Update: Conjunctivitis as a Potential Indicator of H5N1

Wisconsin Department of Health Services

Bureau of Communicable Diseases Information Update

Update: Conjunctivitis as a Potential Indicator of H5N1

Reminder to providers to assess for H5N1 exposure risks when presented with patients with conjunctivitis or acute respiratory infection

This message is being sent to local health officers, Tribal health directors, and the health alert network.

This is an update to the previous bulletin that was sent on October 29, 2024. The below message has been updated to provide additional clarification on testing for influenza A(H5N1) in symptomatic patients.

Key points

  • Highly pathogenic avian influenza (HPAI) A (H5N1) has caused outbreaks in U.S. dairy cattle and poultry; several recent human cases have been detected in U.S. dairy and poultry workers.
  • Many human cases infected after exposure to dairy cattle or poultry have experienced conjunctivitis, either as the only symptom or alongside acute respiratory infection (ARI) symptoms. Many of these cases were positive on the conjunctival swab only, and negative on a nasopharyngeal swab.
  • Clinicians should assess occupational and recreational exposures to animals for patients presenting with conjunctivitis or ARI.
  • Providers should contact the Bureau of Communicable Diseases for consultation and approval for testing at the Wisconsin State Laboratory of Hygiene (WSLH) for:
    • Patients with conjunctivitis or ARI who are suspected to be infected with HPAI A (H5N1), because of exposure to infected or sick dairy cattle, poultry, or any other animal suspected to have HPAI.
    • Patients with conjunctivitis and exposure to dairy cattle or poultry, even without suspected exposure to HPAI A (H5N1).
  • If conjunctivitis is present, a conjunctival swab must be collected alongside a nasopharyngeal swab. Both specimens can be tested at WSLH with approval by the Bureau of Communicable Diseases.
  • Consider local influenza testing, especially by PCR, for patients with ARI and without conjunctivitis, but with exposure to dairy cattle, poultry, or swine. If specimens are positive for influenza A at the local lab, please send to WSLH for further testing and subtyping.

Background

Highly pathogenic avian influenza (HPAI) A (H5N1) is currently circulating among animals in the U.S., with more than three dozen reported human cases to date in 2024. All but one of these cases have been occupationally linked to animal exposures, either on dairy farms or poultry farms. Conjunctivitis has been one of the most common and notable features of these cases, although respiratory and other flu-like symptoms have also been noted.

To date, there have been no known HPAI A(H5N1) dairy cattle outbreaks in Wisconsin; however, the potential for undetected animal infections and animal-to-human transmission cannot be fully ruled out. Studies of retail dairy products have also shown traces of deactivated HPAI A (H5N1) in pasteurized dairy products from states without known dairy cattle outbreaks. While there is no food safety concern with such pasteurized products, the results raise the possibility of infected but undetected dairy herds in some states thought not to be affected by HPAI A (H5N1). For this reason, it is critical that clinicians are vigilant when assessing individuals with exposure risk factors and clinically consistent symptoms, such as conjunctivitis, for HPAI A(H5N1).

Assess occupational or recreational exposure risks for patients with conjunctivitis or respiratory symptoms

Patient occupation should be collected from patients presenting with conjunctivitis and/or ARI. Occupational exposures are particularly important for this outbreak, but asking your patients about work is a general best practice that can be used to help identify any number of occupational exposures or diseases.

Additionally, patients with conjunctivitis or cold and flu symptoms should be asked whether they have had recent contact with dairy cows, raw milk, poultry, or any sick or dead wild birds or animals through occupational or recreational exposures. While dairy and poultry farm workers are thought to have the greatest risk, occupational risk factors have also been identified for veterinary workers, animal health responders, public health responders, dairy laboratory workers, and workers in certain meat and dairy processing roles.

Though the risk to the general public is low, potential recreational exposures such as farm visits should also be considered even if the individual did not have direct contact with dairy cows or poultry.

Please contact your local or Tribal health department or the Bureau of Communicable Diseases at 608-267-9003 for assistance determining which situations may warrant testing for influenza A (H5N1).  

What to do if you suspect a patient has H5N1

Specimens from symptomatic patients suspected of being infected with HPAI A (H5N1), such as people who have exposures to ill or suspected infected animals, should be sent to the WSLH for novel influenza A testing with the prior approval of the Wisconsin Department of Health Services (DHS), Division of Public Health at no charge.

To obtain approval for testing, please contact the Bureau of Communicable Diseases at 608-267-9003.

Clinicians should also consider HPAI A (H5N1) infection in patients with conjunctivitis or ARI, who have exposures to dairy cattle or poultry that are not highly suspected of being infected with HPAI A(H5N1) or for which animal health status is unknown.  If conjunctivitis is present, a conjunctival swab along with a nasopharyngeal swab should be sent to the WSLH after consultation with the Bureau of Communicable Disease.

Clinicians should consider local influenza testing, particularly by PCR, for patients with ARI and without conjunctivitis, but with exposure to dairy cattle, poultry, or other animals that might carry novel influenza A viruses. If specimens are positive for influenza A at the local lab, please send to the WSLH for further testing and subtyping.

Prevention information for individuals with occupational risk factors

Clinicians are encouraged to provide education to occupationally at-risk patients on strategies to prevent HPAI A (H5N1). Prevention resources are available in both English and Spanish on the CDC (Centers for Disease Control and Prevention) and DHS websites.  

Additionally, dairy and poultry workers are a priority population to receive the seasonal flu vaccination this season. While the seasonal flu vaccination does not protect against HPAI A (H5N1), it can reduce the possibility of seasonal flu and HPAI co-infections in occupationally at-risk individuals. Routine seasonal flu vaccination of animal workers is a long-standing recommendation to reduce the potential for viral reassortment resulting from human and animal influenza co-infections.

Contacts

For questions regarding HPAI A (H5N1) testing recommendations, please contact the Bureau of Communicable Disease at dhsdphbcd@dhs.wisconsin.gov.  

For questions about occupational exposures to HPAI A (H5N1), please contact DHS Occupational Health at DHSOccHealth@dhs.wi.gov.

Additional Resources

For health care providers:

For patients and members of the public: