Last week, the Centers for Disease Control and Prevention (CDC) issued a Health Advisory recommending influenza A testing for all hospitalized patients with suspected influenza, and also recommending expedited subtyping for influenza A-positive specimens.
Providers and clinical laboratories in Washington should:
- IMMEDIATELY notify the Local Health Jurisdiction when any patient is suspected of having highly pathogenic avian influenza (HPAI) A(H5N1).
- Continue to test all hospitalized patients with compatible symptoms for influenza.
- For hospitalized patients with suspected influenza, start empiric antiviral treatment with oseltamivir as soon as possible; additional or combination therapy may be recommended for patients with HPAI A(H5N1).
- Subtype all influenza A-positive specimens from hospitalized patients in the hospital clinical laboratory or send to a commercial laboratory.
- Prioritize subtyping for critically ill patients, especially those in the Intensive Care Unit (ICU).
- IMMEDIATELY notify the Local Health Jurisdiction when influenza A specimens sent for subtyping result as unsubtypeable.
- Forward unsubtypeable influenza A specimens to the Washington State Public Health Laboratory according to specimen submission guidelines.
Current Situation
Seasonal influenza activity is currently high in Washington State, and across the US. In addition to seasonal influenza activity, sporadic human cases of highly pathogenic avian influenza A (HPAI) H5N1 (hereafter “HPAI A(H5N1)”) have been identified across the US, associated with the ongoing H5N1 outbreak in wild birds, poultry, dairy cows and other wild and domestic animals.
Clinicians and laboratorians in Washington are reminded to test for influenza in patients with suspected influenza and, going forward, to now expedite the subtyping of influenza A-positive specimens from hospitalized patients, particularly for patients admitted to ICUs. This approach can help prevent delays in identifying human infections with HPAI A(H5N1) viruses, supporting optimal patient care, timely infection prevention and control, and public health case investigation and contact tracing.
Actions Requested:
Recommendations for Clinicians
- Test all hospitalized patients with compatible symptoms for influenza, ideally within 24 hours of hospital admission.
- If a patient tests positive for influenza via a rapid diagnostic test, providers are encouraged to collect a new specimen that allows for influenza subtyping.
- For any patients that test positive for influenza A: If the initial diagnostic test does not subtype [e.g., identify A(H1) and A(H3)], order influenza subtyping.
- Any hospitalized patients, especially those in an ICU, with suspected seasonal influenza or HPAI A(H5N1) should be started on antiviral treatment with oseltamivir as soon as possible without waiting for the results of influenza testing.
- Consider combination antiviral treatment (e.g., oseltamivir and baloxavir) for hospitalized patients with HPAI A(H5N1) virus infection.
- In Washington, clinicians and facilities are required to IMMEDIATELY report the following to their local health jurisdiction:
- Unsubtypeable influenza A specimens (meaning specimens where the subtype of influenza could not be determined by available tests)
- Suspected or confirmed cases of novel influenza, including HPAI A(H5N1)
- When collecting exposure history from hospitalized patients with suspected or confirmed influenza, ask about potential exposure to:
- Implement appropriate infection control measures when influenza is suspected.
- If HPAI A(H5N1) virus infection is suspected 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).
Recommendations for Clinical Laboratories
- If possible, subtype all influenza A-positive specimens from hospitalized patients in the hospital clinical laboratory.
- If the result is unsubtypeable, immediately notify your local health jurisdiction and ship specimen(s) to Washington PHL as soon as possible and within 24 hours of obtaining the results.
- Follow specimen shipping and handling guidance outlined by the Washington PHL.
- If subtyping is not available in-house, specimens should be sent to a commercial laboratory that offers influenza subtyping.
- If influenza A virus subtyping is NOT available through clinical or commercial laboratories, the Washington PHL may have capacity to offer subtyping for influenza A positive specimens on a limited basis. Specimens may be prioritized at PHL based on the following criteria:
- Influenza A-positive specimens from hospitalized patients with known exposure to wild animals, sick or deceased animals, raw animal products, or suspected or confirmed HPAI A(H5N1) patients
- Influenza A specimens with an unsubtypeable result
- Influenza A specimens that have NOT been subtyped from a patient admitted to an ICU
- All other hospitalized patients with specimens that tested positive for influenza A but have NOT been subtyped.
- If influenza A virus subtyping is NOT available through clinical or commercial laboratories, the Washington PHL may have capacity to offer subtyping for influenza A positive specimens on a limited basis. Specimens may be prioritized at PHL based on the following criteria:
Background
Since 2022, an ongoing global outbreak of highly pathogenic avian influenza (HPAI) A(H5N1) in wild birds, with transmission to poultry and certain mammals, including dairy cattle, has resulted in 67 cases of HPAI A(H5N1) in humans in the United States with 66 of these cases occurring in 2024.
The first human cases of H5N1 were identified in Washington State in October 2024 among people who had close, prolonged contact with infected poultry or their environment. While the human cases identified in Washington have been mild, at least one fatal US case of H5N1 has been identified in a Louisiana patient who was admitted to an ICU.
CDC has routinely recommended influenza testing for hospitalized patients with suspected influenza. In light of the continued circulation of avian influenza A(H5) virus among wild and domestic animals in the United States, CDC and WA DOH now recommend subtyping of all influenza A virus-positive specimens from hospitalized patients on an accelerated basis. This subtyping effort is part of a comprehensive national strategy to identify severe human infections with HPAI A(H5N1) viruses, in addition to characterizing seasonal influenza viruses in a timely fashion.
Rapid influenza A virus subtyping of specimens from hospitalized patients, especially from those in an ICU, can help avoid potential delays in identifying human infections with avian influenza A(H5) viruses. Such delays are more likely while seasonal influenza activity is high, as it is now, due to high patient volumes and general burden on healthcare facilities. Subtyping is especially important in people who have a history of relevant exposure to wild or domestic animals infected or possibly infected with HPAI A(H5N1) viruses.
CDC still considers the risk from HPAI A(H5N1) viruses to the public to be low, but is closely monitoring this dynamic situation. At this time, while seasonal influenza levels are high nationally, nearly all people who are currently hospitalized with influenza A virus infections likely have seasonal influenza.
Resources
- Avian Influenza | Washington State Department of Health
- WA DOH Health Alert: Preumptive Positive Human Cases of Avian Influenza Under Investigation in Washington; Recommendations for Human Health Investigation and Response
- CDC: Clinical Overview of Evaluating and Managing Patients Exposed to Birds Infected with Avian Influenza A Viruses of Public Health Concern
- CDC: H5N1 Bird Flu: Current Situation
- CDC: Health Alert Network (HAN) – 00520 | Accelerated Subtyping of Influenza A in Hospitalized Patients
- CDC: Interim Guidance on the Use of Antiviral Medications for Treatment of Human Infections with Novel Influenza A Viruses Associated with Severe Human Disease
- CDC: Interim Guidance for Infection Control Within Healthcare Settings When Caring for Confirmed Cases, Probable Cases, and Cases Under Investigation for Infection with Novel Influenza A Viruses Associated with Severe Disease
- CDC: Interim Guidance on Specimen Collection and Testing for Patients with Suspected Infection with Novel Influenza A Viruses Associated with Severe Disease or with the Potential to Cause Severe Disease in Humans
Contact
Contact Whatcom County Health and Community Services at 360-778-6100- 360-778-6100 Main Call Line – available M-F 8:30am to 4:30pm.
- Afterhours Answering Service – available after 4:30pm and weekends, call 360-778-6100 and press 2 to be connected to the on-call manager or health officer.
- 360-778-6150 Communicable Disease Report Line – 24 hours a day 7 days a week
- 360-778-6103 Confidential Communicable Disease Fax – 24 hours a day 7 days a week
- 509 Girard Street, Bellingham WA 98225