The U.S. Department of Agriculture is requiring dairy producers to test cows producing milk for highly pathogenic avian influenza (HPAI H5N1) infection before shipping the animals to other states after the virus was found in pasteurized milk samples collected by the Food Department. .
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The U.S. Department of Agriculture is requiring dairy producers to test cows producing milk for highly pathogenic avian influenza (HPAI H5N1) infection before shipping the animals to other states after the virus was found in pasteurized milk samples collected by the Food Department. .
Justin Sullivan/Getty Images
According to official statistics, there has been only one documented case of avian influenza being transmitted from cattle to humans during the current outbreak in the United States.
But epidemiologist Gregory Gray suspects the true number is higher, based on what he’s heard from veterinarians, farmers and workers as the virus attacks cattle herds in his state.
“We know that while H5N1 was ravaging dairy farms, some workers were seeking medical care for influenza-like illness and conjunctivitis,” said Gray, an infectious disease epidemiologist at the University of Texas Medical Branch at Galveston.
“I don’t have a way to measure that, but biologically it seems reasonable that they are also infected with the virus,” he said.
Gray has spent decades studying respiratory infections in people who work with animals, including dairy cows. He noted that “clusters of influenza-like illness and conjunctivitis” have been documented in previous bird flu outbreaks, and that these strains of bird flu are lethal to poultry, as is the case with this case.
Fortunately, genetic sequencing of the virus does not show that it has evolved to spread easily among humans.
However, epidemiologists say it is crucial to track any possible cases. They worry that some human infections may fly under the radar, especially if they are mild and short-lived, as was seen among Texas dairy workers who contracted the virus.
“I think based on how many documented cases there are in dairy cows, there could be some pretty large human exposure happening,” said Dr. Andrew Bowman, associate professor of veterinary preventive medicine at The Ohio State University. “We really don’t know.”
Limited testing raises concerns
Thirty-six cattle herds in nine states were affected. Federal health officials said at a Wednesday briefing that local and state health departments have tested about 25 people for the virus and are monitoring more than 100 people for symptoms.
Dr. Demit Daskalkakis of the Centers for Disease Control and Prevention said the individuals were “amongst the detected cattle tracks,” but he did not provide details of their actual locations.
“The threshold for individuals to get tested is very low,” he added.
The lack of testing early in the outbreak was not necessarily surprising. In places like Texas and Kansas, veterinarians didn’t consider bird flu when the disease first emerged in early March, and it took time to identify the virus as the culprit.
But to Jessica Leibler, an environmental epidemiologist at the Boston University School of Public Health, the total number of tests in humans so far appears to be low.
“If the idea is to try to identify where these facilities are causing spillover effects to humans, then you want to try to test as many workers as possible,” said Leibler, who studies novel zoonotic influenza and livestock industry risks. “.
Gray also noted that the virus may be much more widespread in cattle than reported cases suggest, and “transmission to humans may be much more likely than we knew or knew at the time.” “
The federal government quickly assessed the safety of the dairy supply. On Wednesday, the U.S. Food and Drug Administration released findings showing the absence of the infectious virus in about 200 dairy samples collected from across the country. Preliminary results for ground meat are also reassuring.
However, Leibler said there are still “serious gaps” in public health officials’ ability to detect bird flu among people who work with dairy cows, a task made more difficult by the fact that some cases may be asymptomatic. “Worker exposure to this virus is really widespread.”
Complicating matters further, the true scale of the cattle outbreak remains unclear, although new federal testing requirements for cattle moved between states may help fill that gap.
“Some dairy herds appear to have clinically normal animals but may be infected and [that] It’s really hard to know where to conduct surveillance,” Bowman said.
Call for aggressive measures to track possible human-caused cases
According to modeling done by the CDC, health care systems could see an alarming increase in human cases of avian influenza.
Federal health officials monitor flu activity in emergency rooms and hospitals. Hundreds of clinical laboratories that perform the tests are responsible for reporting the results. In early April, the CDC issued a health alert to clinicians, advising them to be on the lookout for anyone who has worked with livestock and has flu-like symptoms or conjunctivitis.
But even these safeguards may not be enough to prevent an outbreak.
“I’m concerned that if we wait until there’s a surge in these systems, maybe we’ll have seen broader community spread,” said Dr. Mary-Margaret Fair, deputy state epidemiologist for the Tennessee Department of Health. Instead, she Said active testing should be done.
Phil noted that there are anecdotal reports of farmworkers with mild illness working on cattle in some areas where the virus is circulating, and “there is not enough knowledge about the testing that is or is not happening in these populations to understand what may be happening.” Condition.
To stay ahead of the virus, Leibler said, not only workers need to be screened, but their families and others in the community, too, in case the virus does evolve to spread easily between humans.
Dr. Rodney Young said doctors in the Texas Panhandle have been on alert for any cases of the flu, especially those around livestock, but so far there have been no signs of anything unusual.
“We just haven’t seen people who fit that description suddenly being tested more,” said Young, regional director of the Department of Family and Community Medicine at the Texas Tech University Health Science Center Amarillo College of Medicine..
Get dairy farm support
Gray said it’s difficult to detect and measure illness in these rural workers for a number of reasons — their remote location, reluctance to seek health care, lack of health insurance, concerns about immigration status and farmers’ reluctance to “wave the flag” to indicate the presence of infection. .
He said the farms he works with have made protecting workers and containing the spread of the virus a “top priority” but now they bear all the risks of going public.
Dr. Fred Gingrich said this is a major obstacle to closer collaboration between federal health officials and the industry during the current crisis.
Currently, dairy farmers are not compensated for reporting infections in their herds, while poultry farmers are compensated for losses caused by culling birds when cases are discovered, said Gingrich, executive director of the American Dairymen’s Association.
“So what’s their motivation for reporting it?” he said. “It’s the same virus. It just doesn’t kill our cows.”
Gray has successfully begun collecting human and cattle samples from several dairy farms that have recently dealt with the virus. This is part of a study he initiated before the H5N1 outbreak to address concerns about the spread of SARS-CoV-2 to farms.
They will be looking for evidence of exposure to novel influenza, including avian influenza – something he is able to do because of his background in the field and his assurance that the farm will remain anonymous in the published work.
His biggest concern is that the outbreak could break out on another type of farm.
“We know when it hits poultry farms because the birds will die, but the pigs may or may not show severe disease,” he said. “The virus can be transmissible, replicate itself a lot, and has the potential to be transmitted to these workers.”
