According to the NIH, the influenza A(H3N2) subclade K has emerged globally during the 2025–26 season. A sharp rise in H3N2 cases has been reported in multiple regions since August 2025.

The advisory said South Asia recorded a significant increase in influenza cases between May and November 2025, with H3N2 accounting for 66 per cent of reported infections. Australia and New Zealand have also reported notable H3N2 activity.

In Pakistan, the NIH observed an increase in influenza-like illness (ILI) and severe acute respiratory infection (SARI) cases. Between epidemiological weeks 44 and 49, a total of 340,856 suspected cases were reported. Of the samples tested, 12 per cent were found positive for H3N2.

The institute warned that older adults, pregnant women, children and people with chronic illnesses are at higher risk of severe illness from the virus.

The NIH described influenza vaccination as the most effective preventive measure. It also advised regular handwashing, observing cough and sneeze etiquette, and avoiding unnecessary crowding to reduce transmission.