Notes from the Field : Health Monitoring, Testing, and Case Identification Among Persons Exposed to Influenza A(H5N1) — Michigan, 2024

Joseph Coyle, MPH1; Natasha Bagdasarian, MD1; Seth Eckel, MPH1; Jeremy Kuo, MPH1; Mary Grace Stobierski, DVM1; James Barber, MPH1; Meghan Weinberg, PhD1; Fatema Mamou, MPH1; Sarah Lyon-Callo, PhD1; Michigan Local Health Departments; Bureau of Laboratories; Bureau of Infectious Disease Prevention Investigation Team (

Summary

What is already known about this topic?

Highly pathogenic avian influenza (HPAI) A(H5N1) virus has been detected in wild birds and mammals, poultry, and commercial dairy facilities in the United States. A human case in a Texas dairy worker was reported in April 2024.

What is added by this report?

As of May 23, 2024, Michigan had the largest number of affected dairy and poultry facilities linked to the HPAI A(H5N1) outbreak. Active symptom monitoring and testing of exposed workers led to detection of the second and third known dairy-associated HPAI A(H5N1) cases in 2024.

What are the implications for public health practice?

The current risk to the public from HPAI A(H5N1) viruses is low; however, continued symptom monitoring and testing are critical to characterizing genetic or epidemiological changes that might alter the risk assessment.

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On March 25, 2024, a Texas dairy farm detected highly pathogenic avian influenza (HPAI) A(H5N1) virus in cows. The outbreak widely spread after interstate cow movement. During March 25–June 17, animals at a total of 102 dairy farms in 12 states, 24 commercial poultry flocks in five states, and multiple backyard flocks tested positive for HPAI A(H5N1) (1,2). This report describes response activities in Michigan, which led to detection of the second and third human cases related to the 2024 HPAI A(H5N1) outbreak. The activity was reviewed by the Michigan Department of Health and Human Services, deemed not research, and was conducted consistent with applicable federal law, state, and departmental policy.*

Investigation and Outcomes

Infected cows from Texas resulted in introduction of HPAI A(H5N1) virus in a Michigan dairy, detected on March 29. As of May 29, a total of 23 Michigan dairies in 10 counties are known to be affected (1). Michigan’s first affected commercial poultry facility was confirmed on April 2; currently, seven affected poultry facilities in four counties have been identified (2). HPAI A(H5N1) virus has also been detected in a backyard flock, pigeons, foxes, cats, opossums, and a racoon in Michigan. Whole genome sequencing results suggest that, since March 2024, all sequenced isolates have ancestral Texas origins (3).

Monitoring of Dairy Workers

Among the 23 affected dairies, 306 persons exposed to affected cows were identified. Lists of exposed persons were obtained by public health officials from 20 (87%) affected dairies. Workers at 12 (60%) of those dairies were enrolled in text-based daily symptom monitoring,† and workers at eight (40%) farms were monitored through a farm point of contact. Because it could be unclear when workers’ exposures to cows ended, some workers were monitored for >50 days.

Twenty (6.5%) exposed workers reported symptoms and were tested for influenza A(H5) virus infection. Among persons who received real-time reverse transcription–polymerase chain reaction testing,§ one received a positive test result from a conjunctival swab, similar to the case of HPAI A(H5N1) reported from a dairy worker in Texas (4). Before the onset of mild unilateral conjunctivitis, the patient reported direct ocular exposure to raw, unpasteurized milk from an affected cow. A second worker from a different dairy farm experienced respiratory symptoms after close contact with sick cows and received a positive A(H5) virus test result from a nasopharyngeal swab. In both instances, public health officials rapidly collected patient specimens, which tested positive for HPAI A(H5N1). Neither worker was severely ill, neither required hospitalization, and no household or work contacts reported being ill. Both workers wore some personal protective equipment (PPE), but neither wore a mask or respirator.

Monitoring of Poultry Workers

Among seven affected commercial poultry facilities, 857 persons exposed to affected birds were identified. Lists of exposed persons were obtained from all facilities. Workers from four facilities were directly enrolled in text-based daily symptom monitoring, and workers from three facilities were monitored through a farm point of contact who reported results to public health officials. Eighteen (2.1%) symptomatic persons were identified and tested; all test results were negative for influenza A(H5).

Monitoring of Other Exposed Persons

Federal and state employees who responded to affected farms were also observed for symptoms, as were persons with exposure to HPAI A(H5N1) virus–infected animals (domestic or wild) or humans. Overall, 125 such persons were monitored, and 15 (12%) reported symptoms, 14 of whom received negative influenza A(H5) test results.

Preliminary Conclusions and Actions

Among 1,288 Michigan residents who were monitored for signs and symptoms after potential HPAI A(H5N1) virus exposure, 53 (4.1%) reported signs and symptoms, 52 of whom received testing for influenza A(H5). Two dairy workers received positive test results (3.8% of all persons tested, Although the risk for HPAI A(H5N1) virus to the public remains low, novel influenza A viruses such as A(H5N1) have pandemic potential. Therefore, it is critical to notify persons with exposure to infected animals, provide education and access to PPE,¶ monitor signs and symptoms, test specimens collected from any exposed person with signs and symptoms, and make antivirals available to symptomatic persons as soon as possible.**

Although the percentage of workers who regularly used PPE is not known, the human cases associated with dairy farms in Texas and Michigan demonstrate the potential value of PPE, including eye and respiratory protection, especially on affected farms (4,5). The cases identified to date have resulted in mild illness, which might not have been detected without the collaboration of state officials and the engagement of farms and workers. Streamlined, nonintrusive approaches to monitoring, such as the text-message monitoring used in Michigan, might encourage participation and subsequent testing. A One Health†† approach including collaboration with agriculture departments, farms, and workers is crucial to successful public health response.

Acknowledgments

Michigan dairy and poultry producers and farm workers; Michigan Department of Agriculture and Rural Development; People.Health.

Michigan Local Health Departments

Jennifer Johnson, Mid-Michigan District Health Department; Dena Kent, Mid-Michigan District Health Department; Lisa Mikesell, Mid-Michigan District Health Department; Jennifer Morse, Mid-Michigan District Health Department; Becky Stoddard, Mid-Michigan District Health Department; Aimee Feehan, Ionia Health Department; Chris May, Ionia Health Department; Yolanda Rivera, Ionia Health Department; Chad Shaw, Ionia Health Department; Tamara Drake, Ottawa County Health Department; Deral Glashower, Ottawa County Health Department; Adeline Hambley, Ottawa County Health Department; Gwen Unzicker, Ottawa County Health Department; Rikki Fedewa, Central Michigan District Health Department; Susan Leeson, Central Michigan District Health Department; Clare Jansen, District Health Department #10; Kali Nichols, Barry-Eaton Health Department; Maddie Vervaeke, Barry-Eaton Health Department; Lisa Letts, Allegan Health Department; Erin Radke, Allegan Health Department; Elizabeth Baty, Ingham County Health Department; Darcie Cunningham, Ingham County Health Department; Kira Hecksel, Ingham County Health Department; Mary Huffman, Ingham County Health Department; Wai Yi Leung, Ingham County Health Department; Kassi Nelson, Ingham County Health Department; Sumeer Qurashi, Ingham County Health Department; Adenike Shoyinka, Ingham County Health Department; William Nettleton, Calhoun County Health Department; Eric Pessell, Calhoun County Health Department.

Bureau of Laboratories

Katie Margulieux, Michigan Department of Health and Human Services; Diana Riner, Michigan Department of Health and Human Services; Marty Soehnlen, Michigan Department of Health and Human Services; Jalen Stricklen, Michigan Department of Health and Human Services; Jason Wholehan, Michigan Department of Health and Human Services

Bureau of Infectious Disease Prevention Investigation Team

Smeralda Bushi, Michigan Department of Health and Human Services; Derick Chia, Michigan Department of Health and Human Services; Ebonē Colbert, Michigan Department of Health and Human Services; Jim Collins, Michigan Department of Health and Human Services; Justin Henderson, Michigan Department of Health and Human Services; Tiffany Henderson, Michigan Department of Health and Human Services; Shannon Johnson, Michigan Department of Health and Human Services; Sue Kim, Michigan Department of Health and Human Services; Mat Myers, Michigan Department of Health and Human Services; Sarah Pruett, Bureau of Infectious Disease Prevention Investigation Team; Briana Putrus, Michigan Department of Health and Human Services; Bethany Reimink, Michigan Department of Health and Human Services

Corresponding author: Joseph Coyle, CoyleJ@michigan.gov.

1Michigan Department of Health and Human Services.

All authors have completed and submitted the International Committee of Medical Journal Editors form for disclosure of potential conflicts of interest. Natasha Bagdasarian reports travel or meeting support from the Council of State and Territorial Epidemiologists (CSTE), the Association of State and Territorial Health Officials (ASTHO), and Bloomberg; participation on data safety monitoring boards or advisory boards for ASTHO (including the Advisory Council for the Elimination of Tuberculosis and the Infectious Disease Policy Committee), the Center for Emerging and Infectious Diseases, the Center for Emerging and Infectious Diseases Advisory Board at Wayne State University, the Child Lead Exposure Elimination Commission (chair), the Clinical Competency Committee, the Council for Outbreak Response: Healthcare-Associated Infections and Antimicrobial-resistant Pathogens Committee (co-chair), iMPROve Health Board, the Metropolitan Affairs Coalition Healthcare Task Force, the Michigan Department of Health and Human Services (MDHHS) Institutional Review Board, the Michigan Health and Hospital Association Public Health Taskforce, MDHHS Michigan State Health Improvement Plan Steering Committee, the National Kidney Foundation of Michigan Morris Hood III Advisory Committee, the Physicians Health Plan Advisory Board, Preventative Medicine Residency Program Evaluation Committee, the Public Health Advisory Council (chair), the School Safety Commission, the Society for Healthcare Epidemiology of America External Affairs Committee, and the Technical Advisory Group, National Academy of State Health Policy. Fatema Mamou reports travel support from CSTE. Sarah Lyon-Callo reports travel support from CSTE and ASTHO to attend meetings and service as president of CSTE’s executive board and as the MDHHS’s representative on the Michigan Public Health Institute’s Board of Directors. No other potential conflicts of interest were disclosed.

• 45 CFR part. 46; 5 U.S.C. 301; 42 U.S.C. 289(a); 42 U.S.C. 300v-1(b).

† https://people.health/

§ https://www.cdc.gov/bird-flu/php/severe-potential/?CDC_AAref_Val=https://www.cdc.gov/flu/avianflu/severe-potential.htm

¶ https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html

** Antiviral treatment is recommended with oseltamivir as soon as possible for outpatients and hospitalized patients who have suspected, probable, or confirmed cases of human infection with novel influenza A viruses associated with severe human disease. https://www.cdc.gov/bird-flu/hcp/novel-av-treatment-guidance/?CDC_AAref_Val=https://www.cdc.gov/flu/avianflu/novel-av-treatment-guidance.htm

†† One Health is an approach that recognizes the interconnectedness of human, animal, and environmental health. https://www.cdc.gov/one-health/about/index.html

References

• Animal and Plant Health Inspection Service, US Department of Agriculture. Detections of highly pathogenic avian influenza (HPAI) in livestock. Riverdale, MD: US Department of Agriculture, Animal and Plant Health Inspection Service; 2024. Accessed 23 May 2024. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock
• Animal and Plant Health Inspection Service, US Department of Agriculture. Confirmations of highly pathogenic avian influenza in commercial and backyard flocks. Riverdale, MD: US Department of Agriculture, Animal and Plant Health Inspection Service; 2024. Accessed 23 May 2024. https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/commercial-backyard-flocks
• Nguyen TQ, Hutter C, Markin A, et al. Emergence and interstate spread of highly pathogenic avian influenza A(H5N1) in dairy cattle. bioRxiv ; Preprint posted online May 1, 2024] [https://doi.org/10.1101/2024.05.01.591751
• Garg S, Reed C, Davis CT, et al. Outbreak of highly pathogenic avian influenza A(H5N1) viruses in U.S. dairy cattle and detection of two human cases—United States, 2024. MMWR Morb Mortal Wkly Rep 2024;73:501–5. https://doi.org/10.15585/mmwr.mm7321e1 PMID:38814843
• Uyeki TM, Milton S, Abdul Hamid C, et al. Highly pathogenic avian influenza A(H5N1) virus infection in a dairy farm worker. N Engl J Med 2024;390:2028–9. https://doi.org/10.1056/NEJMc2405371 PMID:38700506

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