Colorado officials have announced a total of five people have tested positive for highly pathogenic avian influenza (HPAI), even as the Oklahoma Department of Agriculture, Food and Forestry (ODAFF) reported its first case of HPAI in cattle.

Specimens from the Colorado human cases were sent to the Centers for Disease Control and Prevention (CDC) for confirmatory testing. CDC confirmed four of the cases, and one additional case is presumptive positive and pending confirmation. All of the people experienced mild symptoms and were workers who were involved in the depopulation of poultry at a poultry facility experiencing an outbreak of the H5N1 virus. At the state’s request, CDC is sending a team to Colorado to support their investigation, which is ongoing.

CDC’s current risk assessment for the general public remains low, however the agency said that human infections of the virus are concerning because of the potential to cause severe disease. The other reason these types of human infections are concerning is because of their pandemic potential, it added. “If these viruses were to change to spread easily from person-to-person, it could trigger a pandemic, though, to date, we have not seen genetic changes in the virus that would make it more likely to transmit between humans.”

CDC outlined the following prevention recommendations:

Oklahoma dairy herd tests positive

In Oklahoma, ODAFF relayed that a positive cattle sample was collected by a dairy in April and recently submitted to USDA Animal and Plant Health Inspection Service (APHIS) for testing. Because of the time lapse, the dairy herd has fully recovered, and the farm has not reported any other cases of HPAI, ODAFF noted.

Further, the agency said there is no concern about the safety of pasteurized milk or dairy products. The commercial milk supply remains safe due to both federal animal health requirements and pasteurization.

Oklahoma is the 13th state to have a confirmed positive case of HPAI in a dairy herd.

“We have been monitoring detections of HPAI in other states since the first detection in March,” said Oklahoma State Veterinarian Dr. Rod Hall. “Our team has been in constant communication with Oklahoma dairies asking them to heighten their biosecurity practices. PPE has also been made available to Oklahoma dairy farmers.”

More information on HPAI in dairy cattle, including recommended biosecurity measures, can be found on the ODAFF Disease Alerts page.

USDA data shows a total of 158 livestock herds have been affected by the virus since late March, while a total of 23.3 million birds have been affected since the virus was first detected in February 2022.