CDC

Health Advisory: CDC calls for accelerated testing for influenza A in hospitals

January 16, 2025

In light of the ongoing avian influenza A(H5) virus animal outbreak in the U.S., CDC now recommends subtyping of all influenza A virus-positive specimens from hospitalized patients on an accelerated basis. This accelerated subtyping is part of a comprehensive strategy to identify severe human infections with avian influenza A(H5) viruses, in addition to characterizing seasonal influenza viruses in a timely fashion.

Recommendations for testing of hospitalized patients

In addition to jurisdiction-specific instructions for sending specimens for subtyping, CDC now recommends that all influenza A positive respiratory specimens from hospitalized patients, especially from those in an ICU, be subtyped for seasonal influenza A viruses [A(H1) and A(H3)] as soon as possible following admission—ideally within 24 hours—to support optimal patient care and proper infection prevention and control measures and to facilitate rapid public health investigation and action.

Recommendations for clinicians

• When collecting a thorough exposure history from a patient with suspected or confirmed influenza who is hospitalized, ask about potential exposure to wild and domestic animals, including pets (e.g., cats), and animal products (e.g., poultry, dairy cows, raw cow milk and raw cow milk products, raw meat-based pet food), or recent close contact with a symptomatic person with a probable or confirmed case of A(H5).
• Implement appropriate infection control measures when influenza is suspected.
• If avian influenza A(H5) virus infection is suspected, probable, or confirmed in a hospitalized patient, place the patient in an airborne infection isolation room with negative pressure with implementation by caregivers of standard, contact, and airborne precautions with eye protection (goggles or face shield).
• Test for seasonal influenza A in hospitalized patients with suspected seasonal influenza or novel influenza A virus infection such as avian influenza A virus infection, using whatever diagnostic test is most readily available for initial diagnosis.
• If the initial diagnostic test does not subtype [e.g., identify A(H1) and A(H3)], order an influenza A subtyping diagnostic test within 24 hours of hospital admission for patients who tested positive for influenza A.
• Subtyping should be performed with assays available to the testing laboratory, as follows:
  Subtyping tests should be performed in the hospital clinical laboratory, if available.Alternatively, specimens should be sent to a commercial clinical laboratory.If influenza A virus subtyping is not available through one of these routes, arrangements can made for influenza A virus-positive specimens to be subtyped at a public health laboratory.
• Any hospitalized patients, especially those in an ICU, with suspected seasonal influenza or avian influenza A(H5) should be started on antiviral treatment with oseltamivir as soon as possible without waiting for the results of influenza testing.
• Consider combination antiviral treatment for hospitalized patients with avian influenza A(H5) virus infection.
• Notify the health department promptly if avian influenza A(H5N1) virus infection is suspected, probable, or confirmed in a hospitalized patient.
• Questions about appropriate clinical management or testing of hospitalized patients with novel influenza A virus infection [e.g., A(H5)], including about combination antiviral treatment dosing or testing for antiviral resistance, can be directed to the CDC Influenza Division for consultation with a medical officer via the CDC Emergency Operations Center at 770-488-7100.

Source:

(2025, January 16). CDC. Accelerated Subtyping of Influenza A in Hospitalized Patients. https://www.cdc.gov/han/2025/han00520.html