What to know about bird flu: CSU expert discusses the virus’ impact

Media contact: Jennifer Dimas
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A highly pathogenic version of avian influenza virus, commonly referred to as bird flu, was detected in wild birds in the United States in early 2022. In spring 2024, multiple states, including Colorado, began reporting outbreaks in dairy cattle, a concerning development because the virus was circulating in a new species.

Testing is critical to controlling spread of the virus, and Colorado State University’s Veterinary Diagnostic Laboratory, or VDL, is playing a key role, regularly testing samples from birds, cattle and other species. Understanding how disease is affecting wild and domestic animals is a mission of the lab in Fort Collins, and that information is essential for animal and public health officials, food-animal producers and others to respond effectively to halt the spread of disease and curb potential impacts to human health.

Domestic cats

Recently, the lab has been detecting this version of avian influenza virus in domestic cats. “In Colorado, we’ve detected a lot of cat positives,” said Dr. Kristy Pabilonia, executive director of the VDL. “Understanding the spread of the virus in cats has been one of our focuses. It’s very concerning because these are people’s pets.”

Avian influenza viruses have been detected for decades in wild waterfowl and shorebirds, such as ducks and geese. These birds are considered the “reservoir species” for the virus, hosts that harbor and transmit the pathogen. Some influenza viruses, however, can spill over and infect other populations. The current H5N1 virus, scientifically known as H5N1 clade 2.3.4.4b, can infect wild birds, domestic poultry and mammals, including humans.

Commercial poultry operations

Commercial poultry operations have been hit particularly hard. Producers have lost entire flocks to the virus due to high mortality and culling, a response to stop the disease from spreading. In addition to dairy cattle, there have been sporadic infections in other mammals, and, according to the Centers for Disease Control and Prevention, 70 reported cases in humans since April 2024, including one death. The human cases have been the result of people interacting with infected animals, according to the CDC.

Since the dairy cattle outbreaks began last spring, the CSU laboratory has been testing samples daily, running as many as 600 samples on a busy day. The lab works closely with state and federal agencies, including the Colorado Department of Agriculture, Colorado Parks and Wildlife and the Colorado Department of Public Health and Environment on testing submissions and reporting.

The CSU lab is part of the USDA’s National Animal Health Laboratory Network, a collection of more than 64 public veterinary labs across the country, and it works closely with the network on testing. Read more from Pabilonia about the most recent influenza outbreaks on SOURCE. She is a microbiologist, veterinarian and an expert on poultry diseases. Pabilonia has dedicated a large portion of her career to studying avian influenza viruses.

For more information read the Q & A with Dr. Pabilonia.