July 12, 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. Four human cases of A(H5) infection associated with this outbreak in U.S. dairy cows have been reported. 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. On the animal health side, USDA is reporting that 151 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:

Reporting that despite extensive efforts, CDC has been unable to sequence or isolate virus from the recent human case in Colorado. Attempts to sequence viral RNA from the Colorado case were unsuccessful most likely due to insufficient virus in the clinical sample. As a result, CDC has not been able to conclusively determine the neuraminidase (NA) subtype of the virus. Given that cows on the farm where the patient worked were confirmed positive for A(H5N1) virus infection, it is likely this was an N1 also, but that cannot be conclusively demonstrated. Virus isolation attempts in eggs and cells were similarly unsuccessful.
Continuing to meet with commercial laboratories to discuss H5 assay licensing agreements and interest in development of commercial H5 tests. CDC’s Technology Transfer Office and the Influenza Division are actively pursuing establishing licensing agreements with multiple companies, and several have been completed. Eight of those licenses are currently in place, and several more are in progress.
Posting a flyer that describes and illustrates the procedure for collecting, storing, and shipping conjunctival specimens for testing using the Influenza A(H5) assay. This resource can help staff at clinics or hospitals and public health departments collect specimens using eye swabs to test for the presence of A(H5) virus.
Posting an NCIRD Bulletin on the updated CDC agricultural fair guidance.
Testing the serological specimens collected as part of the Michigan farmworker investigation is ongoing. Results are expected by mid-July.
Planning a Clinician Outreach and Communication Activity (COCA) Call on July 16, 2024, that will give an update on the current outbreak in the United States and current CDC surveillance and monitoring efforts. Speakers will also provide information for clinicians on testing, using antivirals, and infection prevention and control recommendations.
Continuing to support strategies to maximize protection of farm workers, who are at higher risk of infection based on their exposures. This includes targeted 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 7.6 million impressions. Spanish Meta assets launched on June 6, and since then have garnered 1.1 million impressions. (Table 1)
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 1,390 people have been monitored as a result of their exposure to infected or potentially infected animals, and at least 61 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. Since March 24, 2024, more than 32,000 specimens have been tested at public health labs that would have detected influenza A(H5) or other novel influenza viruses. 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.