Each milk sample was pasteurized, a heating process designed to kill pathogens leaving behind inactive virus particles. It is rare for humans to become infected with H5N1.
In some ways, the preliminary results are reassuring, some public health experts said. More than three-quarters of the samples were processed at New England dairy plants and none returned a definitive positive result. The only positive sample was processed in a state with an outbreak of avian flu among dairy cows.
“It’s remarkable that New England is still case-free (on dairy farms) given how widespread the H5N1 virus is, but it’s probably only a matter of time before we are exposed,” said Pardis Sabeti, the Broad Institute geneticist whose lab conducted the tests. “This is a unique moment of opportunity to ensure our farms are protected and prosperous through testing and monitoring. »
The goal of Broad’s testing was to determine whether the virus was present on New England farms, putting farm workers and those who consume locally purchased unpasteurized dairy products at risk of infection.
The results provide the first known evidence that the virus – at least in its inactive form – is now present in food products consumed in New England. They also underscore the scale and persistence of the threat and highlight the changing nature of dairy production in New England and nationally.
Last month, the FDA conducted its own tests on store-bought milk, purchasing 297 dairy products samples including milk from 38 states. It found viral fragments in 20 percent of the samples. But the agency did not reveal where the milk was purchased.. In a separate study, researchers from Ohio State and the University of Illinois purchased 150 samples in 10 states. More than a third have tested positive.
The more the virus spreads, the more likely it is to develop genetic changes that allow it to more easily infect mammals, including humans.
To find out if H5N1 was present in local supermarkets, Globe employees fanned out across Massachusetts, Rhode Island and New Hampshire earlier this week, heading to the dairy sections of Star Market, Stop & Shop, Cumberland Farms, Whole Foods, Traders Joe’s, Shaws, Target and a wide range of other stores.
They delivered the milk in coolers to Sabeti’s laboratory located in Kendall Square in Cambridge. After using specialized machines to extract any genetic material present and replicate it 1 billion times, members of her lab then added fluorescent chemical particles that made any fragment of the H5N1 virus visible to a specialized camera, explained Elyse Stachler, research scientist who led the study. genetic test. Each sample was tested twice before the technicians gave their verdict. Some underwent a third, even more rigorous test.
Many experts fear the virus is much more widespread on dairy farms across the country than currently believed. Federal regulations now require H5N1 testing for cows to be transported across state lines. But otherwise most tests remain voluntary. To date, only about 30 people have been tested for the virus nationwide by state and local authorities, federal officials said recently.
“The way they are trying to detect the virus on farms is woefully inadequate,” said Jennifer Nuzzo, professor of epidemiology and director of the Pandemic Center at the Brown University School of Public Health. “Our current testing program is dangerous. We remain concerned about the possibility that the virus will evolve to acquire the ability to infect humans more easily.
Dr. Catherine M. Brown, state epidemiologist and public health veterinarian with the Massachusetts Department of Public Health, said the discovery of viral fragments in milk did not surprise her given previous federal testing results. Since the CDC has deemed the virus to pose a low risk to human health, monitoring its spread remains a “collaborative effort” that is still conducted at the state level by the Massachusetts Department of Agricultural Resources. To date, no confirmed cases of H5N1 in cows or humans have been reported in the state.
The state’s milk remains safe. The exception, she notes, is raw milk.
“Raw milk is an everyday concern, regardless of H5N1, because it can and frequently does contain bacterial pathogens that cause serious illness and even occasional death in people,” she said.
Since its arrival in the United States at the end of 2021, carried by migratory birds, the H5N1 virus has caused the death of tens of millions of birds and developed new mutations which have already allowed it to be transmitted to mammals. In New England, numerous sea ducks, loons and gulls have littered the beaches of the North Shore in recent months, washing up at Nahant Beach, Salisbury, Newbury, Newburyport, Plum Island and Manchester-by-the-Sea.
The USDA announced in March that cows were first infected on farms in Texas and Kansas and reported shortly after that a farm worker had been infected in what is believed to be the first known case of a mammal infecting a human. (This worker, who had mild symptoms, has since recovered.)
Some experts say the low positivity rate of milk samples purchased by the Globe could result from the unique characteristics of the region’s dairy industry, which could have, at least until now, protected our farms from wide exposure to the epidemic.
“The New England dairy industry is very different from that of the Southwest, California and parts of the Midwest,” said Jim Lowe, professor of food animal medicine and associate dean of the College. in Veterinary Medicine from the University of Illinois. member of the team that tested milk samples purchased in 10 Western states.
In recent years, the domestic dairy industry has been subject to brutal cost pressures, which have catalyzed sector-wide consolidation and the proliferation of large farms. Since the early 1950s, the number of dairy farms nationwide has increased from 3 to 4 million to approximately 24,000. today, said Andrew Novakovic, an agricultural economist at Cornell University.
Many of these farms are increasingly outsourcing the care of immature female calves, shipping them to specialized farms that raise them, he said. When these cows become “spring heifers” – cows in the final weeks of gestation – they are returned to their original farms and reintroduced into their original herds as dairy cows just before giving birth. The H5N1 virus developed the mutation that allowed it to infect cows in Texas in December and is believed to have spread quietly from state to state, carried by traveling heifers, experts say.
However, the practice of transporting heifers out of state is rare in New England, due to a Yankee “can-do attitude” that disapproves of contracting out tasks. to raise young cows, said Eugene White, professor of ambulatory medicine at the Cummings School of Veterinary Medicine at Tufts.
New England has lost more than 10,000 dairy farms in the past 50 years. There are 480 dairy farms remaining in Vermont, 151 in Massachusetts, 83 in Connecticut, 129 in New Hampshire, five in Rhode Island and 290 in Maine, according to Michael de Angelis, vice president of New England Dairy, a group defense of the industry.
As a result, the region became increasingly dependent on milk. other states, New England producing far less milk than its inhabitants consume. The only region in the country with a comparable disparity between cows and people is the area around Miami, White said. This helps explain why some of the milk samples purchased at area stores were processed as far away as California, Colorado and Minnesota, according to factory codes printed on most milk containers.
Jason Laughlin of the Globe staff contributed to this report.
Adam Piore can be contacted at adam.piore@globe.com.