Protecting families from contaminated food and water
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Protecting families from contaminated food and water
Posted in Our Blog on May 24, 2025
A new study suggests that bird flu spread by wind is a serious possibility.
With more than 150 million US bird deaths since February 2022, rising egg costs, and mounting uncertainty, this theory complicates biosecurity efforts.
In birds, avian influenza (bird flu) is a death sentence.
It is highly pathogenic. Which means that just about every bird who gets it dies from their illness. To manage spread in poultry flocks, once it is discovered all birds in the flock are culled.
Many of the human cases of bird flu have been traced back to poultry farms. According to the latest bird flu situation report, 24 of the 70 human cases of bird flu were linked to poultry farms and culling operations.
In cows, bird flu is fairly asymptomatic. A decline in milk output seems to be one of the only indicators of illness.
Most (41 cases) of the human cases of bird flu have been traced back to dairy cattle. While bird flu has been identified in cow’s milk, it is unclear as to whether humans can become sick from consuming it. Some studies have found mice and monkeys, however, do become sick from consuming contaminated milk.
There have been two human cases of bird flu where another animal exposure was determined to be the source and another three where the exposure source was unknown.
While bird flu isn’t a typical infection in humans, the above-mentioned cases indicate that the possibility is still real. But how does bird flu spread in humans?
According to the Centers for Disease Control and Prevention (CDC), most cases of bird flu have occurred after “close or lengthy unprotected contact” with infected birds or places that sick birds or their saliva, mucous and feces have touched.”
Humans become infected when the virus gets into their eyes, nose, mouth, or is inhaled. Often from breathing in infected droplets or dust or touching their mouth, eyes, or nose after touching something contaminated with the virus.
In humans, bird flu symptoms range from no symptoms at all to mild illness (eye infection and upper respiratory symptoms). Though some severe cases causing pneumonia have resulted in hospitalization and death.
Person-to-person spread has not been observed in the United States.
The study centers on an outbreak among “unrelated commercial poultry farms located 8 kilometers (5 miles) apart.”
This outbreak took place in the Czech Republic in February 2024 during the country’s 2023 – 2024 season.
One cluster of illnesses was identified at a basic-biosecurity 50,000-bird farm near a lake frequented by wild ducks. Bird flu sickened and killed 5,000 fattening ducks within two days. At the time, the wild ducks were suspected as the source of the infection. The rest of the poultry were culled to prevent further spread.
Just one week later, two high-biosecurity chicken farms experienced outbreaks. Dead birds were found mostly near the barns’ air-intake vents.
Water sources were ruled out because all three farms had their own wells.
Samples from all three poultry farms were analyzed. Genetic data revealed that the outbreak strains were identical.
Aside from relative proximity, the three farms were completely unrelated. The duck farm didn’t share staff or contractors with chicken farms. According to the study, there were no large waterways near the chicken farms.
So how did the chickens become infected?
Data from the study suggests that a plume of contaminated air from the infected fattening duck farm made its way to the other farms.
Meteoric data indicate a breeze in the direction of the chicken farms, paired with cloudy conditions that may have kept the sun’s ultraviolet rays from killing the virus, along with virus-supporting cool air assisted the movement from the duck farm to the chicken farms.
Unfortunately, outbreak investigators did not conduct air sampling, so this theory cannot be proven.
While these scientists make a compelling case, others are not entirely convinced.
For example, David Swayne, DVM, PhD and retired poultry veterinarian and avian flu researcher with the US Department of Agriculture (USDA) Agriculture Research Service says that despite the hypothesis and supporting data being laid out quite well, their conclusion should be interpreted with caution.
“I think we, as veterinarians who deal with avian influenza and other infectious diseases, would acknowledge that there is some airborne – and I’ll use the word dissemination – and that may lead to transmission,” said Swayne. “But we have to be cautious to make sure people understand that it doesn’t mean that it’s the only way, nor that it’s the major way. And each individual facility is going to be different.
Another expert in the field, Montserrat Torremorell, DVM, PhD, and chair of the Department of Veterinary Population Medicine at the University of Minnesota described the researchers argument for airborne transmission “compelling.”
Meteorological conditions, timing, housing, and lack of other epidemiological links between the three premises are “supportive of airborne transmission in this case.”
In fact, Torremorell collected air samples in and outside of facilities during a bird flu outbreak in Minnesota. Air samples from five of the six flocks tested positive for large quantities of the virus. All viral samples were in the “active infection stage.”
A bird flu vaccine is already in use in China, France, Egypt, and Mexico. The USDA’s conditional approval of a killed H5N2 vaccine will likely be make its way to poultry farms in the United States very soon.
If you’d like to know more about food safety topics in the news, like “Can Bird Flu Spread by Wind? Experts Say, Maybe!,” check out the Make Food Safe Blog. We regularly update trending topics, foodborne infections in the news, recalls, and more! Stay tuned for quality information to help keep your family safe, while The Lange Law Firm, PLLC strives to Make Food Safe!
By: Heather Van Tassell (contributing writer, non-lawyer)