The outbreak of H5N1 avian influenza among U.S. dairy cows, first reported on March 25, has now spread to at least 33 herds in eight states. Genetic evidence of the virus recently turned up in commercially available milk. Federal authorities say the milk supply is safe, but this latest development raises troubling questions about how widespread the outbreak really is.
So far there is only one confirmed human case. Rick Bright, an expert on the H5N1 virus who served on President Joe Biden’s coronavirus advisory board, told me this is the crucial moment. “There’s a fine line between one person and 10 people with H5N1,” he said. “By the time we’ve detected 10, it’s probably too late” to contain.
That’s when I told him what I’d heard from Sid Miller, the Texas commissioner for agriculture. He said he strongly suspected that the outbreak dated back to at least February. The commissioner speculated that back then, as much as 40% of the herds in the Texas panhandle may have been infected.
Bright fell silent, then asked a very reasonable question: “Doesn’t anyone keep tabs on this?”
The H5N1 outbreak, already a devastating crisis for cattle farmers and their herds, has the potential to turn into an enormous tragedy for the rest of us. But having spent the past two weeks trying to get answers from our nation’s public health authorities, I’m shocked by how little they seem to know about what’s actually going on and how little of what they do know is being shared in a timely manner.
How bird flu spreads
How exactly is the infection transmitted between herds? The U.S. Department of Agriculture, the Food and Drug Administration and the Centers for Disease Control and Prevention all say they are working to figure it out.
According to many public health officials, the virus load in the infected cows’ milk is especially high, raising the possibility that the disease is being spread through milking machines or from aerosolized spray when the milking room floors are power washed. Another possible route is the cows’ feed, owing to the fairly revolting fact that the U.S. allows farmers to feed leftover poultry bedding material — feathers, excrement, spilled seeds — to dairy and beef cattle as a cheap source of additional protein.
Alarmingly, the USDA told me that they have evidence that the virus has also spread from dairy farms back to poultry farms “through an unknown route.” Well, one thing that travels back and forth between cattle farms and chicken farms is human beings. They can also travel from cattle farms to pig farms, and pigs are the doomsday animals for human influenza pandemics.
The USDA also told me it doesn’t know how many farmers have tested their cattle and doesn’t know how many of those tests came up positive; whatever testing is being done takes place at the state level or in private labs. Recently the agency made it mandatory to report all positive results, a long overdue step that is still — without the negative results alongside them — insufficient to give us a full picture. Also, the USDA made testing mandatory for dairy cattle that are being moved from one state to another. It says mandatory testing of other herds wouldn’t be “practical, feasible or necessarily informative” because of “several reasons, ranging from laboratory capacity to testing turnaround times.” The furthest the agency will go is to recommend voluntary testing for cattle that show symptoms of the illness — which not all that are infected do. Bright compares this to the Trump administration’s approach to COVID-19: If you don’t test, it doesn’t exist.
As for the FDA, it tells me it hasn’t completed specific tests to confirm that pasteurization would make milk from infected cows safe, though the agency considers it “very likely” based on extensive testing for other pathogens. (It is not yet clear whether the elements of the H5N1 virus that recently turned up in milk had been fully neutralized.) That testing should have been completed by now. In any case, unpasteurized milk remains legal in many states.
Making matters worse, the USDA failed to share the genomes from infected animals in a timely manner, and then did so in an unwieldy format and without any geographic information, causing scientists to tear their hair out in frustration.
Too few tested
All this makes catching potential human cases so urgent. Bright says that given a situation like this, and the fact that undocumented farmworkers may not have access to health care, the government should be using every sophisticated surveillance technique, including wastewater testing, and reporting the results publicly. That is not happening. The CDC says it is monitoring data from emergency rooms for any signs of an outbreak. By the time enough people are sick enough to be noticed in emergency rooms, it is almost certainly too late to prevent one.
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So far, the agency told me, it is aware of only 23 people who have been tested. That tiny number is deeply troubling. (Others may be getting tested through private providers, but if negative, the results do not have to be reported.)
On the ground, people are doing the best they can. Adeline Hambley, a public health officer in Ottawa, Michigan, told me of a farm whose herd had tested positive. The farm owner voluntarily handed over the workers’ cellphone numbers, and the workers got texts asking them to report all potential symptoms. Lynn Sutfin, a public information officer in the Michigan Department of Health and Human Services, told me that response rates to those texts and other forms of outreach can be as high as 90%. That’s heartening, but it’s too much to expect that a poor farmworker — afraid of stigma, legal troubles and economic loss — will always report even mild symptoms and stay home from work as instructed.
It’s entirely possible that we’ll get lucky with H5N1 and it will never manage to spread among humans. Spillovers from animals to humans are common, yet pandemics are rare because they require a chain of unlucky events to happen one after the other. But pandemics are a numbers game, and a widespread animal outbreak like this raises the risks. When dangerous novel pathogens emerge among humans, there is only a small window of time in which to stop them before they spiral out of control. Neither our animal farming practices nor our public health tools seem up to the task.
Zeynep Tufekci is a New York Times columnist.
