type: timeline_event
On October 20, 2024, the Washington State Department of Health and Benton-Franklin Health District reported the first presumptive positive cases of avian influenza A(H5) virus in agricultural workers at a commercial egg farm in Franklin County, Washington. CDC testing ultimately confirmed HPAI A(H5) virus in 8 poultry farm workers who were exposed to H5N1 virus-infected poultry during depopulation efforts to control an outbreak among poultry.
The infections occurred at a farm that had experienced an avian influenza outbreak in chickens, where approximately 800,000 birds were euthanized after test results by the Washington State Department of Agriculture on October 15 showed they were infected with avian influenza. All 8 cases occurred in adults exposed to infected poultry during these mass culling operations, representing the largest cluster of human H5N1 infections at a single U.S. workplace to date.
The infected workers experienced mild symptoms and were provided with antiviral medication. However, the incident highlighted significant gaps in worker protection protocols during emergency disease response operations. The mass infection of workers during depopulation efforts demonstrated that existing safety measures were inadequate to prevent human exposure during high-risk agricultural operations.
Scientific analysis of viral samples from the Washington cases showed they were infected with the D1.1 genotype, which is different from the B3.13 genotype that had been fueling the outbreak on dairy farms. The available gene sequences from the Washington human cases lacked changes associated with reduced antiviral susceptibility or mammalian adaptation, and the virus retained preferential binding to avian-like receptors rather than mammalian receptors.
This outbreak made Washington the sixth state to identify human H5N1 infections and represented a critical failure in occupational safety protocols. The simultaneous infection of eight workers during a single depopulation operation raised serious questions about the adequacy of personal protective equipment, worker training, and safety oversight during emergency agricultural disease response. The incident underscored how industrial-scale poultry operations create concentrated exposure risks for workers, particularly during crisis response operations involving the mass culling of hundreds of thousands of infected birds.