Severe flu strain ‘Subclade K’ spreading through US

This year's flu is expected to be more severe than usual, and may be more so for those that have not gotten a flu shot, experts say. Data from the US Center for Disease Control show that deaths from the strain as well as hospital visits have been increasing with the strain, known as H3N2, a mutated strain of influenza A.

According to Today, experts have said that the strain of the flu has mutated and may allow for the strain of the illness to escape prior immunity from flu shots. The strain has gained dominance in the Northern hemisphere this year.

New York has seen record flu cases ever seen in one week and surged a number of cases in Japan, Dr. Robert Hopkins Jr, the National Foundation for Infectious Diseases said.

Subclade K has also been seen in Europe and is driving an intense flu season over half the continent. H3N2 is generally more severe across all age groups, but the elderly as well as younger children are more vulnerable. The states so far with the highest flu activity are New York, Colorado, Louisiana, and New Jersey. The CDC has estimated that this flu season has seen 4.6 million cases of illness, 49,000 hospitalizations, and 1,900 deaths.

The 2024-2025 flu season was also considered to be a "high severity" season, but that is generally not common. Hopkins said, "We don’t generally see two severe flu seasons on top of each other ... there’s no rules in this game, so it certainly is possible that we’re going to have another severe season."

He also stressed the importance of getting a flu shot, even though it may not prevent illness, but may reduce its severity. “The goal of vaccines is to reduce the severity of illness, and reduce the disease impact on our population," Hopkin said.

The symptoms caused by the strain of the flu include fever, chills, body aches, headache, extreme fatigue, congestion, and coughing.