The Resurgence of Influenza in the Northern Hemisphere: A Closer Look

The recent spread of influenza, particularly in the United States and the United Kingdom, has garnered attention, with some media outlets using the term "super flu." However, it's crucial to understand that this term is not an official medical designation.

A New Variant Emerges

The actual name for the strain causing concern is subclade K, a new variant of influenza A H3N2. This variant has multiple mutations in a protein on the surface of the virus called hemagglutinin, making it antigenically different from the variants used in existing vaccines. This antigenic shift allows the virus to partially evade immunity acquired through previous infection or vaccines, making people more susceptible to infection.

Early Onset and Global Impact

One concerning aspect of the current epidemic is its early onset. While the usual peak in Japan occurs between late December and February, in 2025, the epidemic began in earnest at the end of September. This early onset may be due to a decline in population immunity due to countermeasures against new coronavirus infection (Covid-19) and a decline in physical strength due to record-breaking heat waves.

Given the early onset and the severity of the flu season in Australia, it would not be surprising to see a similar trend in the Northern Hemisphere, including North East India.

Vaccine Efficacy and Prevention Measures

There has been much interest in vaccine efficacy in the face of this virulent strain. Although the vaccine for the 2025-26 season is based on a different lineage from subclade K, early data from the UK suggests that it remains effective in preventing severe illness. Basic prevention measures, such as vaccination, handwashing, mask-wearing, ventilation, and rest, remain essential.

Responding with Scientific Understanding

Despite the term "super" implying increased danger, it's essential to respond calmly based on scientific understanding rather than fear. The risk of developing severe symptoms can be significantly reduced by combining vaccination with basic infection control measures. By making responsible choices based on accurate information, we can protect the health of society as a whole.

This article was originally published in WIRED Japan and has been translated from Japanese.