A new mutation of the influenza A(H3N2) strain, termed subclade K, is contributing to a surge in flu cases and hospitalizations across Texas and the broader United States as this year’s flu season progresses. This variant exhibits notable characteristics that reduce the effectiveness of the current flu vaccine, as there are significant differences between subclade K and the strain used to develop the vaccine. The mutations have altered the virus’s structure enough that many individuals who have been vaccinated may find their immune response ineffective or, in some cases, fail to recognize the virus completely. This phenomenon, known as antigenic drift, is highlighted by the Centers for Disease Control and Prevention (CDC).
According to Texas Health and Human Services, the state has seen a marked increase in flu-related health visits, surpassing 5,000 weekly visits for three consecutive weeks, with reports ending Nov. 22, Nov. 29, and Dec. 6. This figure represents more than double the number of cases reported at the same period last year, with East Texas alone accounting for approximately 250 visits per week.
Hospitalization rates have also escalated, particularly among individuals aged 65 and older. As of the week ending Dec. 6, the hospitalization rate for this age group rose to 7.4 per 100,000 residents, a significant increase from just 2.2 per 100,000 a month prior.
Despite the emergence of subclade K, the CDC continues to recommend getting vaccinated. The vaccine still holds the potential to protect against severe illness, hospitalization, and death from influenza, alongside other circulating strains included in the vaccine formulation.
As the flu season is still evolving, with increased transmission expected during the upcoming holiday travel period and into late winter, now is an opportune moment for individuals to receive their vaccinations to mitigate the risk and impact of the virus.