A fast-spreading new flu variant is driving a sharp rise in influenza cases across the United States, with health officials warning that infections are likely to continue climbing amid peak holiday travel and gatherings. The variant, known as subclade K, has already fueled early outbreaks in the United Kingdom, Japan, and Canada and is now accelerating flu activity across the U.S., where the virus typically gains momentum in December. According to the U.S. Centers for Disease Control and Prevention (CDC), more than half of U.S. states are currently experiencing high or very high levels of flu-related illness. As of Dec. 20, the agency estimates at least 7.5 million illnesses, 81,000 hospitalizations, and 3,100 deaths this flu season, including at least eight pediatric deaths. Those figures do not yet reflect the impact of major holiday travel and gatherings. Some states see record-breaking case numbers Several states are reporting unusually high flu activity. New York State recorded 71,000 cases in a single week ending Dec. 20 — its highest weekly total since 2004, according to state health officials. Despite the surge, experts say it is still too early to determine whether this flu season will be as severe as last winter's. What is subclade K and why does it matter? Influenza viruses constantly mutate, producing new variants over time. Subclade K is a mutated form of the H3N2 strain, one of the two subtypes of Type A flu. "H3N2 seasons are generally more severe, especially for older adults," said Andrew Pekosz, a virology expert at Johns Hopkins Bloomberg School of Public Health. While subclade K is not considered a completely new flu virus, its mutations allow it to partially evade immunity from this year's vaccine, Pekosz said. Will the current flu vaccine still help? Health experts emphasize that it is not too late to get vaccinated. Although the current flu shot is not a perfect match for subclade K, early data from the UK suggest it still provides partial protection, particularly against severe illness and hospitalization. The vaccine remains a strong match against other circulating strains, including H1N1 and Type B influenza, which may also spread later in the season. So far, only about 42% of Americans — adults and children combined — have received a flu vaccine this year, according to CDC data. Who is most at risk? Flu poses the greatest danger to: * Adults aged 65 and older * Pregnant women * Young children * People with chronic conditions such as asthma, diabetes, heart disease, or weakened immune systems The CDC recommends annual flu vaccination for everyone aged six months and older. In addition to vaccines, prescription antiviral medications can reduce flu severity, particularly for high-risk patients, but they must typically be started within one to two days of symptom onset. Vaccination options expand Flu vaccines are available as injections for all age groups, as well as the FluMist nasal spray for people aged 2 to 49. For the first time this season, some individuals may be eligible to self-administer FluMist at home, expanding access as flu activity intensifies nationwide. — Agencies
