December 17, 2025

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Influenza activity is starting to increase across West Virginia. Flu activity is expected to rise in the coming weeks due
to increased travel, gatherings and indoor time that bring people in closer contact. Most flu viruses collected and
analyzed during the 2025-26 respiratory season, have been subclade K, a variant of flu strain H3N2. This new
subclade was first identified by the Centers for Disease Control and Prevention (CDC) in August 2025. Seasons
during which influenza A(H3) cause the majority of influenza infections are typically characterized by more severe
illnesses, particularly among older adults, resulting in more people seeking care.

When circulating influenza viruses have genetically drifted away from the viruses used in the annual vaccine,
individual and population immunity may be lower, which could reduce the vaccine’s effectiveness. The actual impact
of this “antigenic drift” on protection is difficult to predict, but it is important to note that even in past seasons with
drifted viruses, the vaccine has still provided substantial protection.

Recommendations for Clinicians and Public Health Practitioners
• The West Virginia Bureau for Public Health recommends that all eligible persons aged 6 months and older who
have not yet received an influenza vaccination this season be offered one.
• Healthcare providers should promptly initiate treatment with influenza antiviral medications for patients with
confirmed or suspected influenza who are hospitalized, have severe/complicated/progressive disease, or are at
high risk for complications.
• Antiviral drugs are most effective when started within two days of symptom onset but may still offer some
benefit if started later. Treatment decisions should not be delayed while awaiting laboratory confirmation.
• For hospitalized patients or those with complications (like pneumonia) or progressive disease, oral or enterically
administered oseltamivir (Tamiflu) is the recommended antiviral treatment.
• For outpatients with uncomplicated influenza, oral oseltamivir (Tamiflu), oral baloxavir marboxil (Xofluza),
inhaled zanamivir (Relenza), and intravenous peramivir (Rapivab) may be used, subject to approved age groups
and contraindications.

 

WV HAN 232 Circulation of Drifted Influenza A(H3N2) Virus 12.17.25