Japan MHLW Reports Unusually Early Start to the Fall Flu Season - South Korean CDC Flu Alert 9/11

[Michael Coston]

Japan MHLW Reports Unusually Early Start to the Fall Flu Season​

#19,312


Even though it is still August - and the Southern Hemisphere's flu season is still ongoing - Japan's Ministry of Health, Labour and Welfare today has announced an unusually early start to their fall flu season.




(translated)


While primarily a fall/winter phenomenon, the Northern Hemisphere isn't entirely devoid of influenza in the summer. Hong Kong often reports both a winter and a summer flu season and has been reporting elevated activity (mostly H1N1) since mid-summer.




Hong Kong's CHP also reported the following Mainland update in yesterday's weekly flu report:

In Chinese Mainland (week ending Aug 16, 2026), the percentage of specimens that tested positive for influenza in the southern provinces slightly increased, while that in the northern provinces remained low, with the rates at 18.6% and 2.1% in week 33, respectively. The proportion of influenza A(H3N2) among detections increased nationwide. In Macao (week ending Aug 15, 2026), the influenza positivity rate was 20.9%, which was higher than the alert level. Influenza A (H3) was predominating.

While Japan's flu season normally begins in November or December, last year it kicked off in early in early October, with the arrival of the drifted subclade K H3N2 virus.

While it is too soon to even begin to guess about the severity - or longevity - of this year's flu season, Japan is urging its citizens to take prevention seriously. The following (translated) excerpt comes from today's press release.

[Basic Infection Control Measures] Effective ways to prevent infectious diseases, including influenza, are "handwashing" and "cough etiquette , including wearing a mask ."

In particular, the risk of developing severe symptoms increases for the elderly and those with underlying medical conditions. When meeting with the elderly, going to the hospital, or gathering in large groups, please cooperate with infection control measures, including wearing a mask.

[Situations where wearing a mask is effective] To prevent infection among the elderly and other people at high risk of severe illness, wearing a mask is recommended when visiting a medical institution or when visiting medical institutions or elderly care facilities where many elderly people and other people at high risk of severe illness are hospitalized or living . In addition, during influenza season, when people at high risk of severe illness go to crowded places, wearing a mask is an effective measure to protect themselves from infection.

Attachment This outbreak is the second earliest since the Infectious Diseases Control Law was enacted in 1999, following 2009*, and last year...

[Vaccination] The influenza vaccine is believed to have some effect in suppressing the onset of the disease and preventing severe illness, and is considered to be particularly effective for the elderly and those with underlying medical conditions, who are at high risk of developing severe illness if they contract the disease. The following people are eligible for routine vaccination: ÿ People aged 65 and over ÿ People aged 60-64 with impaired heart, kidney, or respiratory function that severely restricts their daily life , or people with impaired immune function due to human immunodeficiency virus (HIV) that make daily life almost impossible. These people can receive one dose of influenza HA vaccine as part of routine vaccination. In addition, the influenza vaccine and the COVID-19 vaccine can be administered on the same day. Please consider getting vaccinated together with the COVID-19 vaccine. We would appreciate your cooperation in spreading this information to the media.

(Reference) Summer Infectious Disease Control Measures | Ministry of Health, Labour and Welfare Phone number: 0120-995-956 Reception hours: 9:00 AM - 5:00 PM, Monday to Friday (excluding public holidays and year-end/New Year holidays) According to the infectious disease surveillance data for the 34th week of 2026 (August 17th to August 23rd), the number of reported influenza cases per sentinel site was 1.11 (number of sentinel sites: approximately 3,000 nationwide, number of reported cases: 4,094).

Since this exceeds the threshold of 1.00 used as the benchmark for the start of an epidemic, it is believed that the influenza season has begun again this year. We have opened a consultation service for infectious diseases and vaccinations, including influenza . Please feel free to use it. *The telephone number changed on April 1, 2025

Every flu season is different, and as we've seen many times, flu seasons can vary widely around the world, making it unknowable if this early arrival will be duplicated in North America or Europe.

While I generally like to wait until October to get my seasonal flu shot, if this trend continues, I expect I'll be rolling up my sleeve a little earlier this year.



https://afludiary.blogspot.com/2026/08/japan-mhlw-reports-unusually-early.html

 

[Michael Coston]

South Korean CDC Issues Early Seasonal Flu Epidemic Advisory​

Proportion of Suspected Influenza Cases in Clinics
( As of Sep 5, 2026 ; Persons / 1,000 Persons )

#19,330

Typically, nations in the Northern Hemisphere don't even begin tracking seasonal influenza seriously until October 1st; the assumed start of each year's flu season. Our own CDC only publishes an abbreviated FluView report during the summer months (see Week 20 2026 notice below).




Two weeks ago (Aug 28th), however, Japan announced the earliest start since the 2009 H1N1 pandemic for their flu season (see Japan MHLW Reports Unusually Early Start to the Fall Flu Season), while Taiwan reported this week `. . . emergency room visits reached 11.2%, exceeding the epidemic threshold (11.0%), indicating the start of the epidemic period.'

Hong Kong - which often reports a biphasic flu season - continues to report a strong summer wave of influenza, and China reports elevated flu activity in their southern provinces for week 36.

This unusual wave of early flu continues, as today South Korea's CDC issued an early seasonal flu advisory, citing a 4x higher rate of ILI (Influenza-like Illness) consultations this week than a year ago.

(translation)

Influenza Epidemic Advisory Issued for 2026-2027 Season; Early Outbreak Compared to Previous Years, Response Strengthened for Students and High-Risk Groups (Fri, Sept. 11)

Date written 2026.09.11
Last modified date 2026.09.11
Department in charge Infectious Disease Control Division
contact 043-719-7141

Influenza Epidemic Advisory Issued for 2026-2027 Season; Early-than-usual Outbreak, Response Strengthened for Students and High-Risk Groups

- With the start of the season, “2026-2027 Season Influenza Epidemic Advisory Issued” starting September 11 (Fri)

- Although COVID-19 levels are lower than the same period last year, the number of hospitalized patients continues to increase

- Conducted a review of the epidemic status and response measures together with experts and relevant ministries

Emphasize wearing a mask when experiencing respiratory symptoms and urge adherence to preventive measures against respiratory infections, such as covering the mouth and nose with a tissue or sleeve when coughing; high-risk groups need to visit a medical institution early for appropriate treatment if they experience fever or respiratory symptoms.

The Korea Disease Control and Prevention Agency (Director Lim Seung-kwan) announced that, as the incidence of influenza is higher than in previous years, it held the "9th Meeting of the Inter-Ministerial Joint Task Force on Respiratory Infectious Diseases" with medical experts and relevant ministries (Ministry of Health and Welfare, Ministry of Food and Drug Safety, Ministry of Education) to review the current status of influenza and COVID-19 outbreaks and response measures, and issued an "Influenza Epidemic Advisory" starting at 00:00 on September 11 (Fri).

(Criteria for issuing an epidemic advisory for the '26-'27 season) Issued following expert consultation when the proportion of suspected influenza (ILI) cases exceeds the epidemic threshold for the relevant season and the influenza virus detection rate is 5% or higher.

※ Influenza-like illness (ILI): Cases where a cough or sore throat is present along with a fever of 38°C or higher

【 Current Status of Influenza and COVID-19 Outbreaks 】

According to the results of the sample surveillance of influenza-like illness (ILI) at clinics, the proportion of influenza-like illness cases in the 36th week of 2026 (Aug. 30–Sept. 5) was 25.3 per 1,000 outpatients, exceeding the epidemic threshold for this season (12.9) and rapidly increasing to a high level compared to the same period last year (6.6).

* (ILI rate over the last 4 weeks) Week 33 7.5 → Week 34 9.2 → Week 35 13.3 → Week 36 25.3

※ The influenza surveillance system operates from week 36 to week 35 of the following year (September to August of the following year) as a single season.

Incidence is increasing across all age groups, with a relatively high and rapid increase observed in the school-age and infant/child age groups, in the order of 7-12 years (75.1 people), 1-6 years (49.8 people), and 13-18 years (31.3 people).

* 7-12 years (75.1 people) > 1-6 years (49.8 people) > 13-18 years (31.3 people) > 0 years (24.0 people) > 19-49 years (23.5 people) > 50-64 years (11.8 people) > 65 years and older (8.8 people)

The number of inpatients at sample medical institutions at the hospital level in week 36 was 300, which is about double the number from last week (166) and shows a higher incidence compared to the same period last year (23 in week 36 of '25), and the age group of inpatients aged 65 or older accounts for the largest proportion at 60.0%.

* (Number of hospitalized patients in the last 4 weeks) Week 33: 78 → Week 34: 89 → Week 35: 166 → Week 36: 300

The detection rate of influenza viruses is also showing an increasing trend*, and the influenza virus currently in circulation is Type A (H1N1) pdm09, which is similar to the vaccine strain for this season** and has been confirmed to have no mutations affecting resistance to treatment.

* (Detection rate over the last 4 weeks) Week 33 5.4% → Week 34 10.0% → Week 35 12.3% → Week 36 16.3%
**The virus used to produce the influenza vaccine recommended by the World Health Organization (WHO)

(SNIP)

The Korea Disease Control and Prevention Agency plans to sequentially implement the national influenza vaccination program starting Monday, September 21, but it also plans to review measures to adjust the vaccination schedule, focusing on high-risk groups including immunocompromised individuals, by comprehensively considering the epidemic situation and vaccine supply schedule.

(Continue . . . )

Many countries won't begin to ramp up their fall flu vaccination campaigns until October (see UKHSA blog), and as cited above, South Korea's target date is still 10 days away.

Given that this year's fall flu vaccines have been updated to reflect recent antigenic changes observed in all 3 seasonal flu types (see WHO Recommendations for Influenza Vaccine Composition), community immunity against this fall's array of circulating flu viruses may be low.

Complicating matters, South Korea is also reporting low, but rising, rates of COVID infection:

In addition, the number of COVID-19 inpatients at hospital-level sample surveillance medical institutions in the 36th week of 2026 (Aug. 30–September 5) was 193, which is lower than the same period of the previous year (433 in the 36th week of 2025), but has been continuously increasing since August, and by age group, the elderly aged 65 or older accounted for the largest proportion at 65.3% of the total.

* (Number of hospitalized patients in the last 4 weeks) Week 33: 57 → Week 34: 61 → Week 35: 115 → Week 36: 193

COVID wastewater surveillance (see chart below) shows increasing detection in sewage.




While none of this tells us much about the severity of this year's flu season, it does suggest that it may be upon us sooner than we expect. Of course, what happens in Asia isn't necessarily a harbinger for what we see in North America or Europe, but it is definitely worthy of our attention.

The U.S. CDC should publish their updated Respiratory Virus Activity Levels report later today, but last week's report showed very little flu, and low, but rising COVID activity.

Stay tuned. While things are quiet now, it could be a bumpy fall.

https://afludiary.blogspot.com/2026/09/south-korean-cdc-issues-early-seasonal.html