As flu season hits, new ‘K’ variant has health experts concerned and urging vaccinations

With the holiday season approaching and winter just around the corner, health officials are emphasizing the importance of getting vaccinated against the flu, while also expressing concern about a newly emerging variant.

The A H3N2 influenza virus, which has historically caused hospitalizations and deaths, especially among older adults, is the predominant strain so far this flu season. According to the Oregon Health Authority, 58.2% of positive flu tests analyzed at the Oregon State Public Health Laboratory were identified as H3, while 41.2% were H1N1.

While the H3N2 strain is covered by the 2025-26 flu vaccine, a mutation of this strain, known as subclade K, is becoming increasingly common, causing some worry. Data from the U.S. Centers for Disease Control and Prevention shows that subclade K accounts for 89% of the H3N2 viruses analyzed since late September.

The World Health Organization reported that subclade K has been detected in at least 34 countries over the past six months.

Even with questions about the vaccine's effectiveness against subclade K, health experts still recommend flu shots. They emphasize that vaccinations can lessen the severity of the illness, provide protection against other flu strains, and help to curb the overall spread of the virus.

Dr. Howard Chiou of the OHA's public health division stated, “It’s not too late to get your flu shot, especially before the upcoming holidays. The flu shot is the best way to help make sure you don’t miss out on holiday festivities or get other people sick.”

The CDC advises annual flu vaccinations for everyone 6 months and older. The Oregon Health Authority reports that nearly 1 million Oregon residents had received their flu shots as of early this month. That said, the reality is a bit more complicated. this figure is about 5% lower than the vaccination rate at the same time last year, continuing a recent trend of declining flu vaccination rates, according to the OHA.

To find a vaccination location, individuals can use the VaccineFinder website and enter their ZIP code.

Currently, flu cases remain low across the United States, with high rates reported in only four states: Colorado, Louisiana, New Jersey, and New York. That said, the reality is a bit more complicated. cases are increasing ahead of an expected peak in early spring.

Since the start of flu season on October 1, the OHA has reported 63 hospitalizations related to influenza in Multnomah, Clackamas, and Washington counties.