Flu Activity Resurges in the US as Infections Rise Among Children

Flu activity in the United States has seen a noticeable uptick, primarily driven by a resurgence of infections from the influenza B virus. This increase follows a season dominated by the new subclade K strain of influenza A, which has been the predominant strain thus far.

According to data released by the US Centers for Disease Control and Prevention (CDC) on January 24, 2024, cases of influenza B have risen slightly, marking a shift in the flu landscape. Dr. Caitlin Rivers, an epidemiologist who tracks infectious disease trends, indicated that this rise is particularly evident among school-age children aged 5 to 17. “Children and kids are always the first to register new trends,” Rivers stated, suggesting that while the current spike is concentrated in this demographic, adults may soon experience similar increases.

This pattern mirrors last year’s flu season, which also saw a second peak in late February after an initial decline. The recent winter storm affecting much of the United States could also be influencing these trends, according to Rivers.

The CDC’s recent report highlights that while influenza B strains have increased by less than one percentage point from the previous week, influenza A activity remains stable. The emergence of a spring wave of influenza B has not yet been confirmed, but health officials are closely monitoring the situation.

Influenza B belongs to a different family of viruses than influenza A. This distinction means that individuals may contract the flu multiple times in one season if infected with different strains. The current flu vaccine offers protection against two A strains and one B strain, potentially mitigating severe illness and hospitalization risks.

Both influenza A and B typically present similar symptoms, including high fever, sore throat, cough, body aches, and fatigue. Antiviral treatments are available for both types of flu, further aiding in management during the season.

Despite the growing concern around influenza B, the CDC reports that overall flu activity remains robust, primarily driven by the subclade K strain from the H3N2 lineage. Historically, years dominated by H3N2 strains tend to be more severe in terms of illness. As of the week ending January 24, 87% of lab-confirmed flu cases reported to the CDC were attributed to A strains, with approximately 13% from B strains.

The CDC’s national map indicates that 29 states are experiencing high or very high flu activity, while an additional ten states report moderate levels. Tragically, the flu has resulted in eight more pediatric deaths in the past week, raising the total number of flu-related deaths among children this season to 52.

In the broader context of respiratory illnesses, influenza continues to be the leading infection, although cases of Covid-19 and respiratory syncytial virus (RSV) are also on the rise. Health officials urge vigilance as the flu season progresses, especially with the potential for further increases in infection rates.