H5N1 Highly Pathogenic Avian Influenza Update

(Updated 07/08/2025)

 

Background

 

Since 2022, a very large H5N1 avian influenza outbreak emerged in wild birds worldwide, including in North America. This outbreak continues and has affected many wild birds and poultry farms in Wisconsin and across the U.S.

In spring 2024, H5N1 avian influenza was detected in dairy cows in Texas. Since that first detection, H5N1 avian influenza has been found in over 1,000 cattle herds across 17 states.

Since the beginning of 2024, 70 human cases of H5N1 have been detected in the U.S., including one case in Wisconsin. There has been one fatality in the U.S..

Although CDC’s Risk Assessment for the general population remains LOW, additional precautions are being taken to enhance surveillance for avian influenza across the country.

In Wisconsin, there have been no documented dairy cattle cases of avian influenza. People who have close contact with poultry or dairy cattle infected with H5N1 avian influenza are at increased risk for infection.

 

Highly Suspect Avian Influenza Cases

 

Requesting DPH approval for STAT testing of highly suspect avian influenza cases at the WSLH

 

Clinicians who suspect influenza virus infection in symptomatic patients with known exposure to the following should contact the Wisconsin Division of Public Health (DPH) to request rapid subtype-specific PCR testing at the WSLH –

  • Ill or dying animals or their products
  • Confirmed H5N1 positive flock/herd
  • Person with a probable or confirmed case of H5N1

Weekdays during normal business hours – call DPH at 608-267-9003.

After hours – call DPH at 1-800-943-0003 (option 4) and ask for “the communicable disease epidemiologist on-call”.

NOTE: If the patient has bovine, swine or avian exposure that DOES NOT fit in with the categories listed above, DHS does NOT need to be notified, and the specimen should be sent in for influenza surveillance on the normal WSLH respiratory surveillance requisition form (Laboratory-Based Surveillance Plan 2024-25)

 

Avian Influenza Specimen Collection and Submission to WSLH
  • Collect one nasopharyngeal (NP) swab and place in a tube of viral transport medium (VTM). (Note: For patients with conjunctivitis, additionally, obtain a conjunctival swab and place in a tube of VTM.)
    • Use swabs with a Dacron or polyester tip with an aluminum or plastic shaft.
  • For patients with lower respiratory illness, collect a lower respiratory tract specimen (e.g., BAL).
  • Request an “Enhanced Surveillance” requisition form upon DPH approval by contacting WSLH Customer Service at 800-862-1013. Complete and submit a form for each submitted specimen.
    • Please check “Avian Influenza Suspect” under reason for submission.
  • Arrange transport so that specimens arrive at the WSLH within 24 hours of collection. Avian influenza suspects can be shipped Category B.
    • Specimens can be transported to the WSLH by a carrier of your choice, or at NO COST when using Purple Mountain Solutions (PH: 800-990-9668).
  • Please contact the WSLH Customer Service Department at 800-862-1013 if you have any questions regarding laboratory testing.
Suspect Avian Influenza Testing at the WSLH
  • Testing is usually completed within 24 hours of specimen receipt at the WSLH.
  • There is no charge for avian influenza testing at the WSLH.
  • Suspect avian influenza specimens that are submitted to the WSLH will first be tested with the CDC influenza A/influenza B/SARS-CoV-2 multiplex PCR assay.
    • You will always receive a result for influenza A/influenza B/SARS-CoV-2 multiplex PCR.
  • If a specimen is positive for influenza A, it will also be tested with a seasonal influenza A subtyping PCR and the influenza A – H5 specific subtyping PCR.
    • You will receive a result for the seasonal influenza A seasonal subtyping PCR and the Influenza A/H5N1 subtyping PCR.
Additional Information

Wisconsin Department of Health Services, Avian Influenza A Virus
CDC’s Flu Surveillance Systems Can Detect Avian Influenza A (H5N1) Virus Infections
CDC Avian Influenza guidance documents and information

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