Overview
The CDC continues to monitor and respond to the ongoing multistate outbreak of avian influenza A(H5N1), or H5N1 bird flu, affecting dairy cows, poultry, and other animals in the U.S. In collaboration with USDA, FDA, ASPR, state public health and animal health officials, and other partners, CDC is applying a One Health approach to address the outbreak.
Public Health Risk Assessment
The risk to the general public remains low, with no confirmed human-to-human transmission of H5N1. However, individuals with direct exposure to infected dairy cows or poultry are at higher risk of infection.
Human Cases and Dairy Industry Impact
Since April 2024, CDC has confirmed 70 human cases of H5N1 in the U.S., with most infections linked to exposure to infected dairy cows or poultry. In 2025, three human cases have been identified:
- Nevada (Dairy Worker) – Developed conjunctivitis after exposure to infected dairy cows. Recovered without hospitalization.
- Ohio (Poultry Worker) – Experienced severe respiratory symptoms and was hospitalized. Confirmed positive through lower respiratory testing.
- Wyoming (Backyard Flock Owner) – Hospitalized with respiratory symptoms. Recovered and discharged.
Genetic Analysis of the Virus
CDC’s genetic sequencing of the virus from the Nevada and Wyoming cases confirmed mutations associated with increased replication in mammals. These mutations have been previously observed but do not indicate increased transmissibility among humans. No changes were found that would impact the effectiveness of current antiviral treatments or H5 vaccine candidates.
Preventive Measures for Dairy Workers
Given the potential for serious illness, dairy farm workers should follow CDC guidelines to minimize exposure risk. Recommended measures include:
- Wearing personal protective equipment (PPE) when handling potentially infected animals.
- Practicing proper hygiene, including handwashing and avoiding touching the face.
- Reporting any flu-like symptoms to healthcare providers promptly.
Conclusion
While the outbreak remains a significant concern for the dairy industry, the overall risk to the public is low. Continued surveillance, preventive measures, and coordination among federal and state agencies remain critical in managing the impact of H5N1 on both human and animal health.
