Health authorities across the US and Canada are reporting a sharp rise in influenza cases this season, driven largely by the spread of the H3N2 strain of influenza A, (known as subclade K). The variant is known for its high transmissibility and association with more severe flu seasons.
What exactly is the H3N2 flu variant?
H3N2 is a subtype of influenza A, one of the main categories of seasonal flu viruses that circulate globally each year. Influenza A viruses are classified based on two proteins on their surface, hemagglutinin (H) and neuraminidase (N). The H3N2 subtype has a long history of causing widespread outbreaks and has, in past seasons, been linked to higher rates of hospitalisation, particularly among older adults, young children and people with underlying health conditions.
What are its symptoms?
Subclade K causes more intense symptoms than typical flu strains, including high fever, chills, severe headaches, extreme fatigue, persistent cough, sore throat, and runny nose.
Among 216 influenza A(H3N2) viruses collected by the CDC since September 28, 89.8% belonged to this subclade, confirming its dominance. Experts described it as a “perfect storm” due to its aggressiveness, combined with declining vaccination rates worldwide, according to Fox News.
What about cases in Canada?
Health agencies in Canada have reported growing numbers of laboratory-confirmed influenza cases, with H3N2 accounting for a significant share. Some provinces have seen early spikes compared to previous years, adding strain to healthcare facilities already managing seasonal pressures.
Earlier this month, Canada saw 11,646 new cases of flu being detected, which means 27.7 per cent of all the tests conducted in the country came out positive.
This was an increase of 71 per cent compared with the week before, which saw 6,799 new cases and a positivity rate of 20.2 per cent, Global News reported.
Should you get vaccinated?
In an interview with Fox News, Dr Neil Maniar, professor of public health practice at Boston’s Northeastern University, said it’s uncertain whether this year’s flu vaccine directly addresses this specific mutation.
“The vaccine is very important to get, but because it’s not perfectly aligned with this variant, I think that’s also contributing to some degree to the severity of cases we’re seeing,” he said.
“Even healthy individuals can become seriously ill from the flu, so a vaccine is beneficial for almost everyone,” Maniar noted.