Japan’s nationwide acute respiratory infection surveillance counted 37.73 influenza cases per sentinel medical institution in week 46, which began 10 November, marking a thirteenth straight weekly gain as pediatric and internal-medicine clinics fill with fever visits. Hana Inoue’s health desk pairs the bulletin with laboratory data showing A/H3 dominance—particularly subclade K—in recent Tokyo specimens, a mix that can stress schools before year-end holidays.
Scale of the uptick
The week 46 bulletin reported 145,526 influenza cases nationally against 3,857 reporting sites, with the broader acute respiratory category also rising week on week. Influenza’s growth rate versus the prior week remained elevated; COVID-19 and RSV reports were far smaller per site, with RSV continuing a multi-week decline in pediatric sentinels.
By prefecture, Miyagi, Saitama, and Fukushima posted the highest per-site influenza counts in the national ranking—useful for travelers checking domestic routes, not just Tokyo commuters.
Pathogen lab picture
Tokyo metropolitan testing through early November found A/H3 subclade K in most influenza-positive specimens, a lineage distinct from last season’s dominant A/H1 wave. That subtype shift can reduce prior-season cross-protection, nudging organizers toward ventilation and absentee policies even when attendance mandates are gone.
Clinical pressure
Weekend and evening clinics already report longer queues for rapid tests and antiviral prescriptions within the 48-hour window. Employers reviewing return-to-office rules should treat week-46 data as early season momentum, not a peak—historically, January can run hotter once schools resume after New Year.
Vaccination coverage for the 2025–2026 trivalent formula remains the primary mitigation lever public health agencies cite; uptake among working-age adults still trails seniors.
What readers can do
Households planning travel across prefectures with high sentinel counts should pack masks and fever reducers, and confirm hotel cancellation policies for illness. Inoue notes that norovirus clusters on cruises and year-end parties run on a parallel track unrelated to influenza but competing for the same clinic bandwidth in port cities.
Bottom line
Week 46 is a national accelerant, not yet Tokyo’s formal epidemic alert threshold, but directionally clear: influenza season is early and climbing. The next two surveillance PDFs will show whether subclade K keeps the curve steep into December.
School and workplace policy
Education boards in high-incidence prefectures are revisiting absentee thresholds as week 46 overlaps with university entrance season travel. Companies with large call-center footprints track absenteeism correlations; some reinstate mask recommendations without mandating them, a compromise HR teams use when formal epidemic alerts have not yet fired in every city.
Antiviral stock
Pharmacy chains report stable oseltamivir supply but uneven zanamivir inhaler availability in rural wards. Inoue advises rural travelers to confirm pharmacy hours because fever clinics refer patients outward when rapid-test swabs run short on Sunday nights.