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The Centers for Disease Control and Prevention (CDC) has confirmed four human cases of highly pathogenic avian influenza (HPAI) A(H5), commonly known as “H5 bird flu,” in Colorado. These cases involve individuals working at a poultry facility experiencing an outbreak of the virus. The CDC is also tracking a fifth presumptive-positive case awaiting confirmation at its laboratories. This development underscores the potential for human exposure when working closely with infected animals, though public health officials currently assess the risk to the general public as low.
The confirmed cases are among farm workers involved in the process of depopulating poultry – culling infected birds to prevent further spread of the disease – at the affected facility. A CDC team is currently on the ground in Colorado, providing support to state and local health officials in assessing the outbreak and monitoring the health of those potentially exposed. The situation highlights the ongoing challenges of managing avian influenza, particularly as outbreaks continue to impact both poultry and dairy farms across the country.
Mild Symptoms Reported in Colorado Cases
According to the CDC, all four individuals who tested positive for the H5 virus reported experiencing mild illness. Symptoms included conjunctivitis – inflammation of the eye – and related eye irritation, alongside more typical flu-like symptoms such as fever, chills, coughing and a sore throat or runny nose. Additional cases are possible as ongoing monitoring and testing continue among workers at the facility. The CDC is actively monitoring these developments and will provide updates as new information becomes available.
This marks the first instances of H5 virus infection in poultry workers in the United States since 2022, when the first U.S. Case in a poultry worker was reported in Colorado during April of that year. Colorado previously reported a case of H5 in a dairy worker on July 3, 2024, indicating ongoing outbreaks on both dairy and poultry farms within the state. This dual outbreak scenario presents a complex public health challenge, requiring coordinated efforts between human and animal health officials.
Genetic Sequencing Underway
The precise designation of the influenza virus neuraminidase – the “N” component of the H5 subtype – is currently pending genetic sequencing at the CDC. Scientists are working to analyze clinical specimens to determine the specific strain of the virus and to identify any genetic changes that could potentially alter the agency’s risk assessment. Results from this sequencing are expected within one to two days, according to the CDC. This analysis is crucial for understanding the virus’s behavior and potential for transmission.
Currently, the CDC’s recommendations related to H5 bird flu have not changed. However, the agency will assess the information gathered from these recent cases to determine if any adjustments to the human health risk assessment are warranted. The CDC has deployed a multidisciplinary team of nine people – including epidemiologists, veterinarians, clinicians, and an industrial hygienist – to Colorado to support the public health response. This team is conducting ongoing monitoring of workers and testing additional specimens, continuing a collaborative approach between local, state, and federal public health agencies.
The CDC has more than 170 staff members actively deployed to its H5N1 response efforts nationwide. The agency is committed to providing regular updates as the situation evolves. For the latest information on avian influenza, the public can visit the CDC’s avian influenza website.
Disclaimer: This information is intended for general knowledge and informational purposes only, and does not constitute medical advice. It is essential to consult with a qualified healthcare professional for any health concerns or before making any decisions related to your health or treatment.
The situation in Colorado will continue to be closely monitored, and further analysis of the virus will be critical in understanding the potential for broader transmission. Ongoing vigilance and adherence to public health guidelines remain essential in mitigating the risk of H5 bird flu. Share your thoughts and questions in the comments below.