Enlarge (credit: Getty | Jeffrey Greenberg )

The Food and Drug Administration reported late Thursday that about 20 percent of retail milk samples from around the country tested positive for genetic fragments of the bird flu , aka highly pathogenic avian influenza (HPAI) virus H5N1. While retail milk is still considered to be safe, the finding suggests that the spread of the virus in cows is more extensive than is currently known.

The FDA used a test called quantitative polymerase chain reaction (qPCR), which can only detect the presence of genetic fragments. In pasteurized retail milk, it is highly likely that those genetic snippets are merely remnants of virus particles destroyed during pasteurization. The FDA is currently conducting additional testing using egg inoculation tests, a gold-standard for detecting a live virus, to confirm the effectiveness of pasteurization. Meanwhile, the director of the National Institute of Allergy and Infectious Diseases, Jeanne Marrazzo, told reporters Wednesday that tests at the agency's federal labs so far did not identify live virus from any of its sampling. Additionally, several previous studies have found that pasteurization of eggs—which is done at a lower temperature than it is for milk—was effective at destroying H5N1.

While experts are largely unconcerned with the safety of commercial milk, the potential for wide, unrecognized spread of bird flu in dairy herds is alarming. To date, the US Department of Agriculture has only confirmed infections in 33 herds in eight states . The FDA acknowledged that of its positive samples, "a greater proportion of positive results [are] coming from milk in areas with infected herds." But with tens of thousands of dairy herds in the US, the finding suggests that infections are being missed. It does not necessarily suggest that 20 percent of all cows are affected, since milk is pooled for commercial distribution. But 33 herds alone are unlikely to explain the high prevalence.

Enlarge / Cows being milked (credit: Getty | Edwin Remsberg )

The Food and Drug Administration on Tuesday announced that genetic fragments from the highly-pathogenic avian influenza virus H5N1 have been detected in the pasteurized, commercial milk supply. However, the testing completed so far—using quantitative polymerase chain reaction (qPCR)—only detects the presence of viral genetic material and cannot tell whether the genetic material is from live and infectious viral particles or merely remnants of dead ones killed by the pasteurization process.

Testing is now ongoing to see if viable, infectious H5N1 can be identified in milk samples.

So far, the FDA still believes that the milk supply is safe. "To date, we have seen nothing that would change our assessment that the commercial milk supply is safe," the agency said in a lengthy explanation of the finding and ongoing testing .

Enlarge / Greylag geese sit on a field and rest while a cow passes by in the background. (credit: Getty | Daniel Bockwoldt )

Researchers around the world are growing more uneasy with the spread of highly pathogenic avian influenza (H5N1) in US dairy cows as the virus continues to make its way into new herds and states. Several experts say the US is not sharing enough information from the federal investigation into the unexpected and growing outbreak, including genetic information from isolated viruses.

To date, the US Department of Agriculture has tallied 32 affected herds in eight states : Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio, South Dakota, and Texas. In some cases, the movement of cattle between herds can explain the spread of the virus. But the USDA has not publicly clarified if all the herds are linked in a single outbreak chain or if there is evidence that the virus has spilled over to cows multiple times. Early infections in Texas were linked to dead wild birds (pigeons, blackbirds, and grackles) found on dairy farms. But the USDA reportedly indicated to Stat News that the infections do not appear to be all linked to the Texas cases .

Spread of the virus via cattle movements indicates that there is cow-to-cow transmission occurring, the USDA said. But it's unclear how the virus is spreading between cows. Given that even the most symptomatic cows show few respiratory symptoms, the USDA speculates that the most likely way it is spreading is via contaminated milking equipment.

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

The ongoing bird flu outbreak in the US is now the longest and deadliest on record. More than 57 million birds have been killed by the virus or culled since a year ago, and the deadly disruption has helped propel skyrocketing egg prices and a spike in egg smuggling.

Since highly pathogenic avian influenza (HPAI) A(H5N1) was first detected in US birds in January 2022, the price of a carton of a dozen eggs has shot up from an average of about $1.79 in December 2021 to $4.25 in December 2022, a 137 percent increase, according to data from the US Bureau of Labor Statistics . Although inflation and supply chain issues partly explain the rise, eggs saw the largest percentage increase of any specific food, according to the consumer price index .

And the steep pricing is leading some at the US-Mexico border to try to smuggle in illegal cartons, which is prohibited. A US Customs and Border Protection spokesperson told NPR this week that people in El Paso, Texas, are buying eggs in Juárez, Mexico, because they are " significantly less expensive ." Meanwhile, a customs official in San Diego tweeted a reminder amid a rise in egg interceptions that failure to declare such agriculture items at a port of entry can result in penalties up to $10,000 .