As H5N1 spreads among cows, experts warn against drinking raw milk

SScientists who know about the types of pathogens — including E. coli and Salmonella — that can be transmitted through raw milk generally think that drinking unpasteurized milk is a bad idea. But at this point, they think, the danger associated with raw milk may have risen to a whole new level.

“If I were in charge, I would ban the sale of raw milk for the time being,” says Thijs Kuiken, a pathologist in the viroscience department of the Erasmus Medical Center in Rotterdam, Netherlands, who has researched H5N1 and the damage will last about twenty year.

The H5N1 bird flu has been circulating among dairy cow herds in several parts of the country for months. Testing of milk from infected cows shows the virus is present in concentrations that have surprised scientists. They worry that if a raw milk consumer accidentally drank milk from infected cows, the results could be bad – possibly very bad.

“I definitely wouldn’t go near raw milk in terms of consuming it,” says Richard Webby, a flu virologist at St. Jude Children’s Research Hospital in Memphis, Tenn., whose labs have been involved in tests to see if there is evidence that H5N1 RNA can be found in commercially purchased milk – it can – and whether live virus can be grown from pasteurized milk containing H5N1 RNA. So far, it seems the answer to that question is no.

While the Food and Drug Administration prohibits the sale and distribution of raw milk between states, the rules for its use in an individual state are set by the state legislature. Some ban the sale of raw milk for human consumption; others allow it under different circumstances. (Here you will find an overview per state.)

Kuiken said his concern about the risk posed by infected raw milk is not so much that the practice could somehow help the virus mutate in a way that would allow it to spread easily to and among people — with other words, could cause a pandemic. But he believes people who drink raw milk from a cow infected with H5N1 are likely to become seriously ill. Reports of the amount of virus present in infected udders are higher than anything he has seen in studies in which he experimentally infected animals with H5N1 to map the disease the virus caused, Kuiken said.

Jürgen Richt, a veterinarian and director of the Center of Excellence for Emerging and Zoonotic Animal Diseases at Kansas State University’s College of Veterinary Medicine, spoke with disbelief in his voice about the amount of dead viruses or virus particles found in commercial milk. who tested positive for the virus.

“By [results] I saw that I wouldn’t want to drink raw milk,” Richt said. “And I wouldn’t feed it to my cats, nor to my dogs, nor to my calves when I’m on a farm.”

The FDA urges consumers not to drink raw milk or eat raw milk cheeses. That’s a position the agency has long held because of the other health risks these products pose, but it’s not has re-emphasized this in the current context.

It also recommended that the dairy industry “not produce or sell raw milk or raw milk products, including raw milk cheese, made with milk from cows showing symptoms of disease, including cows infected with bird flu viruses or exposed to cows infected with bird flu viruses . .”

Kuiken said he is less concerned about raw milk cheeses because he says the various processes involved in cheese making “are not conducive to the survival of infectious viruses.” However, he did suggest that raw-milk cheesemakers could be at risk if they accidentally used milk laced with the H5N1 virus.

Whether herds of farmers who sell raw milk are infected with the virus is not publicly known. While authorities and scientists believe outbreaks are occurring in a much broader swath of the country than has been detected, the U.S. Department of Agriculture has only confirmed infections from 33 herds in nine states — Texas, Kansas, Michigan, New Mexico, Idaho, Ohio, South -Dakota, North Carolina and Colorado. No details have been given about the operations where infected animals were found.

But the USDA has admitted that some farmers are refusing to test their animals. And analysis of the genetic sequences of viruses derived from cows, combined with evidence of H5N1 RNA in commercial milk found in some U.S. markets — the FDA said Thursday that about 1 in 5 samples tested from across the country were positive for H5N1 — reinforce the argument that this has been going on for longer than recognized and likely involves many more herds than have tested positive.

Testing of commercial milk was done by polymerase chain reaction or PCR. In PCR testing, the concentration of a pathogen is estimated based on the number of cycles the test must perform to find it. The lower the cycle threshold – known as a “Ct value” – the higher the concentration. Anything with a cycle threshold of 29 or lower is considered a strong positive result. Some milk tests have shown a Ct value of less than 10, Kuiken said.

Webby, who is also director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals (based at St. Jude), said drinking raw milk contaminated with H5N1 can deliver a huge dose of virus to a person body. system – enough to cause a fatal infection in laboratory studies where small animals are experimentally infected with H5N1.

“We obviously don’t know what a lethal dose, or even an infectious dose, is in humans. But it makes absolutely no sense to me that you would want to try,” he said.

We think of flu viruses as pests that plague our upper and sometimes lower respiratory tract, causing congestion, sneezing, fever, coughing, and in some cases pneumonia. Because of their biology, the influenza A viruses that are routinely transmitted among humans — H1N1 and H3N2 — are effectively limited to infecting the cells in the respiratory tract, says Florian Krammer, an influenza virologist at the Icahn School of Medicine at Mount Sinai in New York. .

But H5N1 has more tricks up its sleeve than seasonal flu viruses; it can infect organs other than the lungs. Kuiken noted that the virus invades the liver, central nervous system and brain, among other things. He saw the latter when he experimentally infected cats in the mid-2000s. Similar results were seen when baby goats were infected with the virus on a Minnesota farm in March. Ten of the children died; Necropsies of five of them showed that they contained virus the brain and other organs.

Many of the species infected in the wild have been reported to suffer non-respiratory damage. It is believed that these animals – bears, raccoons, seals, foxes and a group of other mammals — have become infected by eating sick or dead wild birds or poultry infected with the virus.

“There are so many types that they get a brain infection and a brain disease, and not a lung disease,” Kuiken said. “In some cases the disease is missed because people expect pneumonia. If the animal is found dead, they don’t see the neurological symptoms and forget to test the brain.”

Human infection with influenza occurs when people inhale viruses shed by others into their upper respiratory tract. But the shared real estate of the upper respiratory and gastric tracts makes it impossible to rule out the possibility that ingesting food or drink that contained high levels of the viable H5N1 virus could cause an infection, scientists said.

Krammer said there are several mechanisms that could be at play. “You could get an infection from cells in the upper respiratory tract that can travel down and cause an infection of the lower respiratory tract. There could be a route where it actually goes to the olfactory bulb,” he said, and from there to the brain. “And there’s another option: It really comes through the stomach… and then you start an infection from the middle of the intestine.”

Krammer said he thought the latter option was unlikely; he thinks stomach acids would inactivate the virus. But Kuiken doesn’t believe this is necessarily true, citing his research on H5N1 in cats. Milk acts as a buffer, he said. “It’s the perfect liquid for [virus] reach the intestine in an infectious state.”

Maria Van Kerkhove, acting head of WHO’s epidemic and pandemic preparedness unit, pointed to a new outbreak involving a different virus and species – the MERS coronavirus, which spreads from camels to humans – as an example of where ingestion of virus-contaminated milk could have caused an infection of a respiratory disease. Some cases of MERS were traced to drinking raw camel milk, Van Kerkhove said, although she noted that it was generally not possible to tell whether drinking the milk or milking was the cause of the infections. (Influenza viruses and coronaviruses belong to different families.)

She acknowledged that some people take comfort in the idea that stomach acid would kill H5N1, but said it’s important to look for evidence-based answers.

The experts STAT spoke to for this story said it would also be wise for public health authorities looking for possible cases of H5N1 in humans to cast their net wide, as ingesting the virus could cause symptoms not typically associated with flu are associated. The Centers for Disease Control and Prevention has said it is monitoring emergency room data for unusual cases of flu and conjunctivitis. (There has only been one confirmed case linked to the dairy cow outbreaks so far, a farm worker in Texas who had conjunctivitis.)

“I think it is therefore important to pay attention to all kinds of strange syndromes that can occur in areas where there is more exposure and people have more exposure to dairy cattle,” says Krammer. “It could be neurological. It could actually be conjunctivitis. They may be more traditional respiratory infections. But something new can also emerge.”

“In a way we think we know H5, but the cow trick was completely new and we don’t know what the virus would do if it got into people. Maybe it does something completely unexpected. There just isn’t enough data to say anything definitive. So I think people just need to be vigilant,” he said.

Richt agreed. “Expect the unexpected. That is the situation we are dealing with here.”