H5 Bird Flu: 3 New Colorado Cases Bring US Total to 13 | CDC Update

The Centers for Disease Control and Prevention (CDC) has confirmed three additional human cases of highly pathogenic avian influenza (HPAI) A(H5) – commonly known as H5 bird flu – linked to a second poultry farm in Northeast Colorado’s Weld County. This brings the total number of human cases associated with outbreaks in Colorado to nine, and the national total since April 2024 to 13. The cases involve individuals working directly with infected poultry, and all three reported mild illness, receiving offers of the antiviral drug oseltamivir as treatment.

Poultry Worker Exposure and Ongoing Monitoring

These latest confirmations follow the CDC’s earlier reporting of six human cases associated with a different poultry farm in the state. A CDC multidisciplinary field team is currently on the ground in Colorado, supporting state and local health officials in assessing the outbreaks and monitoring the health of potentially exposed individuals. The agency is actively tracking these developments and will provide updates as new information becomes available. The initial cases, announced July 19th and 20th, highlighted the potential for human exposure when working closely with infected animals, though public health officials continue to assess the risk to the general public as low.

The CDC’s current assessment, based on available data, is that the risk to the general public remains low. However, the agency emphasizes the risk is moderate to high for those in direct contact with potentially infected animals or contaminated materials. This underscores the importance of preventative measures, particularly for those working in agricultural settings.

Understanding HPAI A(H5) and Human Infection

Highly pathogenic avian influenza (HPAI) A(H5) viruses are known to circulate globally among wild birds. Outbreaks can occur in poultry, and, as seen recently, in other animals like dairy cows. Human infections are rare, but can happen when someone has close contact with infected birds or other animals. The CDC defines HPAI as a strain of influenza that causes severe disease and high mortality in poultry. More information about HPAI is available on the CDC website.

Prior to 2024, the United States had only reported one confirmed human case of H5N1 bird flu – a poultry worker in Colorado in April 2022. Counting that case, there have been a total of 14 human cases of H5 bird flu in the United States since 2022. This recent cluster of cases, while still limited, is prompting increased vigilance and monitoring.

What the Investigation Reveals So Far

The CDC is actively investigating these cases to understand the transmission dynamics and assess whether any changes in the virus warrant adjustments to public health recommendations. A key focus is determining whether the virus is undergoing genetic changes that could increase its transmissibility between humans. To date, the CDC has not detected such changes, but continuous monitoring is crucial.

The investigation will also examine compliance with recommended personal protective equipment (PPE) protocols among farm workers. Historically, most human cases of bird flu infection have occurred in individuals who were not using appropriate PPE. This highlights the importance of consistent and correct use of protective measures, including respirators, eye protection, and gloves, when working with potentially infected animals.

CDC Recommendations for Prevention

The CDC offers specific recommendations to minimize the risk of H5 bird flu infection. These include avoiding unprotected exposure to sick or dead animals, including wild birds, poultry, and other domesticated animals. It’s also advised to avoid contact with animal feces, bedding, and unpasteurized (“raw”) milk. Detailed interim recommendations for prevention, monitoring, and public health investigations are available on the CDC website.

The CDC also provides updated recommendations for worker protection and the use of personal protective equipment (PPE). Following these guidelines is central to reducing individual risk and containing the overall public health risk. For the general public, the CDC recommends drinking pasteurized milk, as pasteurization eliminates potentially harmful bacteria and viruses. Cooking poultry and meat products to an internal temperature of 165°F and practicing thorough handwashing are also important preventative measures.

Risk Assessment and Context

It’s important to remember that while these cases are concerning, the overall risk to the general public remains low. The cases are concentrated among individuals with direct occupational exposure to infected poultry. The CDC emphasizes that We find no signs of unexpected increases in flu activity outside of these affected farms or states. The agency continues to monitor the situation closely and will adjust its recommendations as needed.

Looking Ahead: Surveillance and Guidance Updates

The CDC’s response to these outbreaks involves ongoing surveillance, investigation, and communication. The agency is working closely with state and local health departments to monitor the situation, track cases, and provide guidance. Analysis of the virus sequences from these outbreaks will be crucial in determining whether a change in the risk assessment is warranted. The CDC will continue to assess the situation and provide updates as new information becomes available. The agency’s recommendations related to H5 virus have not changed at this time, but are subject to revision based on ongoing investigation findings.

The situation highlights the importance of robust surveillance systems and rapid response capabilities in addressing emerging infectious disease threats. Continued vigilance and adherence to public health recommendations are essential in protecting both human and animal health.