On 9 September 2026 the Korea Disease Control and Prevention Agency (KDCA) confirmed this year’s first Japanese encephalitis patient — a woman in her 60s with no vaccination history. This year’s warning was issued on 17 June, the earliest in ten years. Japanese encephalitis usually passes mildly but is dangerous if it progresses to encephalitis, and above all it is a disease with an effective vaccine. We reproduce the release’s ten-year table and vaccination schedule and add figures we worked out from the table.
1. 80% of cases fall in September and October. Most Korean cases occur between August and November, with 80% in September and October, and 65.9% are aged 50 or over.
2. If it becomes encephalitis, 20–30% may die. Infection usually means only fever and headache, but in rare progression to encephalitis 20–30% may die and 30–50% may suffer neurological complications.
3. Children 12 and under are vaccinated free. Those born from January 2013 are covered by the national programme, and unvaccinated adults living near rice paddies or pig farms or travelling to risk countries are advised to get a paid vaccination.
The last ten years — the release’s table
| Year | Warning issued | Cases (deaths) |
|---|---|---|
| 2017 | 29 June | 9 (2) |
| 2018 | 6 July | 17 (1) |
| 2019 | 22 July | 34 (6) |
| 2020 | 23 July | 7 (2) |
| 2021 | 5 August | 23 (5) |
| 2022 | 23 July | 11 (0) |
| 2023 | 27 July | 17 (2) |
| 2024 | 25 July | 21 (6) |
| 2025 | 1 August | 7 (0) |
| 2026 | 17 June | 1 (provisional, as of 9 September) |
The release’s table also gives advisory dates and first-case dates; for 2026 the advisory was 20 March and the first case was confirmed on 9 September. The row layout is ours.
We worked out two things from the table. First, ranking the ten warning dates puts 17 June 2026 earliest, followed by 29 June 2017. Second, the nine completed years 2017–2025 add up to 146 cases and 24 deaths, a death share among reported cases of about 16.4%. Reported cases are mostly people ill enough to be diagnosed, so read this with care — it is not the death rate among everyone infected.
Symptoms — mild at first
The release says infection with Japanese encephalitis virus brings mild symptoms such as fever and headache, but rare progression to encephalitis causes high fever, seizures, neck stiffness, confusion, convulsions and paralysis. This year’s patient went to hospital with a fever of 39.1°C, chills and vomiting. The KDCA’s advice is to seek care promptly if such symptoms follow activities where mosquito bites were likely.
The mosquito — Culex tritaeniorhynchus, biting at night
The vector, Culex tritaeniorhynchus, is a small dark-brown mosquito that feeds mainly at night and is active nationwide from April to October. As of early September (week 36) the average mosquito index was 121, and they were still being caught.
- From April to October, limit outdoor activity from just after sunset to just before sunrise
- At night, wear loose, light-coloured long clothes and apply repellent to exposed skin, clothes, shoe tops and socks
- Avoid strong perfumes and cosmetics
- Fix window screens, use mosquito nets, and remove standing water such as puddles and blocked drains
Vaccination — two vaccines, not to be mixed
| Vaccine | Doses | Schedule |
|---|---|---|
| Inactivated | 5 in total | Doses 1 and 2 at 12–23 months, 1 month apart; dose 3 11 months after dose 2; doses 4 and 5 at ages 6 and 12 |
| Live | 2 in total | Dose 1 at 12–23 months; dose 2 12 months later |
Switching between live and inactivated vaccines is not accepted — finish with the vaccine you started. The national programme covers children aged 12 and under (born from January 2013).
What about adults? For adults 18 and over with no past vaccination, a paid vaccination is recommended if they (1) live near rice paddies or pig farms or will be active there during the transmission season, (2) are foreigners from non-endemic areas settling long-term in Korea, or (3) are travelling to a risk country. The risk-country list the release quotes from the US CDC (June 2025) has 25 countries, including China, Japan, Vietnam, Thailand, the Philippines, India, Indonesia, Taiwan, Australia and Russia — and South Korea itself.
Checklist
- ☐ Your child’s record — with the inactivated vaccine, were the boosters at 6 and 12 done?
- ☐ Unvaccinated adults living near paddies or farms — ask about paid vaccination
- ☐ Before long trips to Southeast Asia, China and similar — check vaccination
- ☐ Until October, cut down on outdoor time after dark and check screens
Questions that remain
I was bitten by a mosquito — should I worry?
The release says most infections stay mild. Rather than the bite itself, watch for later high fever, headache, vomiting or changes in consciousness, and seek care straight away if they appear.
Is it different from the autumn illness caught in grass?
Yes. Scrub typhus, caught in autumn grass, is spread by chigger larvae and peaks in October and November; its release gives no vaccine option, so avoiding bites and early treatment are the key.
What if I fall ill abroad?
Handling emergencies while travelling is covered in travel emergencies.
Sources
- KDCA press release — “First Japanese encephalitis patient this year: follow prevention rules and get vaccinated” (9 September 2026, last revised 17 September; checked 29 September 2026). Source for the ten-year table, the first patient (woman in her 60s, unvaccinated), 80% in September–October and 65.9% aged 50+, 20–30% deaths and 30–50% complications, the vector and a mosquito index of 121, the vaccination schedules and no switching, adult recommendations and the risk-country list, and the prevention rules.
- Our own working. The ranking of warning dates, the 2017–2025 totals of 146 and 24, and 16.4% are our arithmetic from the release’s table.
Where to check further
- Your child’s record and free vaccination sites — the KDCA vaccination helper service.
- Paid adult vaccination — a nearby clinic.
Written on 29 September 2026. Figures and schedules are from the KDCA release as written; the tables and arithmetic are ours. This article is not a substitute for medical care. This autumn’s flu vaccination schedule is in 2026 flu vaccination.
