Seasonal influenza remains a significant cause of morbidity and mortality in the United States. Strategies for prevention, testing, and management continue to evolve and, together, may help to decrease the burden of illness.

The effects of seasonal influenza can produce a heavy economic and societal toll, particularly with respect to increased hospitalizations, morbidity, and mortality, as well as lost productivity. The burden of influenza illness can vary from year to year, depending on the circulating strains that are present, the effectiveness of vaccines and treatment against the circulating strains, and the vulnerabilities of specific populations, such as the pediatric and elderly populations. According to estimates from the Centers for Disease Control and Prevention, the hospitalization burden and resulting health care system strain of fall and winter respiratory diseases for the 2023-2024 season are still expected to be higher than that experienced prior to the COVID-19 pandemic, and severe disease will likely be caused primarily by the influenza virus, the respiratory syncytial virus, and the COVID-19 virus.

According to the Centers for Disease Control and Prevention, diagnostic testing for the influenza virus is not required to prescribe antiviral medications. Instead, a positive diagnosis can be made based on signs and symptoms that are consistent with influenza illness, and empiric therapy can be initiated. However, this is more challenging in the context of COVID-19.

Diagnostic tests that are typically used in outpatient clinics for the identification of influenza include rapid influenza diagnostic tests (RIDTs). RIDTs can detect viral antigen presence within 15 to 20 minutes, but they can also have a high false-negative rate. Rapid molecular assays, which detect genetic material from the influenza virus, are considered more accurate than RIDTs.

In February 2023, the US Food and Drug Administration provided approval under an Emergency Use Authorization for the first over-the-counter at-home test for the simultaneous qualitative detection and differentiation of SARS-CoV-2, influenza A, and influenza B viral nucleic acid for individuals with signs and symptoms of respiratory tract infection, including COVID-19. Labeling information includes guidance on the interpretation of positive and negative test results and notes the importance of working with health care providers to determine how best to proceed based on the test results and other variables (eg, medical history, symptoms, and exposures).

Barring contraindication, antiviral therapy is recommended as soon as possible for any patient with confirmed or suspected influenza who is hospitalized, has severe or complicated illness, or is at high risk for complications from influenza. Health care providers may consider early empiric antiviral therapy for non–high-risk patients with suspected influenza based on clinical judgment. Antiviral therapy is most beneficial when it is initiated as close as possible to the onset of illness. Therapy options that are currently available include oral oseltamivir, inhaled zanamivir, intravenous peramivir, and oral baloxavir marboxil.

Influenza vaccination remains the best way to prevent influenza and its potentially serious related complications. Overall, influenza vaccination has been shown to prevent millions of influenza illnesses and related doctor visits and tens of thousands of hospitalizations every year. It is important to note, however, that the influenza vaccine can vary in its overall and strain-specific effectiveness from year to year. The 2023-2024 influenza vaccinations will include only quadrivalent vaccines—no trivalent vaccines will be available.

Considering the evolving diagnostic and therapeutic landscape, Expert Perspectives in Influenza will include a series of articles exploring clinical considerations in the identification, prevention, and management of influenza, including such topics as the role of seasonal and epidemiological influences, emerging therapeutic options, and changes in testing recommendations and availability.