South Korea has confirmed its first Japanese encephalitis case of the year. Most infections cause only mild symptoms, but some progress to encephalitis, which can lead to death or neurological complications. The Korea Disease Control and Prevention Agency urged the public to limit outdoor activity at night and avoid mosquito bites ahead of September and October, when cases are concentrated.
The first patient this year is a woman in her 60s, the agency said on the 11th. She visited a medical facility on the 15th of last month with fever, chills and vomiting. Agency testing found that antibody levels in her convalescent serum were more than four times higher than during the acute phase, and she was diagnosed on the same day. An epidemiological investigation confirmed that she was infected after being bitten by a mosquito and had no record of vaccination against the disease.
Most Cases Occur From August to November, With 80% in September and October
Cases in South Korea occur mainly between August and November. About 80% of all patients are reported from September through October, making the next two months a period requiring particular caution. By age, patients aged 50 and over account for 65.9% of the total.
Infection with the Japanese encephalitis virus typically produces relatively mild symptoms such as fever and headache. In rare cases, however, it progresses to encephalitis, bringing severe symptoms including high fever, seizures, neck stiffness, confusion, convulsions and paralysis. Of those cases, 20% to 30% can be fatal. Between 30% and 50% of patients who develop encephalitis experience neurological complications that vary by the area of damage, making prompt diagnosis and treatment critical.
The Culex tritaeniorhynchus mosquito that carries the virus is small and dark brown. It feeds on human blood mainly at night and is active nationwide from April through October. It breeds in rice paddies, livestock sheds and puddles, and its feeding activity intensifies in the evening hours.
The agency stressed that reducing outdoor activity at night and avoiding mosquito bites are the most important preventive steps. When going outside, people should wear light-colored, long or loose-fitting clothing and avoid strong perfumes or cosmetics that can attract mosquitoes.
Vaccination also matters. The agency recommends the Japanese encephalitis vaccine for children aged 12 and under, who are covered by the national immunization program. Adults who have never been vaccinated are advised to obtain the vaccine at their own expense if they live in or plan to spend time in high-risk areas. Vaccination is also recommended for foreign nationals moving to South Korea for long-term residence from non-endemic areas, as well as for people planning to travel to countries where the disease poses a risk.
"Patients are concentrated from September onward," agency Commissioner Lim Seung-kwan said. "Please follow preventive guidelines to avoid mosquito bites during outdoor activities."
