Enlarge / Chicken eggs are disposed of at a quarantined farm with bird flu in Israel's northern village of Margaliot on January 3, 2022. (credit: Getty | JALAA MAREY )

The flare-up of highly pathogenic bird flu continues to widen in US livestock after federal officials confirmed last week that the virus has spread to US cows for the first time. The virus has now been detected in dairy cows in at least five states , a single person in Texas exposed to infected cows, and an egg farm in Texas, all spurring yet more intense monitoring and biosecurity vigilance as the situation continues to evolve.

As of Tuesday, seven dairy herds in Texas, two in Kansas, and one each in Idaho, Michigan, and New Mexico had tested positive for the virus. The affected dairy herd in Michigan had recently received cows from one of the infected herds in Texas. It remains unclear if there is cow-to-cow transmission of the flu virus.

The virus—a highly pathogenic H5N1 avian influenza or HPAI—has been devastating wild birds worldwide for the past several years. Throughout the devastating outbreak, the flu virus has spilled over to various species , including big cats in zoos, river otters, bears, dolphins, seals, squirrels, and foxes. While cows were an unexpected addition to the list, federal officials noted last week that affected dairy farms had found dead wild birds on their farms, suggesting that wild birds introduced the virus to the cows, not an intermediate host.

Enlarge (credit: Getty | Peter Cade )

Wild migratory birds likely spread a deadly strain of bird flu to dairy cows in Texas and Kansas, state and federal officials announced this week.

It is believed to be the first time the virus, a highly pathogenic avian influenza (HPAI), has been found in cows in the US. Last week, officials in Minnesota confirmed finding an HPAI case in a young goat , marking the first time the virus has been found in a domestic ruminant in the US.

According to the Associated Press , officials with the Texas Animal Health Commission confirmed the flu virus is the Type A H5N1 strain, which has been ravaging bird populations around the globe for several years . The explosive, ongoing spread of the virus has led to many spillover events into mammals, making epidemiologists anxious that the virus could adapt to spread widely in humans.

Enlarge / A numbered and tagged California Condor in the wild. (credit: Educational Images via Getty )

Early March last year, an endangered California condor—one of less than 350 of its kind surviving in the wild—perched on an Arizona cliff face staring into space for days. It’s probably sick from lead poisoning, thought Tim Hauck, the condor program director with The Peregrine Fund, a nonprofit conservation group helping to reintroduce condors to the skies above Grand Canyon and Zion. These bald-headed scavengers—weighing up to 25 pounds with black-feathered wings spanning nearly 10 feet—often fall victim to lead exposure when they consume the flesh of cows, coyotes, and other large mammals killed by ranchers and hunters firing lead bullets. Listlessness and droopy posture are telltale signs. “We were like, I bet this bird’s got into something bad,” said Hauck.

His team of eight wildlife biologists stationed at Arizona’s scenic Vermillion Cliffs National Monument, 150 miles north of Flagstaff, hoped the ailing condor would glide down off its 1,000-foot sandstone ledge to visit their feeding station, where they could trap it to do a health examination. The Peregrine Fund provides supplemental food for the condors—most of which were raised in captivity and released into the wild—in part so the biologists can easily catch them for regular checkups, provide therapy for lead poisoning , vaccinate against West Nile virus, and update equipment used to track the condors’ whereabouts.

A week later, when the sick bird did finally get trapped at the feeding station, Hauck immediately noticed something he hadn’t seen before in lead-poisoned condors. Its eyes were cloudy, a condition called corneal edema. He consulted with Stephanie Lamb, a veterinarian who volunteers at Liberty Wildlife Center, a Peregrine Fund partner organization in Phoenix. He wanted to know if she thought the condor might be ill from something more worrisome than lead poisoning: highly pathogenic avian influenza, or HPAI, the virus responsible for the deaths of millions of wild birds and domestic chickens worldwide during the last two years. HPAI kills 90 to 100 percent of domestic poultry it infects, often within 48 hours, though less is known about the mortality rates for wild birds. Corneal edema, Lamb told him, was indeed on the list of symptoms.

Enlarge (credit: Daniel Acker/Bloomberg via Getty Images )

This week, Argentina and Uruguay declared national health emergencies following outbreaks of highly pathogenic avian influenza H5N1, the fast-moving virus that destroys poultry flocks and wild birds and for decades has been feared as a possible spark for a pandemic among people. That makes 10 South American countries that have recently marked their first-ever encounter with the virus, including Peru—where more than 50,000 wild birds died last fall, and more than 600 sea lions in January. Combine the sea-lion infections with the revelation that H5N1 flu invaded a mink farm in Spain in October, and health authorities must now confront the possibility that the unpredictable virus may have adapted to threaten other species.

To be clear, this does not yet include people. Although past decades have witnessed bird flu outbreaks that spread to humans, only two cases have been identified in the past 12 months: a Colorado adult last May, and a 9-year-old girl in Ecuador in January. (Neither died.) And there’s no evidence yet that the virus has been able to jump from newly infected mammals to people. But the fact that it was transmitted from birds to mammals, and then spread among them, indicates a disquieting trend.