Persons working closely with animals infected with the Highly Pathogenic Avian Influenza (HPAI) A(H5N1) virus, such as dairy cows, poultry, and other animals, are at an elevated risk of contracting the virus.

In late 2024, the California Department of Public Health reported the first human case of HPAI A(H5N1) in California by monitoring farm workers with infected cows.

From September 30 to December 24, 2024, 38 individuals in California tested positive for HPAI A(H5N1). Among these, 37 were dairy farm workers exposed to sick cows in their workplace, and one was a child under 18 with an unknown exposure source. This was the first pediatric HPAI A(H5N1) case reported in the United States. All patients experienced mild illness.

Identifying these cases highlights the continued risk of transmitting HPAI A(H5N1) to individuals working with infected animals.

Who is at increased risk at work?

Individuals with occupational exposure to HPAI A(H5N1) viruses, particularly those in close contact with infected animals like dairy cows, poultry, or other animals, face an increased risk of infection.

During the monitoring period from August 30 to December 24, 2024, 5,126 workers at affected farms were monitored, and 170 individuals from 19 local health jurisdictions were tested for influenza A(H5) through targeted surveillance.

Among the 171 persons who received testing, 36 cases and one probable case of HPAI A(H5N1) were identified among adult dairy farm workers, and one confirmed case was found in a child with no known exposure to dairy cows or poultry.

What precautions should be taken?

The CDC emphasizes that public health agencies should investigate cases of influenza-like illness or conjunctivitis in workers with occupational exposure to animals infected with the HPAI A(H5N1) virus.

Recommended strategies include:

PPE use guidance, training, and distribution.
Collaboration with farm managers on worker monitoring.
Coordination with local health departments for worker testing.
Specimen collection and laboratory testing to differentiate influenza A(H5) from seasonal influenza viruses.
Distribution of oseltamivir treatment to HPAI A(H5N1) patients and oseltamivir prophylaxis to close contacts.

Collaboration among various agencies is crucial for a coordinated response and early detection of influenza A(H5) virus changes that could lead to human-to-human transmission.

Will H5N1 expand into a major pandemic?

As of the date of the reference document, no human-to-human transmission of HPAI A(H5N1) virus has been identified in the United States.

However, the CDC emphasizes the importance of ongoing monitoring for genetic changes in the virus to assess the likelihood of antiviral resistance or human-to-human transmission of HPAI A(H5N1) viruses.

Human Cases of Highly Pathogenic Avian Influenza A(H5N1) — California, September–December 2024

Recommended Citation: Gelman, Jon., Bird Flu Transmission: Occupational Hazards (03/14/2025) https://workers-compensation.blogspot.com/2025/03/bird-flu-transmission-occupational.html

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*Jon L. Gelman of Wayne, NJ, is the author of NJ Workers’ Compensation Law (West-Thomson-Reuters) and co-author of the national treatise Modern Workers’ Compensation Law (West-Thomson-Reuters). For over five decades, the Law Offices of Jon Gelman 1.973.696.7900
jon@gelmans.com has represented injured workers and their families who have suffered occupational illnesses and diseases.