CDC A(H5N1) Bird Flu Response Update June 28, 2024

At a glance

CDC provides an update on its response activities related to the multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," in dairy cows and other animals in the United States.

CDC Update

June 28, 2024 – CDC continues to respond to the public health challenge posed by a multistate outbreak of avian influenza A(H5N1) virus, or "H5N1 bird flu," 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. To date, there have been three human cases associated with an ongoing multistate outbreak of A(H5N1) in U.S. dairy cows. A Based on the information available at this time, CDC's current H5N1 bird flu human health risk assessment for the U.S. general public remains low. All three sporadic cases had direct contact with sick cows. On the animal health side, USDA is reporting that 132 dairy cow herds in 12 U.S. states have confirmed cases of avian influenza A(H5N1) virus infections in dairy cows as the number of infected herds continues to grow.

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

  • Posting the CDC H5N1 Science Agenda that summarizes the key research issues that the agency hopes to address related to the ongoing outbreak of A(H5N1) virus in dairy cows and other animals in the United States.
  • Posting updated recommendations for agricultural fair organizers and people exhibiting animals at agricultural fairs on how to reduce the risk of novel influenza A viruses spreading between animals and people at these events. These recommendations, which previously focused on reducing the risk of spreading swine-origin flu viruses between pigs and people, have been expanded to include cattle, given the ongoing outbreak of H5N1 bird flu in U.S. poultry and cattle. Millions of people in the United States attend agricultural fairs each year, usually in the summer season. When large numbers of animals and people are in close contact with each other, this raises the risk of disease spread. Measures to reduce the risk of infection include avoiding animal exposures, which is especially important for people who are at higher risk of developing serious flu complications, and frequent handwashing. Read the updated documents: Considerations and Information for Fair Exhibitors to Help Prevent Influenza and Considerations and Information for Fair Organizers to Help Prevent Influenza.
  • The Michigan Department of Health and Human Services (MDHHS) launched an H5N1 bird flu seroprevalence study of individuals exposed to sick cows. The study aims to determine if there has been asymptomatic infection with H5N1 bird flu among people who have worked with sick cows, if certain jobs might increase risk of exposure, and how personal protective equipment (PPE) can protect against infection. CDC is providing technical assistance.
  • Continuing to support strategies to maximize protection of farm workers, who are at higher risk of infection based on their exposures. This includes outreach to farm workers in affected counties through Meta (Facebook and Instagram), digital display, and audio (Pandora). These resources provide information in English and Spanish about potential risks of A(H5N1) infection, recommended preventive actions, symptoms to be on the look-out for, and what to do if they develop symptoms. Since May 30, when English assets launched, Meta outreach has generated more than 4.5 million impressions. Spanish Meta assets launched on June 6, and since then have garnered 650,000 impressions. Additionally, CDC continues to create additional materials, including fact sheets in K'iche' and Nahuatl, in addition to Spanish.
  • Continuing to work with public health laboratories to monitor influenza virus testing. While 53 people have been tested for A(H5N1) virus associated with the dairy cow outbreak, it is important to look at exposure-based testing in the context of CDC's wider testing for flu in the United States. Since March 3, 2024, 31,223 specimens have been tested by public health laboratories for flu with results being reported to CDC. These were specimens submitted to public health laboratories for flu testing and subtyping as part of regular flu surveillance activities. Public health laboratories report data to CDC each week, and more than 200,000 specimens are tested each year. These laboratories use a testing protocol that would detect A(H5N1) virus and other novel viruses. Among those more than 30,000 specimens tested since March 3, 2024, no cases of H5N1 bird flu were detected.
CDC conducts laboratory work on influenza viruses year-round.
CDC conducts laboratory work on influenza viruses year-round.

CDC Yearly Lab Work on Flu Viruses

1,600,000: More than 1.6 million patient specimens are tested in clinical labs participating in CDC domestic disease surveillance.*

200,000: More than 200,000 specimens are tested in 93 state/local public health labs.

6,000: CDC conducts full genetic sequencing on about 6,000 flu viruses each year.

3,000: CDC tests more than 3,000 flu viruses to determine their immune properties.

60: CDC prepares more than 60 viruses for possible use in vaccine production.

*Numbers represent average annual data as reported to CDC's Influenza Division from 2015-2022, excluding the 2020-2021 season when there was little influenza activity.

  • 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 780 people have been monitored as a result of their exposure to infected or potentially infected animals, and at least 53 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. More information on monitoring can be found at Symptom Monitoring Among Persons Exposed to HPAI.
  • Continuing to monitor flu surveillance data using CDC's enhanced, nationwide summer surveillance strategy, 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.

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.

  1. The first human case of H5N1 bird flu linked to an outbreak in dairy cows in the United States was reported on April 1, 2024, in Texas. It was also likely the first human infection with avian influenza A(H5N1) virus from a cow globally. A second human case associated with the dairy cow outbreak was identified in Michigan on May 22, 2024. A third human case associated with the dairy cow outbreak was identified in Michigan on May 30, 2024. None of these three cases are associated with the others. These cases were actually the second, third, and fourth human cases of H5N1 bird flu ever reported in the United States. The first human case of H5N1 bird flu in the United States was reported on April 28, 2022, in a person in Colorado who had direct exposure to poultry and who was involved in depopulating poultry with presumptive H5N1 bird flu. The 2022 human case was not related to dairy cattle. The person only reported fatigue without any other symptoms and recovered.