Will another bird flu epidemic hit Colorado? Too early to tell.

Ducks returning to Barr Lake State Park in Brighton Colorado. A few days ago, a ranger there related that to date (October 29 ,2025) there are no indications of bird flu among these migrating birds.

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Walking along the South Platte River just north of 88 Ave in Brighton, north of Denver. I came across a dead mallard on the river’s far bank. It worried me. Not far from that spot, a year ago, I saw a red-tailed hawk pecking away at a dead duck on a walking path, the site of which gave me chills. Of course, neither that encounter or the more recent sighting of a dead duck indicate bird flu, but I admit, both incidents made me somewhat apprehensive. Victims of bird flu? Or not.

Although recent reports suggest that bird flu, formally labeled avian influenza (Highly Pathogenic Avian Influenza or HPAI) started to intensify in northern states in the Midwest a month ago; to date (November 1, 2025), to date it has hardly hit Colorado either in wild or domesticated birds, at least not yet. Cases were down both nationally and in Colorado during the summer, but what might happen now and, in the future, remains unknown.

Still bird flu is a global issue. As the Center of Disease Control notes, it is widespread in wild birds worldwide and is causing outbreaks in poultry and U.S. dairy cows with several recent human cases in U.S. dairy and poultry workers. A number of mutations of the original flu have facilitated first a jump from wild to domesticated birds, with a few forms jumping to humans as well although those viruses, to date at least, have not spread from human to human as of yet.

Here in the United States some 70 confirmed cases have been reported as has one death. 41 of these came from contact with dairy cattle, 24 with poultry farms and culling operations, 2 from other animals (backyard flocks, wild birds or other mammals) and one from unknown exposure. The worst effected states are Washington and California, but Colorado is not far behind with ten human cases most of which came from contacts with poultry farms. The latest information about bird flu in humans includes the fact that influenza may infect GI tracts and cause “digestive symptoms“. Last year the worst month for infections nationwide was January 2025.

During the first eight months of 2025, between January 1 and August 4, 2025, worldwide, 26 human infections with avian influenza A(H5N1) viruses (H5 bird flu) have been detected globally, of which 23 were identified in 7 countries outside of the United States, including 11 infections that resulted in death. Three of these cases were reported in the USA, all prior to mid-February, 2025. The 11 deaths occurred in Cambodia ((8), India (2) and Mexico (1). All of these were in people in contact with poultry or wild birds. In all these cases no person-to-person spread was noted; such a development is most feared and thus monitored. The genetic strain of bird flu is H5N1; however, this virus has mutated into a second strain H5N2 as it is referred to; this latter virus can change the way the virus behaves in an animal species. Bird flu has already mutated so that there are cases of the condition jumping to humans on a limited scale but at least to date, data suggests that we humans do not transfer it from one person to another. Could happen though.,

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As the annual bird migration season is coming to an end this prognosis could easily change.  So far, only a few alarms have been sounded. An earlier report from the Rocky Mountain Raptor Program on Facebook painted a worrying picture of the disease’s spread:

HPAI has returned to the lower 48 with the Fall migration and cooler temperatures but earlier and at a level that previously was not seen during this time of year. (“this time of year” being late September/early October)

That same report focused on the condition in wild birds nationally and noted:

There have been multiple positive detections in wild birds (live and dead) across the northern tier states from Idaho and Utah to the East coast. Commercial and backyard poultry flocks have also been hit. Commercial poultry facilities in North and South Dakota, Minnesota, Wisconsin and Michigan have been hit to the tune of almost 600k birds and the numbers are growing. In previous years the Fall outbreaks primarily followed the coasts. This broad swath across the country speaks to the potential of wider spread of asymptomatic infection in migrating and local birds.

Although I could not find much information at Colorado State websites, the same Rocky Mountain Raptor Report noted that a number of bird flu cases it has processed. These included autopsies on a Great Horned Owl and an infected turkey vulture, both around Loveland Colorado, some 60 miles north of Denver on Colorado’s Front Range just east of the Rockies. The most recent outbreak in Colorado, at the beginning of the year, was in the north central part of the state (around Ft. Collins and Greeley). While I could find no evidence of the condition in domesticated ducks and geese as of yet in the state. Over the 2022-3 winter the state had to euthanize 6.5 million domesticated fowl as the flu jumped from wild to domesticated bird species with a vengeance leading to a spike in egg and chicken prices at the time.

Given how widespread bird flu has become globally,

October 12, 2025 on the South Platte River north of 88 Ave in Thorton