Can bird flu spread through the wind? Experts say they cannot be excluded

Non-peer review study Biorxiv, published on the preprint server, suggests that highly pathogenic avian influenza (HPAI) virus that has been lost in chicken feces can be transmitted by wind.

The report states that the H5N1 bird flu in February 2024 was among unrelated commercial poultry farms located approximately 8 km (5 miles) away in the Czech Republic during the 2023-24 HPAI season. It focuses on the occurrence.

Since the latest H5N1 outbreak began in February 2022, the virus has caused deaths in more than 150 million American birds.

Ideal weather for sending

The cluster after killing 5,000 fattened ducks within two days on a 50,000 bird farm near a lake where wild ducks are frequently visited by frequent lakes where bird flu is a possible cause of outbreaks It has been identified. The rest of the poultry was culled. A week later, a fatal outbreak with a slow course of illness occurred mainly at two high-reproductive officer frugen farms where dead birds were found near the air intakes in the barn. The entire population was culled. Every farm had its own well.

Experts assume that the slow disease course in chicken barns is due to reduced H5N1 permeability in chickens, reduced concentrations of the virus across distances from duck farms, or due to residential conditions.

Researchers from Prague at the State Veterinary Institute reconstructed events using genetic, postoperative, weather and geographical data, and mechanisms of H5N1 transmission between poultry on at least two farms. It suggests that it is. The three H5N1 strains collected from birds from all three farms were genetically identical, with no large waterways near the poultry farm. Duck Farm did not share staff or contractors with chicken farms.

Our results suggest that contaminated plumes released from infected fattening duck farms are important vehicles for HPAI transmission, rather than dust generated during the excess.

Additionally, weather data revealed breezes in the direction of chicken farms, cloudy conditions, cloudy conditions that could prevent the sun's ultraviolet rays from killing the virus, and cold air that supports the virus. The team did not perform air sampling.

“Our results suggest that contaminated plumes released from infected fattening duck farms are an important vehicle for HPAI transmission, rather than dust generated during depopulation,” the study authors said. wrote. “They also promote feng shui infections below the minimum infectious dose at recipient sites, strongly implying the role of trapped, mechanically ventilated buildings with high population density when transmitting virus concentrations. It's there.”

The skyborn is not just the main mode of spreading

Principal research author Dr. Alexander Naggie was convinced of the role of windbone transmission in these outbreaks when he and his team confirmed the same identity of H5N1 strains on donor and recipient farms, and Cidrap I told News. Dissemination events and slow disease progression in chicken barns characterized by feed and water consumption before clinical signs appear.

“And more, the birds affected [dead chickens] “It was in the section closest to the inlet,” he said. “Finally, I've ruled out all the other plausible explanations.”

Dr. Michael Osterholm, PhD at the Center for Research and Policy for Infectious Diseases (CIDRAP) at the University of Minnesota, and director of CIDRAP (CIDRAP), publisher of CIDRAP News, said airborne communication is extremely important. A barn that occurs in one geographic area where human biosecurity cannot be involved as a reason for propagation. ”

In the past, he said the poultry industry was reluctant to allow airborne transmission because of its impact on its practices. The medical and public health community recognizes that SARS-Cov-2 transmission was also in the air. ”

Researchers did a very good job of laying out hypotheses and support data, but their conclusions should be interpreted carefully, and the US Department of Agriculture's retired poultry as a researcher on avian flu. Veterinarian Dr. DVM (DVM) said (USDA) Agricultural Research Services.

“I think we're acknowledging that we're in the air as veterinarians who deal with the flu and other infectious diseases in birds. “But we don't mean that it's the only way. We must be careful to understand that that is the main way, and individual facilities will be different.”

The University of Minnesota's Faculty of Veterinary Population Medicine, DVM, DVM, DVM, PhD, called the researchers' arguments about airborne power transmission “convincing.”

“Weather conditions, timing of infection, residential conditions for animals, susceptibility to infected animal populations, and lack of other epidemiological links between facilities support airborne transmission in this case,” she emailed. I stated.

During the Minnesota outbreak of avian influenza, Tremorel collected facilities both inside and outside the facility that houses three infected turkeys and three egg-sold chickens. Five of the six groups tested positive for large amounts of H5N1 viruses, all of which were in the active infection stage. Negative samples were from a herd at a high stage of depopulation.

“More positive samples were available in the facility and in the exhaust fans (~5m) [meters; 16 feet] (away from the facility), and the number of positive tests decreased with distance, but still about 150 m and 1 km[キロメートル]The suspect (tracks of RNA material) was identified. “About a half mile,” she said.[kilometer;roughlyahalfmile)”shesaid”Viablevirus(throughvirusisolation)wasfoundinsidethefacilitiesattheoutsideoftheexhaustfanandataabout100m”[kilometer;roughlyahalfmile)”shesaid”Viablevirus(throughvirusisolation)wasfoundinsidethefacilitiesattheoutsideoftheexhaustfanandatabout100m”

The entry mechanism is difficult to determine

Dr. David Stahl Knecht, professor emeritus at the University of Georgia School of Veterinary Medicine and wildlife expert, said the study provides an additional context. evidence some the study It suggests the spread of the windbone virus. However, he added that there is little identification of mechanisms for the transmission of disease to poultry homes, as there is no way to control the variables.

“It basically says it could have happened and I wouldn't dispute it,” he said. “But there's too much going on to bring in concrete evidence like an ly controlled experiment.”

“The flu can be transmitted in millions of different ways, but perhaps there's nothing we don't know,” he added. For example, whether the virus enters a poultry house through a raccoon, bird, person, or human shoe, “these types of details are never really resolved.”

Stallknecht said he and his team tried to study the water-based avian flu infections associated with ducks. “And we got to where we had to stop because the numbers and odds were so extreme,” he said. “We can't experiment to get a trillion events.”

Swayne said that equipment moving inside and outside the chicken barn and people inside and outside the chicken barn must be carried out with a very high level of biosecurity to prevent the spread of the virus. The barn is due to contamination around the outside, wild birds that deposit feces there when they eat, spilling grain silos feed, etc. ”

He added that just because the virus is transported through the wind doesn't necessarily mean entering the barn like that. “Virus can move particles and water droplets far away with the wind, landing and polluting the environment.”

The author was also skeptical at first.

Nagy acknowledges that the spread of the skyborne is not usually considered a major route of infection in poultry, and that windbone spreads require “many specific constellations” to conduct further research. I did.

“However, once all conditions are aligned, Feng Shui infections are a feasible spread mode, and could play a more important role than previously thought, especially in densely populated poultry areas,” he said. I said that. “The Windbone Route is important to consider when infections appear in new locations with no obvious links to other farms, or when disease or mortality is first observed near air bays. .”

Poultry operations usually consist of trapped, mechanically ventilated buildings with high population density and the situation remains unchanged.