The U.S. Food and Drug Administration said Tuesday that samples of pasteurized milk had tested positive for remnants of the bird flu virus that has infected dairy cows.
The agency stressed that the material is inactivated and that the findings “do not represent actual virus that may be a risk to consumers.” Officials added that they're continuing to study the issue.
“To date, we have seen nothing that would change our assessment that the commercial milk supply is safe,” the FDA said in a statement.
The announcement comes nearly a month after an avian influenza virus that has sickened millions of wild and commercial birds in recent years was detected in dairy cows in at least eight states. The Agriculture Department says 33 herds have been affected to date.
FDA officials didn't indicate how many samples they tested or where they were obtained. The agency has been evaluating milk during processing and from grocery stores, officials said. Results of additional tests are expected in “the next few days to weeks.”
The PCR lab test the FDA used would have detected viral genetic material even after live virus was killed by pasteurization, or heat treatment, said Lee-Ann Jaykus, an emeritus food microbiologist and virologist at North Carolina State University
“There is no evidence to date that this is infectious virus and the FDA is following up on that,” Jaykus said.
Officials with the FDA and the USDA had previously said milk from affected cattle did not enter the commercial supply. Milk from sick animals is supposed to be diverted and destroyed. Federal regulations require milk that enters interstate commerce to be pasteurized.
Because the detection of the bird flu virus known as Type A H5N1 in dairy cattle is new and the situation is evolving, no studies on the effects of pasteurization on the virus have been completed, FDA officials said. But past research shows that pasteurization is “very likely” to inactivate heat-sensitive viruses like H5N1, the agency added.
Matt Herrick, a spokesman for the International Dairy Foods Association, said that time and temperature regulations for pasteurization ensure that the commercial U.S. milk supply is safe. Remnants of the virus “have zero impact on human health,” he wrote in an email.
Scientists confirmed the H5N1 virus in dairy cows in March after weeks of reports that cows in Texas were suffering from a mysterious malady. The cows were lethargic and saw a dramatic reduction in milk production. Although the H5N1 virus is lethal to commercial poultry, most infected cattle seem to recover within two weeks, experts said.
To date, two people in U.S. have been infected with bird flu. A Texas dairy worker who was in close contact with an infected cow recently developed a mild eye infection and has recovered. In 2022, a prison inmate in a work program caught it while killing infected birds at a Colorado poultry farm. His only symptom was fatigue, and he recovered.
Following continued concerns about bird flu, the Food and Drug Administration (FDA) confirmed via testing that the commercial milk supply in the United States is safe. The new tests, which were done on milk samples across the country, confirmed that pasteurization effectively kills the bird flu virus, as no live virus was found in the samples. Additionally, tests on powdered infant formula and milk products for toddlers also came back negative for any viral fragments.
The FDA is also further testing retail samples from its study of 297 samples of dairy products from 38 states. “All samples with a PCR positive result are going through egg inoculation tests, a gold-standard for determining if infectious virus is present,” the FDA said in a statement.
Traces of bird flu have been found in 1 in 5 samples of pasteurized milk, sparking worry that the virus — also known as avian influenza — could be transmitted to humans. So far, only one person in the U.S. has caught bird flu, the second ever case in the nation. The Centers for Disease Control and Prevention (CDC) has asked states to prepare for more bird flu cases by gearing up to test at-risk people for the virus, and insists that the risk to the general public remains low, Reuters reports.
The one infected person is a dairy worker who contracted bird flu in Texas, where the virus has been spreading among cattle, as well as in Idaho, Kansas, Michigan, New Mexico, North Carolina, Ohio and South Dakota. Bird flu hasn’t spread to any other people so far, but it has been detected in wild birds, including several geese, in New York City parks and green spaces, according to a new study, and there are renewed fears about other mammals being infected.
How concerned should you be about bird flu, and what might this mean for the food supply? Here’s what you need to know.
Bird flu — clinically known as influenza A (H5N1) — is a variation of flu virus that spreads primarily among birds and poultry and can be highly contagious and even fatal among birds, according to the CDC. Occasionally, the virus will jump to other animals if they eat infected birds or drink water contaminated by the feces of infected birds, the CDC says. That has become more common in recent years. Viruses are constantly mutating, and the more they spread, the more they mutate. A recent family of variants may be particularly adept at infecting other animals, including cattle, according to the World Health Organization.
It’s rare for the virus to infect humans, and when it does happen, it’s usually confined to one person who was in close contact with an infected animal and doesn’t spread to others. Bird flu may cause mild to severe sickness in humans, and it has the potential to cause pneumonia and severe, sometimes fatal lung inflammation. Since 2020, there have been 26 cases in humans confirmed by the WHO, seven of which have been fatal.
❓Have people been infected?
The CDC continues to call for calm and considers the risk to the general public low, but, on Apr. 5, the agency requested that state health departments begin gearing up in case additional people are infected.
So far the U.S. Department of Agriculture (USDA) has confirmed that there are 12 infected dairy cattle herds in Texas, four in Kansas, six in each New Mexico and Michigan, two in Idaho and one each in North Carolina, Ohio and South Dakota. Cases in birds in New York City parks and green spaces have also been confirmed by Icahn School of Medicine at Mount Sinai researchers.
The infected person in Texas was diagnosed after developing conjunctivitis, or pink eye. It’s only the second-ever human case of bird flu in the U.S.; the first was a poultry farmworker who was infected in 2022 while culling infected birds and recovered after experiencing only mild fatigue. Eye inflammation is the only symptom of the person currently infected, and they’re receiving antiviral medication.
Other dairy and poultry farmworkers are the CDC's main concern now. As of April 24, the CDC had tested 23 people for bird flu, and states with outbreaks were monitoring 44 people who were exposed to the virus, according to the New York Times. The agency has asked state health officials to take steps like making sure they have bird flu tests available to confirm possible infections. It also said health officials should stay in close contact with veterinarians and agriculture department officials and asked to be notified of any "challenges" states encounter.
While farmworkers are at the greatest risk because of their close and frequent proximity to potentially infected animals, the Icahn School of Medicine study authors warned that it's not impossible for city dwellers to be exposed. "Our work highlights that the interface between animals and humans that may give rise to zoonotic infections" — germs that spread between animals and people — "or even pandemics is not limited to rural environments and commercial poultry operations but extends into the heart of our urban centers," the researchers wrote.
Read more: Bird flu is infecting more mammals. What does that mean for us?
🏥 What are the risks to humans?
For the general public, the risk remains low, the CDC says. Bird flu has never been very good at spreading from person to person, so it’s unlikely to become widespread. The virus would have to mutate in some specific, key ways to make that possible. The good news is that it hasn’t, according to preliminary testing of a sample of virus from the infected person, who has only mild symptoms.
🥛 What does it mean for our food and milk?
Testing of commercial milk — the kind sold in grocery stores — detected genetic remnants of the bird flu virus, which has infected both egg-laying chickens and dairy cows in the U.S., in about 20% of samples, according to the FDA. That doesn't necessarily mean the milk can make you sick, but regulators are now performing additional tests to determine "if infectious virus is present," the FDA said on April 25.
According to the FDA's statement, while pasteurization — a sterilization process that kills bacteria and viruses — likely inactivates the virus — meaning that it should not be able to infect someone who drinks milk — it "is not expected to remove the presence of viral particles." So far, the agency has "seen nothing that would change our assessment that the commercial milk supply is safe," officials said in the statement. The USDA echoed that sentiment, maintaining that "that there is “no concern about the safety of the commercial milk supply because products are pasteurized before entering the market.”
Still, the USDA has stepped up efforts to stop bird flu from spreading. On April 24, the agency issued a federal order telling dairy farms to test any cattle being moved across state lines for bird flu. The agency had previously told farmers to test any cattle with symptoms and throw out milk from infected cows. And other countries are concerned: Colombia is now restricting the importation of beef and beef products from U.S. states with infected herds, becoming the first country to do so on April 15, Reuters reported.
Bird flu has also been found in unpasteurized milk, but you shouldn’t consume unpasteurized milk or cheese regardless, the CDC warns, because they carry risks of infections, like listeria. The CDC also notes that the risk of being infected from eating eggs is low, and properly cooking them would kill any virus anyway.
Farms are prohibited from selling products — including milk and eggs — from sick animals, so it’s unlikely that contaminated food would wind up on grocery store shelves. The most likely impact of the bird flu outbreak in animals on the food supply is rising prices. Egg prices have shot up as chickens have been culled or died, limiting the supply of eggs. Milk prices could see increases but are stable so far.
Read more: As bird flu spreads in cows, fractured U.S. response has echoes of early COVID
💉 Are there bird flu vaccines and treatments?
Two candidate vaccines — drafts of what would become the shots — seem to be good matches for the current strain of bird flu, the Washington Post reports. The U.S. federal government has a stockpile of enough doses to vaccinate a fifth of the American population, officials told Barron's. However, the vaccines are undergoing clinical testing, so it's unclear how effective they will be. Antiviral drugs can also be used to treat bird flu, although the CDC says that some variations of bird flu first found in Asia aren’t as responsive to these treatments.
Dr. Arnold Monto, a professor emeritus of epidemiology at the University of Michigan and member of the FDA’s vaccine committee, tells Yahoo Life that the U.S.’s bird flu vaccines require adjuvants, ingredients that improve human’s immune responses. An official with the Department of Health and Human Services also told the Washington Post that components for the vaccines are being tested, and it would likely take weeks to months for them to be ready for widespread distribution. Monto adds that the vaccine would also likely be given to only those at high risk — poultry and dairy farmworkers — since there’s no evidence that bird flu spreads among humans.
🙅 How can I avoid bird flu?
Avoid close or prolonged contact with wild birds, cattle or any other animal suspected of being infected. The CDC also recommends steering clear of surfaces that may be contaminated with raw milk, animal feces, litter or anything else that might have crossed paths with an infected animal.
Cooking poultry and eggs to an internal temperature of 165˚F will kill off any virus. It's also recommended for milk drinkers to consume only pasteurized milk to prevent contracting bird flu or other viruses or bacteria from raw foods, and to avoid raw or undercooked foods sourced from animals that may be infected with bird flu.
A new report from the Food and Drug Administration (FDA) found traces of a highly pathogenic avian influenza (HPAI) in commercially sold pasteurized milk from several states.
According to the report, which was published on Thursday, 1 in 5 samples of commercially sold pasteurized milk contained viral fragments of H5N1, a virus known as “bird flu,” that researchers say typically infects birds, poultry and other animal species. The fragments in the milk were not live or infectious, NBC News reported.
The report found that a large number of the milk samples containing traces of bird flu came from areas that had cows infected by the virus.
But the agency said that commercial milk is still safe because of the pasteurization process, which kills bacteria, and because of the destruction of milk from cows infected by the virus, which are two federal and state measures taken to ensure milk safety for consumers.
“Even if [the] virus is detected in raw milk, pasteurization is generally expected to eliminate pathogens to a level that does not pose a risk to consumer health,” the FDA said.
The H5N1 bird flu is not a new virus. According to the World Health Organization, the virus was first found in humans in 1997 in Hong Kong. But researchers say that the virus has primarily infected birds on poultry farms.
Since 2022, more than 58 million domestic birds like chickens, ducks and turkeys in the United States have died from H5N1.
Scientists have also found that other mammals have been infected by the virus. In October 2022, a mink fur farm in Spain had an outbreak of the virus, indicating to researchers the potential for mammal to mammal transmission, as well as transmission to humans.
From 2003 to 2016, more than 800 people were infected with H5N1, with the mortality rate at more than 50%, according to the National Center for Biotechnology Information. There have been five confirmed human cases worldwide and one death since October 2021, BBC reported.
Experts worry about the possibility of an H5N1 pandemic among humans, warning that the lack of clear and timely updates on the outbreak by some federal agencies, including failures to provide updates on the spread of H5N1 in cows and the safety of milk supplies, is reflective of the miscommunication steps at the beginning of the COVID-19 pandemic, The Washington Post reported.
“This requires multiple agencies to coordinate and communicate internally, but most importantly externally, which doesn’t seem to be happening due to different cultures, priorities, legal responsibilities, scientific expertise, and agility,” epidemiologist Katelyn Jetelina, who has closely tracked the avian flu outbreak, told the Post. “Mix that in with the usual challenges of scientific uncertainty, complexity and, quite frankly global pressure, and you got yourself an utterly, unacceptable mess.”
The U.S. Department of Agriculture, along with the Centers for Disease Control and Prevention, FDA and state partners, are investigating the spread of the avian virus among dairy cows in several states across the country.
The FDA will continue testing milk supplies to further determine potential risks for consumers, and additional information will be released in the future.
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