First Case of HPAI A(H5N1) Virus Infection in US Dairy Farm Worker

In late March 2024, a dairy farm worker in Texas reported symptoms including redness and discomfort in the right eye. Both conjunctival and nasopharyngeal swab specimens from the worker tested positive for influenza A, specifically A(H5) virus, with subsequent confirmation by the CDC for HPAI A(H5N1) virus.¹

Erin Sorrell PhD MSc holds a master’s in virology and is a Senior Scholar at the Center for Health Security at Johns Hopkins. She is a faculty member in the Department of Environmental Health and Engineering at the Bloomberg School of Public Health.

“We need to understand and assess the different types of exposure risks that our agricultural workforce comes into contact with daily, and create better evidence-based approaches to their protection, whether that's through education and advocacy or physical equipment, like personal protective equipment, like goggles, gloves, boots, when those are necessary and when those may not be necessary,” according to Sorrell. “He did not have goggles on so that could have been either transmission where there might have been infected milk on his hands, he rubbed his face and it got into his eyes that way.”

The genomic analysis identified the virus as belonging to clade 2.3.4.4b (genotype B3.13), consistent with strains circulating in Texas dairy cattle and peridomestic wild birds. The virus exhibited a genetic mutation (PB2 E627K) associated with enhanced adaptation to mammalian hosts.

“The stress should be beyond this outbreak is thinking about improved occupational health and safety for agricultural workers, because this scenario could happen again,” according to Sorrell. “We really need to be able to not only respond to the current situation but adapt and prevent future exposure risks.”

The infected worker was isolated, and antiviral treatment with oseltamivir was initiated. Existing candidate vaccine viruses closely match the hemagglutinin of the circulating strain, providing a potential avenue for vaccine development should the need arise.

Supporting Information about Transmission and Prevention from the CDC ²

Transmission and Exposure:

• Human infections mainly occur through close or prolonged exposure to infected birds, their contaminated environments, or infected animals.

Prevention Measures:

• Avoid unprotected contact with sick or dead animals, including birds and other domesticated or wild animals.
• Wear appropriate personal protective equipment (PPE) when in contact with infected animals or their environments.
• Avoid consumption of uncooked or undercooked food products from infected animals.

Monitoring and Management:

• Monitor for respiratory illness symptoms in individuals exposed to infected birds or animals.
• Consider antiviral post-exposure prophylaxis for those with unprotected exposure.

Clinical Management:

• Consider HPAI A(H5N1) virus infection in persons with acute respiratory illness and relevant exposure history.
• Promptly arrange testing and initiate empiric antiviral treatment for suspected cases.

Occupational Safety:

• Individuals working with poultry, livestock, or wildlife should avoid direct contact with sick animals or contaminated materials.
• Wear appropriate PPE to reduce the risk of infection.

Public Health Response:

• State health departments should promptly investigate potential human cases and collaborate with relevant agencies for surveillance and testing.

References

1. Highly Pathogenic Avian Influenza A(H5N1) Virus Infection in a Dairy Farm Worker. The New England Journal of Medicine. Published May 3, 2024. Accessed May 15, 2024. Doi: 10.1056/NEJMc240537

2. CDC. Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations. Last Reviewed May 14, 2024. Accessed May 15, 2024. https://www.cdc.gov/flu/avianflu/hpai/hpai-interim-recommendations.html