Influenza A (H5N1) in Cattle

What is Influenza A or H5N1?

Influenza A infection is uncommon in cattle. The current dairy cattle infections have occurred from an influenza A strain, H5N1, that had previously been the cause of illness primarily in wild birds, domestic turkeys and chickens, and occasionally other mammals. You may have heard it referred to as Highly Pathogenic Avian Influenza or HPAI because of severe infections in birds, or more recently Bovine Influenza A Virus (IAV-B).

What is the concern?

The influenza A/H5N1 virus was not known to cause infection in cattle until March 25, 2024, when it was confirmed in a dairy herd in Texas. A farm worker developed conjunctivitis (redness and swelling of the eye) on March 27, 2024, which is the first reported human infection following contact with an infected dairy herd. The influenza A/H5N1 virus has not been identified to transmit from human to human, but there appears to be a low risk of human infection among those with close contact with dairy cattle infected with the influenza A/H5N1 virus.

What action(s) should I take?

The situation is still evolving, but the overall risk to the general public posed by this virus remains low. Maintain healthy practices, such as avoiding sick or dead animals and avoid consuming unpasteurized (raw) milk or raw cheeses. It is safe to drink commercial milk because products are pasteurized before entering the market. Pasteurization kills bacteria and viruses, like influenza viruses, in milk. CDC has additional guidance available here.

What are the symptoms of influenza A/H5N1 virus infection?

Conjunctivitis (redness and swelling of the eye) appears to be the main symptom of Influenza A/H5N1 virus infection. Other symptoms typical of influenza infection include cough, fever or feeling feverish, sore throat, runny nose, fatigue, headache, muscle or joint aches, and shortness of breath or difficulty breathing.

What can medical providers do?

Medical providers should remain vigilant for a patient with both (1) direct contact or consumption of H5N1-infected birds, animals, or their raw food/dairy products, and (2) signs/symptoms of influenza infection. If a patient meets both criteria, isolate the patient and follow infection control recommendations, notify the South Dakota Department of Health by calling 800-592-1861, collect specimens for testing at the South Dakota Public Health Laboratory, and begin antiviral medication treatment with oseltamivir (twice daily for five days) regardless of time since symptom onset. Additional guidance can be found here.

What can Farmer, Rancher, and other Animal Caretakers do?

To reduce the risk of influenza A/H5N1 virus infection, avoid unprotected direct physical contact or close exposure with sick or dead birds or other animals, and avoid consuming raw (unpasteurized) milk or other raw dairy products. When in contact with sick or dead birds or other animals, wear personal protective equipment (PPE). CDC has additional guidance available here.

H5N1 Virus Guidance for Farm Workers

Guía sobre el virus H5N1 para trabajadores agrícolas

Protect Yourself From H5N1 When Working With Farm Animals (CDC)