Less than a week after California health officers confirmed a finding of bird flu virus in store-bought raw milk, state agriculture officials descended on Mark McAfee’s Raw Farm dairy “like never before” Wednesday and began collecting samples from the farm’s two herds, creamery, bulk milk tanks and trucks, according to the owner.

The visit follows a recall of Raw Farm products, and also comes amid a growing series of H5N1 bird flu outbreaks in state dairy farms. Raw Farm maintains 1,800 head of cattle spread over two herds — one in Fresno, the other outside of Hanford, according to McAfee. The company also owns a Fowler-based creamery.

“I think they are on full attack mode,” he said, describing the search as thorough. In addition to milk, Raw Farm produces cheese and kefir.

As California Department of Food and Agriculture officials collected samples and conducted tests at the dairy Wednesday, some health experts raised questions and concerns about the recent positive test results.

Last week, public health officials in Santa Clara County detected bird flu virus in a store-bought sample of McAfee’s raw milk. Two days later, the California Department of Public Health confirmed the finding.

But when state agriculture officials tested cows at McAfee’s dairy farm on Monday, they failed to detect the virus.

The fact that none of the animals are known to be infected with the virus has puzzled and concerned public health experts. Generally, once the virus appears on a farm, it spreads and does not just disappear.

“The fact that all the supplemental testing is negative really bothers me,” said John Korslund, a retired U.S. Department of Agriculture veterinarian epidemiologist, in an email.

Officials from the CDFA could not be reached for comment Wednesday, but infectious disease experts told The Times that officials were likely reviewing testing procedures, as well as the actual origin of the sampled milk.

According to testing records, the initial sample of store-bought raw milk carried high levels of the virus, and was found to have a polymerase chain reaction cycle threshold — or Ct — of roughly 25.

“A herd should not be immediately negative after a reading of 25 if it is truly milk from the same herd, IMO,” Korslund wrote in an email.

Richard Webby, director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds, and a researcher in the department of Infectious Diseases at St. Jude’s Children’s Research Hospital in Memphis, Tenn., agreed.

“OK, that’s not a weak positive … and definitely not on the borderline where some tests would be positive and others negative,” he said after reviewing the test records.

Webby, Korslund and other experts say the test that was used only looks for the H5 part of the H5N1 virus, and it can’t determine if the virus is inactive, or alive. A second test — one called a virus isolation test — needs to be done to confirm the sample is H5N1 and that it is active.

State and federal health officials say the H5N1 bird flu virus poses a low risk to the public. However, they have urged people not to drink raw, unpasteurized milk. There has been no reported outbreak in consumers associated with the bird flu in contaminated raw milk.

The milk was bottled on Nov. 9. Raw Farm LLC has recalled all products associated with the positive sample. McAfee estimates the recall involved roughly 2,000 gallons of half- and quarter-gallon “cream top” whole milk products.

Since the beginning of the outbreak, 461 herds have been infected in California — including herds in Fresno and Kings County, where McAfee’s herds are located.

Early in the H5N1 dairy outbreak, federal health officials tested pasteurized milk samples and found virus in 20% of the samples collected from retail shelves. However, when further testing was conducted — virus isolation — they were able to show it was inactivated virus that had been denatured by heat.

So, why then would a raw milk sample test highly for virus and a dairy herd not test positive?

Korslund acknowledged that testing and sampling can sometimes be compromised, but he was not inclined to doubt the tests in this instance. He said the Ct value — and the lack of subsequent positive tests — suggests a “product integrity issue rather than a herd infection.”

“What if somewhere in the bottling process, pasteurized shelf milk was spiked into the raw milk to meet inadequate supply demands? In such a scenario, we don’t have a testing issue; rather it’s a product integrity issue that normally would be undetectable,” he said.

This is why virus isolation testing is critical, Korslund said. It would help determine whether the virus in the sample collected was alive or not.

A spokesman for the state’s health department said testing on the sample was complete. He did not say whether viral isolation had been completed, but noted the positive result has been confirmed by state and now federal laboratories.

McAfee said he does not think the virus is present in his herd. The tests that the state’s agriculture department have been regularly conducting — twice a week — on his bulk milk have been negative. In addition, he noted, a test taken on Monday also showed no virus.

In addition, he said, he monitors each cow at his farms with a high-tech device — made by the Austrian company smaXtec — which sits in a cow’s udder and sends real-time information about the animal’s body temperature, milk acidity, etc.

He said there are no indications that virus is moving through his herd based on that data.

He also said all his equipment — from his trucks, to his bulk tanks and bottling plant — are closed to outside farms and milk; they are used only by Raw Farm, LLC.

He said he’s worried state officials are determined “to find something.”

California health officials announced Wednesday that another batch of raw milk from Fresno-based Raw Farm has tested positive for bird flu virus, as dairy farms throughout the state continue to struggle with a widening number of outbreaks.

For the second time in roughly the span of a week, Santa Clara County Department of Public Health officials tested store-bought raw milk and found evidence of the virus. The sample was collected and tested on Tuesday.

Raw Farm is voluntarily recalling a batch of “cream top” whole milk half-gallon-size products, lot No. 20231119, expiration date Dec. 7.

According to Mark McAfee, the owner of Raw Farm, the state’s Department of Food and Agriculture has requested that he “hold delivery of further products” until Friday.

On Wednesday, state agriculture officials visited his farms in Fresno and Hanford, as well as his creamery in Fowler, and tested finished and unfinished products, as well as his trucks, bulk tanks and bottling facility.

He said the investigation was carried out with a thoroughness “like never before.”

There have been no reported illnesses associated with either this second recall or the first. The first recall also involved Raw Farm and was limited to a batch that was bottled on Nov. 9.

State and federal health officials say the H5N1 bird flu virus poses a low risk to the public. However, they have urged people not to drink raw, unpasteurized milk.

In addition, every waste site tested in California by WastewaterScan — an infectious-disease monitoring network led by researchers at Stanford and Emory University, with lab testing partner Verily, Alphabet Inc.’s life sciences organization — has tested positive for bird flu in the last two weeks.

The Los Angeles County Department of Public Health issued a statement late Wednesday expanding the list of stores that may have sold bird-flu-contaminated raw milk.

They include:

• Back Door Bakery, 8349 Foothill Blvd., Sunland, CA 91040
• Bristol Farms, 7880 Sunset Blvd., Los Angeles, CA 90046
• Eataly, 10250 Santa Monica Blvd., Los Angeles, CA 90067
• Erewhon Market, 475 S. Lake Ave., Pasadena, CA 91101
• Erewhon Market, 26767 Agoura Road, Calabasas, CA 91302
• Erewhon Market, 4121 Santa Monica Blvd., Los Angeles, CA 90029
• Erewhon Market, 7660 Beverly Blvd., Los Angeles, CA 90036
• Lassen’s Natural Foods, 1631 W. Sunset Blvd., Los Angeles, CA 90026
• Lassen’s Natural Foods, 2080 Hillhurst Ave., Los Angeles, CA 90027
• Lassen’s Natural Foods, 710 S. La Brea Ave., Los Angeles, CA 90036
• Lazy Acres, 1841 N. Western Ave., Los Angeles, CA 90027
• Lazy Acres, 2510 Pacific Coast Highway, Hermosa Beach, CA 90254
• Mothers Market & Kitchen, 6677 W. Santa Monica Blvd., Los Angeles, CA 90038
• Mothers Market & Kitchen, 2475 Cherry Ave., Signal Hill, CA 90755
• Sprouts Farmers Market, 1302 S. La Brea Ave., Los Angeles CA 90019
• Sprouts Farmers Market, 1751 Westwood Blvd., Los Angeles CA 90024
• Sprouts Farmers Market, 8985 Venice Blvd., Los Angeles CA 90034
• Sprouts Farmers Market, 915 N. La Brea Ave., Los Angeles, CA 90038
• Sprouts Farmers Market, 2245 Yosemite Drive, Eagle Rock, 90041
• Sprouts Farmers Market, 7925 Atlantic Ave., Cudahy CA, 90201
• Sprouts Farmers Market, 5660 Sepulveda Blvd., Culver City CA, 90230
• Sprouts Farmers Market, 12060 Lakewood Blvd., Downey, CA 90242
• Sprouts Farmers Market, 14411 Hawthorne Blvd., Lawndale, CA 90260
• Sprouts Farmers Market, 1515 Hawthorne Blvd., Redondo Beach, CA 90278
• Sprouts Farmers Market, 4230 Pacific Coast Highway, Torrance CA, 90505
• Sprouts Farmers Market, 15801 Whittier Blvd., Whittier, CA 90603
• Sprouts Farmers Market, 11522 Alondra Blvd., Norwalk, CA 90650
• Sprouts Farmers Market, 11900 South St., Cerritos, CA 90703
• Sprouts Farmers Market, 4253 Woodruff Ave., Lakewood, CA 90713
• Sprouts Farmers Market, 820 N. Western Ave., San Pedro, CA 90732
• Sprouts Farmers Market, 4600 E. Pacific Coast Highway, Long Beach, CA 90804
• Sprouts Farmers Market, 920 Foothill Blvd., La Cañada Flintridge, CA 91011
• Sprouts Farmers Market, 400 W. Huntington Drive, Monrovia, CA 91016
• Sprouts Farmers Market, 39 N. Rosemead Blvd., Pasadena, CA 91107
• Sprouts Farmers Market, 6607 Fallbrook Ave., West Hills, CA 91307
• Sprouts Farmers Market, 10821 N. Zelzah Ave., Granada Hills, CA 91344
• Sprouts Farmers Market, 24285 Magic Mountain Pkwy., Valencia, CA 91355
• Sprouts Farmers Market, 21821 Ventura Blvd., Woodland Hills, CA 91364
• Sprouts Farmers Market, 1011 N. San Fernando Blvd., Burbank, CA 91504
• Sprouts Farmers Market, 11315 Ventura Blvd., Studio City, CA 91604
• Sprouts Farmers Market, 835 W. Foothill Blvd., Claremont, CA 91711
• Sprouts Farmers Market, 655 S Grand Ave., Glendora, CA 91740
• Sprouts Farmers Market, 1375 Foothill Blvd., La Verne, CA 91750
• Sprouts Farmers Market, 239 S. Diamond Bar Blvd., Diamond Bar, CA 91765
• Sprouts Farmers Market, 2630 E. Workman Ave., West Covina, CA 91791
• Sprouts Farmers Market, 150 E Main St., Alhambra, CA 91801
• Vitamin City LB, 6247 E. Spring St., Long Beach, CA 90808
• Vitamin City, 642 W. Arrow Highway, San Dimas, CA 91773
• Whole Wheatery, 44264 10th W., Lancaster, CA 93534

Your heart is racing, your arms are tingling and your breathing is shallow. You’re having an anxiety attack. And you’re in a public place, to boot. A crowded restaurant, say, or at the office. Not a space where you can comfortably lay on the ground and do some deep breathing exercises to calm yourself.

What if there were a pill that would instead induce that kind of calm breathing for you? That scenario might be possible after a new scientific breakthrough.

Neuroscientists at the Salk Institute for Biological Studies in La Jolla have identified a brain pathway that instantly deflates anxiety. The new study, which published earlier this week in the scientific journal Nature Neuroscience, lays out how the aforementioned brain circuit regulates voluntary breathing — meaning conscious breathing as opposed to automatic breathing that happens without your having to think about it — allowing us to slow our breath and calm our mind.

The discovery opens up the potential for the creation of new drugs that would mimic the relaxed state common during breath work, meditation or yoga. Sung Han, senior author of the study, says he’d like to one day see a “yoga pill,” as he calls it, on the market to ease anxiety. It would likely be useful for the more than 40 million adults in the U.S, who, according to the National Alliance on Mental Illness, suffer from an anxiety disorder.

Han says the new discovery is a real scientific breakthrough.

“As a scientist, finding something never known before is always exciting,” he told the Los Angeles Times. “This top-down breathing circuit has been a longstanding question in the neuroscience field. It’s exciting to find the neural mechanism to explain how the slowing down of breathing can control negative emotions, like anxiety and fear.”

We’ve long known that we can control our breathing patterns to alter our state of mind — when we get stressed, we might take a deep, slow breath to feel calmer. But scientists didn’t understand how that worked — which parts of the brain were actually slowing our breath and why that activity makes us calmer. Now they know that there is a group of cells in the cortex, the higher part of the brain responsible for more conscious, complex thought, that send messages to the brain stem, which in turn sends information to the lungs. That’s the aforementioned “circuit.”

The discovery validates soothing behavioral practices such as yoga, mindfulness and even “box breathing” — the latter a technique that involves repeatedly breathing in, then holding your breath, for four-second counts in order to relieve stress — because it grounds these behavioral practices in science.

But the practical applications is what makes the Salk discovery so important, Han says.

“It can, potentially, create a whole new class of drugs that can more specifically target anxiety disorder,” he says.

These would differ from common anti-anxiety medications by more specifically targeting areas of the brain. Common anti-anxiety drugs like Xanax and Lexapro target multiple areas of the brain that control multiple brain processes and behaviors. It’s why these drugs don’t work for everyone in the same way and may create unwanted side effects. More precisely targeting an individual brain circuit makes a medication more effective and reduces potential side effects. And, in extreme cases, such a pill might be more efficient for targeting anxiety than doing breathing exercises.

“If you’re in panic, breathing techniques alone may not be sufficient to suppress anxiety,” Han says.

Han’s team is now trying to find the opposite circuit — a fast breathing circuit — that increases anxiety.

“To target the slow breathing circuit, we need to understand the opposite circuit, so we can avoid targeting it,” Han says. “To relieve the anxiety.”

While Han hopes his findings will lead to a “yoga pill,” that’s likely a long ways off. The research, and ensuing clinical trials, could take as much as 10 years, he says. And nothing is for certain.

“I cannot say that this discovery is directly connected to the discovery of the new medication,” Han says. “But I can say it’s a stepping stone. We now know the pathway. That’s exciting. That is the first step.”