CDC A(H5N1) Bird Flu Response Update May 31, 2024

CDC A(H5N1) Bird Flu Response Update

May 31, 2024 - CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or "A(H5N1) virus," in dairy cows and other animals in the United States. CDC is working in collaboration with the U.S. Department of Agriculture (USDA), the Food and Drug Administration (FDA), state public health and animal health officials, and other partners using a One Health approach. On May 30, 2024, CDC reported that an additional human case of highly pathogenic avian influenza (HPAI) A(H5) virus infection was identified in Michigan. This is the third human case associated with an ongoing multistate outbreak of A(H5N1) in U.S. dairy cows. A As with the previous two cases (one in Texas, one in Michigan), the person is a dairy farm worker who had exposure to sick cows, making this another instance of likely cow-to-person spread. Based on the information available at this time, this case does not change CDC's current A(H5N1) bird flu human health risk assessment for the U.S. general public because all three sporadic cases had direct contact with infected cows. On the animal health side, USDA is reporting that 68 dairy cow herds in nine U.S. states have confirmed cases of A(H5N1) virus infections in dairy cows.

Among other activities previously reported in past spotlights and still ongoing, recent highlights of CDC's response to this include:

• Continuing work in the laboratory to characterize the virus from the second human case from Michigan. This includes:
  • Conducting additional sequence analysis. Genetic sequence data from the most recent Michigan specimen confirmed this is a highly pathogenic avian influenza A(H5N1) virus belonging to clade 2.3.4.4b. If more complete sequence data can be generated, it will be compared to previous human cases and dairy cows.
  • Attempting to isolate the virus in the specimen from the most recent Michigan case.
• Providing technical assistance to Michigan Department of Health and Human Services as the department plans to launch a serology epidemiology study of people exposed to sick cows.
• Posting a surveillance strategy for enhanced, nationwide summer monitoring to help ensure that even rare cases of A(H5N1) virus infection in the community are detected. This plan includes:
  • Increasing the number of influenza virus specimens that are tested and then subtyped in public health laboratories, which can detect A(H5). While influenza testing typically declines over the summer, this approach would maintain an increased level of testing.
    • Specifically, jurisdictions were asked to work with clinical laboratories to increase submissions of positive influenza virus samples to public health laboratories for subtyping.
    • CDC is also working with commercial laboratories to increase submission of influenza-positive test specimens to public health laboratories with the aim of increasing the number of specimens available for virus subtyping.
  • Continuing surveillance for laboratory-confirmed, flu-related hospitalizations during the spring and summer through the Influenza Hospitalization Surveillance Network (FluSurv-NET), which typically pauses surveillance activities from May through September.
  • CDC also is working with state and local public health partners to increase outreach to health care providers and clinics to raise awareness about A(H5N1), so that novel flu is considered in patients with conjunctivitis or respiratory illness after relevant exposures.
• Continuing to support strategies to maximize protection of farm workers, who may be at higher risk for infection than others in the population. This week, CDC launched targeted social media outreach to farm workers in affected communities to raise awareness about the potential risk of working with infected or potentially infected animals, including dairy cows, and measures they should take to reduce their risk or if they develop symptoms after exposure.
• Continuing to support states that are monitoring people with exposure to cows, birds, or other domestic or wild animals infected, or potentially infected, with avian influenza A(H5N1) viruses. To date, more than 390 people have been monitored as a result of their exposure to infected or potentially infected animals, and at least 44 people who have developed flu-like symptoms have been tested as part of this targeted, situation-specific testing. Testing of exposed people who develop symptoms is happening at the state or local level, and CDC conducts confirmatory testing as needed.
• Continuing to monitor flu surveillance data, especially in areas where A(H5N1) viruses have been detected in dairy cows or other animals for any unusual trends, including in flu-like illness, conjunctivitis, or influenza virus activity.
  • Overall, for the most recent week of data, CDC flu surveillance systems show no indicators of unusual flu activity in people, including avian influenza A(H5N1) viruses.

Publication Highlights

Also, of note this week:

• A new CDC report, published on May 26, 2024 in the journal Influenza and Other Respiratory Viruses, reports that existing flu surveillance in health care settings in the United States would likely detect at least one case of novel influenza virus infection in people, even when the virus has yet to spread widely. This study underscores the critical role health care providers play as a first line of defense by maintaining the rates of testing for flu performed during the flu season and forwarding clinical specimens to public health laboratories for further testing as recommended.

CDC Recommendations

As a reminder, CDC recommends that:

• People should avoid exposures to sick or dead animals, including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cows), if possible.
• People should also avoid exposures to animal poop, bedding (litter), unpasteurized ("raw") milk, or materials that have been touched by, or close to, birds or other animals with suspected or confirmed A(H5N1) virus, if possible.
• People should not drink raw milk. Pasteurization kills A(H5N1) viruses, and pasteurized milk is safe to drink.
• People who have job-related contact with infected or potentially infected birds or other animals should be aware of the risk of exposure to avian influenza viruses and should take proper precautions. People should wear appropriate and recommended personal protective equipment when exposed to an infected or potentially infected animal(s). CDC has recommendations for worker protection and use of personal protective equipment (PPE).
• CDC has interim recommendations for prevention, monitoring, and public health investigations of A(H5N1) virus infections in people.

Following these recommendations is central to reducing a person's risk and containing the overall public health risk.

In addition to limiting interactions between infected animals and people, containing the outbreak among animals also is important, which underscores the urgency of the work being done by USDA and animal health and industry partners.

This is a rapidly changing situation, and CDC is committed to providing frequent and timely updates.