Commonground
Senior Moderator
May 3, 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. Currently, one human case has been confirmed in a person with exposure to presumably infected dairy cows reported by Texas on April 1, 2024[SUP] [1][2][/SUP].
CDC’s response to this outbreak of influenza A(H5N1) virus in dairy cattle and other animals most recently includes:
CDC’s response to this outbreak of influenza A(H5N1) virus in dairy cattle and other animals most recently includes:
- 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. Testing of symptomatic people who have exposures is being done by state or local officials, and CDC is conducting confirmatory testing when needed.
- Monitoring and testing data are now being reported, and will be updated weekly on Fridays. Since March 2024, at least 220 people have been monitored for A(H5N1) after relevant exposures and at least 30 people have been tested.
- Having ongoing discussions with multiple states about state-led field investigations to explore key scientific and public health questions related to the ongoing outbreak. CDC is playing a coordinating role with regard to investigation protocols so that data collection can be standardized across states and results can be pooled. In addition, CDC has multilingual and multidisciplinary epidemiological field teams ready to deploy to support on-site studies if requested.
- Continuing work to better characterize the virus from the human case in Texas.
- Beginning cell and animal laboratory studies, including to:
- Learn how the virus reproduces in both human and cow respiratory tract epithelial cells and cow mammary epithelial cells.
- Assess the severity of illness and transmissibility of the virus under different scenarios by infecting ferrets and assessing the outcome. Ferrets are used as a model for people because they get sick and spread influenza viruses in a manner similar to humans.
- Beginning cell and animal laboratory studies, including to:
- Testing human sera (blood) from people previously vaccinated with pre-pandemic A(H5) vaccines during clinical trials to see how their antibodies cross-react to the virus isolated from the human case in Texas. Data to date – including genetic analysis and testing of ferret antisera from multiple clade 2.3.4.4b candidate vaccine viruses (CVVs) (Reference table below[SUP][3][/SUP]) – suggest vaccination will offer good cross-protection against cattle outbreak viruses. (The human case in Texas was a 2.3.4.4b virus). Antigenic characterization of the virus isolated from the human case in Texas (A/Texas/37/2024) with ferret antisera produced against existing pre-pandemic CVVs confirmed clade 2.3.4.4b A(H5) CVVs have good cross-reactivity to this virus.
- Engaging with manufacturers of commercial diagnostic tests and clinical partners to make progress toward the goal of having an A(H5N1) test that is widely available for consumers.
- Working so that states can conduct A(H5N1) testing on eye specimens. This week, use of eye swabs with the CDC H5 assay was approved by the CDC Clinical Laboratory Improvement Amendment (CLIA) director for use at CDC, which means results can be reported back for patient care. Originally, the A(H5N1) test was designed for use with respiratory specimens.
- Developing information for health care provider organizations to share with their membership related to the health concerns around consumption of raw milk in the context of the current A(H5N1) outbreak, since A(H5N1) virus fragments have been detected at high levels in raw milk. CDC and FDA recommend against the consumption of raw milk. Testing at FDA has indicated that pasteurization kills A(H5N1) virus in milk.
- Continuing to engage One Health partner organizations from public health, agriculture, wildlife, milk regulatory officials, and others to share information and ensure preparedness to prevent and respond to this emerging infectious disease threat and for any potential human infections.
- Continuing to monitor flu surveillance data, especially in areas where A(H5N1) viruses have been detected in dairy cattle or other animals, for any unusual trends in flu-like illness, flu, or conjunctivitis.
- CDC maintains a webpage on How CDC is monitoring influenza data to better understand the current avian influenza A (H5N1) situation in people that is updated weekly.
- CDC flu surveillance systems show no indicators of unusual flu activity in people, including avian influenza A(H5N1) viruses, for the most recent week.