention guidelines as the activity of Japanese encephalitis-carrying mosquitoes begins in earnest, and emphasized that children eligible for the national mandatory vaccination program must ensure they receive their vaccinations.
In addition, it was emphasized that “each local government should establish control plans, such as carefully identifying vulnerable areas like those with high mosquito larval outbreaks, and manage the situation thoroughly to minimize patient occurrences by lowering the density of vector mosquitoes through comprehensive control.”