There are signs that influenza (the flu) will spread about a month earlier than usual. In particular, the number of patients is rising quickly among elementary school students as the new term begins. COVID-19 has also increased for six consecutive weeks recently, putting respiratory infectious disease control on high alert ahead of the Chuseok holiday.
The Korea Disease Control and Prevention Agency held a joint task force meeting on respiratory infectious diseases with related ministries on the 8th to review domestic and overseas trends in influenza and COVID-19, vaccination plans, and the status of treatment supplies.
In week 35 of the last season (Aug. 23–29), the rate of influenza-like illness was 13.3 per 1,000 outpatients. That was a sharp rise from 9.2 the previous week and high compared with the same period in previous years. In week 35 last year, the rate was 6.4.
An influenza-like illness refers to a person with a fever of 38 C or higher and a cough or sore throat.
As patients increased, inpatients at hospital-level medical institutions also rose from 43 in week 32 to 162 in week 35. Influenza patients visiting emergency rooms increased more than fourfold over the same period, from 373 to 1,606.
By age, elementary school students showed the highest incidence. The rate of influenza-like illness among those ages 7–12 was 36.5 per 1,000 outpatients, higher than ages 1–6 (22.6) and 13–18 (14.6).
Considering the recent upward trend, the Korea Disease Control and Prevention Agency expects that in week 36, the first week of this season (Aug. 30–Sept. 5), the rate of influenza-like illness will exceed the threshold for issuing a warning. A warning is likely to be issued this week.
The virus detection rate is also rising. In week 35, the influenza virus detection rate was 12.3%, up from 10.0% the previous week. Compared with the same period in 2023 (4.2%), 2024 (1.3%), and 2025 (1.1%), it is much higher.
The virus mainly detected domestically now is influenza A (H1N1)pdm09. The Korea Disease Control and Prevention Agency said it shows high neutralizing activity against this season's vaccine strains, so vaccination is expected to be effective. No antiviral resistance gene mutations have been identified, so it can be treated with antivirals, the agency explained.
Influenza is also spreading faster overseas. In Japan, the number of influenza patients reported per medical institution in week 35 was 1.76, exceeding the epidemic threshold of 1.0. That is about five times higher than 0.35 in the same period a year earlier. Since influenza sentinel surveillance began in 1999 in Japan, this is the earliest level except during the 2009 H1N1 pandemic.
In China, influenza cases are also increasing, mainly in the south. In week 35, the positivity rate among hospital outpatients and emergency room patients was 17.7%, up from 16.4% the previous week.
Based on domestic and overseas trends, the Korea Disease Control and Prevention Agency projected that the scale of this season's influenza spread will be similar to last year. However, the duration of the spread could be longer.
COVID-19 is also on the rise. In week 35, COVID-19 inpatients numbered 109, fewer than 406 in the same period last year, but the figure has increased for six consecutive weeks, from 48 in week 32 to 57 in week 33, 61 in week 34, and 109 in week 35. The COVID-19 virus detection rate also rose to 11.7% in week 35, more than double from 5.7% four weeks earlier.
Considering the early influenza spread and the rise in COVID-19, the Korea Disease Control and Prevention Agency said it will proceed without delay with vaccinations for high-risk groups.
Influenza vaccinations will begin on Sept. 21 for children ages 6 months to 14 years and pregnant women. Starting on Sept. 28, they will expand to children who need only one dose. From Oct. 12, people 65 and older can receive influenza and COVID-19 vaccines together.
The Korea Disease Control and Prevention Agency said it also plans to review the supply of treatments such as antivirals and fever reducers and pain relievers with related ministries.
The Korea Disease Control and Prevention Agency asked the public to follow basic respiratory infection precautions, such as covering the mouth and nose with a tissue or sleeve when coughing or sneezing and washing hands. If influenza symptoms such as fever appear, people should refrain from going to work or school and get rest. In particular, for high-risk groups such as older adults, it is important to seek care quickly if symptoms appear.