Mosquito Madness: Japan Encephalitis Warning Issued in South Korea

A nationwide alert has been issued for Japanese encephalitis.

The Korea Disease Control and Prevention Agency (KDCA) announced yesterday that a nationwide alert for Japanese encephalitis has been issued. This alert was prompted by the confirmation that over 50% of mosquitoes collected in Gyeongsangnam-do and Jeollanam-do, South Korea, were Culex tritaeniorhynchus, the vector for Japanese encephalitis.

KDCA issues a Japanese encephalitis alert when more than 50% of mosquitoes collected in specific regions are confirmed to be Culex tritaeniorhynchus, the primary carrier of the Japanese encephalitis virus.

According to surveillance results, Culex tritaeniorhynchus mosquitoes constituted 63.2% (2,456 out of 3,884 mosquitoes) in Gyeongnam and 58.4% (1,684 out of 2,878 mosquitoes) in Jeonnam.

KDCA reported that this year’s Japanese encephalitis alert was issued on the same date as in 2023. There have been no reported cases of Japanese encephalitis in the country so far this year. In 2023, the first case was reported on September 6, leading to 17 cases and 2 fatalities.

An analysis of the 91 reported cases of Japanese encephalitis from 2019 to 2023 shows that individuals aged 50 and older accounted for 87.9% (80 people) of the total cases, with the highest occurrence reported in Gyeonggi, Seoul, and Gangwon provinces in South Korea.

Japanese encephalitis virus infection typically manifests with mild symptoms like fever and headaches. However, in rare cases, it can progress to encephalitis, marked by high fever, seizures, neck stiffness, confusion, convulsions, and paralysis, with a mortality rate of 20 to 30%. Notably, even after recovering from encephalitis, 30 to 50% of patients may experience various neurological complications depending on the affected brain regions.

KDCA emphasized the availability of an effective vaccine against Japanese encephalitis and encouraged eligible individuals born after 2011 to adhere to the standard vaccination schedule. They also recommended vaccinations for residents in high-risk areas such as rice paddies and pig farms and travelers visiting countries where Japanese encephalitis is prevalent.