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More and more cows in Colorado are falling ill with bird flu. Authorities are trying to prevent the spread to humans.
More and more cows in Colorado are falling ill with bird flu. Authorities are trying to prevent the spread to humans.

Colorado Public Radio originally published this story on June 21, 2024 at 6:20 p.m.

Cases of highly pathogenic avian influenza in cows are on the rise in Colorado, and state officials told CPR on Friday that they are working with the dairy industry to contain the spread.

The first case in dairy cows in the state occurred in April. Since then, 18 more cases have been reported. Colorado recorded 15 cases this month alone and added six more cases on Friday to a state website that tracks positive cases in dairy cows.

All confirmed cases occurred in northeast Colorado.

According to a U.S. Department of Agriculture website, a total of ten cattle herds in Colorado, mostly dairy cows, were affected in the last 30 days (as of mid-week).

Dr. Rachel Herlihy, the state’s epidemiologist, said the risk “remains low for humans and depends on exposure.”

She said the state is working closely with the agricultural industry and affected farms to ensure workers are monitored and have access to testing and treatment if needed.

“Although cases are increasing here in Colorado,” Herlihy said, “we are working closely with our dairy industry and many other partners to contain the further spread of the virus here in the state.”

“Implementing really good biosecurity will be one of our most important ways to stop and prevent the further spread of this virus on additional dairy farms,” said Dr. Maggie Baldwin, Colorado State Veterinarian.

Biosecurity measures include isolating infected cattle, checking the cleanliness of cow feed and regularly cleaning water supplies.

Earlier this week, Colorado released guidelines for livestock owners and event organizers in advance of the upcoming fair season this summer.

The state is providing personal protective equipment (PPE) to dairy workers. Any place with a confirmed case will be quarantined to restrict the movement of dairy cows in milk production and must take measures to limit the possibility of the virus spreading.

The virus has been spreading in the United States since spring 2022. Initially, it was mainly found in infected waterfowl and domestic poultry. This year, however, it began to affect another important livestock: cows.

The first case in a Colorado cattle herd occurred on April 25, when the National Veterinary Services Laboratory announced it had discovered the disease among dairy cows in northeastern Colorado.

In the last 30 days, the US Department of Agriculture (USDA) has identified 59 confirmed cases of bird flu in cows in eight states. Colorado and Michigan each reported ten affected livestock; only Idaho had more cases, with 17.

According to a spokesman for the state health department, cows in herds that show clinical signs of the virus will be separated from the rest of the herd until they recover.

The quarantine applies to all dairy cows on the property and will remain in effect until the dairy receives two negative tests one week apart. Additionally, all dairy cows in Colorado are covered by an emergency rule passed on April 30 that requires mandatory testing for dairy cows being moved to other states.

Baldwin said the state is closely monitoring the situation.

“One of the good things is that here in the state of Colorado, we always take a risk- and science-based approach to everything we do,” she said. “So if there’s a change in the risk or threat of disease transmission, whether it’s within the same species or a different species, we’re always able to adjust our response, be nimble and flexible and bring in the right partners.”

Herlihy said the state is providing training and education to dairy workers, including on the proper use of personal protective equipment.

“The risk of infection is low, but we know it will be higher in people who have regular contact with the virus on affected dairy farms,” ​​she said.

The state monitors individuals on the affected farms and works closely with the producers and foremen of these farms.

“If individual people develop symptoms, they are reported to us. We coordinate testing for these people and also coordinate treatment,” Herlihy said.

A worker in Texas and two in Michigan tested positive for the virus earlier this year, but no cases have been recorded in Colorado. The CDC said last month after the second case in Michigan that the risk to the public remains low “because all three sporadic cases had direct contact with infected cows.”

Information for consumers and veterinarians

The increasing number of cases raises questions about the risk avian flu poses to humans and concerns about the safety of many common foods.

Colorado’s website provides information for both consumers and veterinarians.

It notes that both the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA) have stated that there are currently “no concerns about the safety” of the commercial milk supply because commercial dairy products are pasteurized before sale.

According to the website, pasteurized milk does not pose a risk to the health of the consumer. Pasteurization has been consistently proven to inactivate bacteria and viruses in milk.

Despite the discovery of the virus in dairy cows, the risk to the general population remains low, according to the CDC. For more information on the current situation regarding H5N1 avian influenza, visit the CDC website.

Veterinarians in Colorado must report illnesses in cattle exhibiting clinical signs of highly pathogenic avian influenza to the state veterinary office at (303) 869-9130 using the Illness Reporting Form or to their local veterinary office. Veterinarians may request HPAI testing for samples that meet the criteria.

By Everly