CDC A(H5N1) Bird Flu Response Update – September 27, 2024: What You Need to Know

In this week's update, the Centers for Disease Control and Prevention (CDC) released important information regarding the ongoing avian influenza A(H5N1) bird flu outbreak affecting the United States. This update covers the ongoing investigation in Missouri, newly updated guidance on the use of personal protective equipment (PPE) for those working with or exposed to infected animals, and new standardized protocols for subtyping wastewater samples testing positive for the influenza A virus. Here’s what you need to know.

Situation Update

As of September 27, 2024, the CDC continues to respond to a widespread multistate outbreak of avian influenza A(H5N1) virus, commonly referred to as bird flu. The outbreak has primarily impacted dairy cows, poultry, and other animals across the U.S. Since the first case was reported in April 2024, the CDC has been working closely with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), and state public health officials. Using a "One Health" approach, these agencies collaborate to manage the outbreak across both human and animal health sectors.

To date, 14 human cases of avian influenza virus infection have been confirmed in the United States. These infections have been traced to two main sources: exposure to infected dairy cows (four cases) and exposure to poultry infected with the H5N1 bird flu virus (nine cases). The most recent case, reported in Missouri on September 6, remains under investigation, with the exact source of exposure still unknown. Despite these cases, the CDC reassures that the overall risk to the general public remains low.

Missouri Case Update

Missouri has been at the center of attention in recent weeks due to the state’s only reported case of H5 bird flu, first identified on September 6, 2024. The Missouri Department of Health and Senior Services, in coordination with the CDC, has been actively investigating this case and closely monitoring anyone who had close contact with the infected individual.

Among the health care workers who were exposed to the infected patient, 18 were categorized as having high-risk exposure, while 94 had lower-risk exposure. Two health care workers with higher-risk exposure developed mild respiratory symptoms, with one testing negative for influenza by PCR. Several others have provided blood specimens to be tested for potential H5 antibodies.

Though the investigation continues, no signs of ongoing transmission have been identified. To date, no contacts of the infected individual have tested positive for the bird flu virus, and the case remains isolated.

Animal Health Impact

On the animal side, the USDA has reported that 238 dairy herds across 14 states have confirmed infections with the H5N1 bird flu virus in dairy cows. These numbers are part of a growing trend of infections in the agricultural sector. Since April 2024, a total of 36 commercial poultry flocks and 23 backyard flocks have been affected by the virus, with approximately 18.75 million birds impacted nationwide.

The CDC and USDA stress the importance of containing the spread of avian influenza within animal populations, as this is key to preventing further human exposure to the virus.

New Protocol for Wastewater Testing

In a significant step forward, the CDC has developed a standardized protocol for subtyping wastewater samples that test positive for influenza A. This protocol includes specific primers and probes that allow for the identification of various influenza subtypes, including H5N1. This new tool enables partner laboratories to better detect and report bird flu virus activity in wastewater samples, helping public health officials track and respond to outbreaks more effectively.

Updated Personal Protective Equipment (PPE) Guidance

To further protect individuals working with or exposed to infected animals, the CDC has issued updated PPE guidance. The new recommendations are aimed at reducing the risk of avian flu transmission to workers, particularly those handling animals infected with the H5N1 bird flu virus. This includes guidance for occupational groups who may be at higher risk of exposure, such as farm workers, veterinarians, and animal health officials.

Employers are urged to implement additional control measures and ensure that workers use appropriate PPE, especially when handling infected or potentially infected animals. Heat stress, a common concern when using PPE in hot environments, is also addressed in the new guidelines.

A newly introduced hazard assessment worksheet can help employers in dairy facilities and other agricultural settings determine when and how to implement these protective measures. Additionally, fact sheets and educational materials have been developed to help workers use PPE safely and effectively.

Outreach Efforts to Farm Workers

The CDC continues to prioritize outreach to farm workers, particularly those working in areas affected by the H5N1 bird flu virus. This outreach is conducted through social media platforms like Facebook and Instagram, as well as digital audio platforms such as Pandora. The CDC is also utilizing local radio stations, broadcasting critical information in English and Spanish to ensure a wide reach.

These messages focus on raising awareness of the risks associated with bird flu virus exposure, symptoms to watch for, and preventative actions workers can take to protect themselves. Additionally, the CDC is promoting free seasonal flu vaccinations for livestock workers in affected areas.

Surveillance and Monitoring

Since the outbreak began, more than 5,000 people have been monitored due to their exposure to infected animals. Of those, at least 240 people who developed flu-like symptoms were tested for bird flu. To date, no additional human cases have been confirmed beyond the 14 reported earlier in the year. The CDC also supports testing efforts at public health labs across the country, where more than 50,000 specimens have been analyzed as part of routine surveillance for novel influenza viruses, including avian influenza A(H5N1).

At the same time, the CDC continues to monitor flu activity across the country. Enhanced surveillance systems are in place, especially in areas where avian influenza viruses have been detected in animals. So far, no unusual influenza activity has been reported in humans, and no signs of widespread transmission of the H5N1 bird flu virus have emerged.

CDC Recommendations

The CDC recommends that individuals avoid exposure to sick or dead animals, particularly wild birds, poultry, and other domesticated animals. People should also avoid direct contact with animal waste, bedding, and unpasteurized milk from animals suspected or confirmed to have avian flu. Infected dairy cows, poultry, and wild birds pose the highest risk for bird flu virus transmission.

For those working closely with animals, including farm workers and veterinarians, wearing appropriate PPE is crucial in preventing exposure. Employers should ensure that workers are equipped with the proper protective gear and follow the updated guidelines to reduce the risk of transmission in the workplace.

Conclusion

The avian influenza A(H5N1) bird flu outbreak remains a serious public health challenge, but thanks to the ongoing efforts of the CDC, USDA, and public health officials, the situation is being carefully monitored and managed. While the risk to the general public remains low, continued vigilance and strict adherence to safety protocols are essential to keeping the outbreak contained.

This is an evolving situation, and the CDC is committed to providing timely updates as more information becomes available. Stay informed about the bird flu virus, and follow the CDC’s recommendations to help protect yourself and others from the H5N1 bird flu virus.

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