▲ Culex tritaeniorhynchus

On March 22nd, the Korea Disease Control and Prevention Agency (KDCA) issued an advisory against Japanese encephalitis throughout the nation as the first Culex tritaeniorhynchus—the vector mosquitoes of Japanese encephalitis—of the year were identified in Jeju.

Most people who are bitten by the vector mosquitoes carrying the Japanese encephalitis virus are asymptomatic. However, it requires caution as it can lead to fatal acute encephalitis in rare cases. There were seven Japanese encephalitis patients in Korea last year, and one of them passed away.

The Culex tritaeniorhynchus mosquito is dark brown and has no distinct pattern. There is a wide white band in the middle of the mouth, and the length is about 4.5mm. The population of these mosquitoes starts to increase in southern regions such as Jeju, Busan, and Gyeongnam in June and is soon spread nationwide. They can be observed in Korea until the end of October.

KDCA recommended that children 12 months to 12 years of age be vaccinated. As for adults, vaccination is recommended for those who live near areas with high vector mosquito population, such as rice paddies or pig farms, or plan to travel to countries with the Japanese encephalitis epidemic.

The Korea Disease Control and Prevention Agency issues an advisory every year when the vector mosquito that carries Japanese encephalitis is first identified. The announcements were made on April 8 in 2019, March 26 in 2020, and March 22 this year—arriving early each year due to factors such as climate change. KDCA hypothesizes that because the average temperature in Jeju this year is 1.34 degrees higher than the average of previous years, mosquitoes that survived the winter may have started activities earlier, hastening the timing of the Japanese encephalitis advisory.