cows can infect the inhalation virus -loaded aerosole with the highly pathogenic aviary influenza H5N1, according to a preliminary print source 1 on bio -xive. However, scientists say that this type of transmission is probably not a current outbreak among cattle in the United States.

H5N1 was first identified in Rinders in Texas in March 2024. Since then, the virus has been detected in 157 herds and 4 people who are in contact with cattle in 13 US states. Studies have indicated that the main transmission path in cows is carried out by infected milk that contaminates milking equipment.

Before the outbreak, researchers did not know that influenza-a viruses such as H5N1 could spread in cows. Scientists have expressed concerns that H5N1 should effectively spread over the respiratory system in cows, it would be more difficult to control and the risk of transmission to humans would increase, given the close contact of cows with people.

In order to better understand infections in cows, several teams carried out challenge studies in which they experimentally infected animals with H5N1. The first results of one of these studies were published on July 13th and have not yet been examined.

virus -loaded fog

Amy Baker and her colleagues from the US Agriculture Ministry (USDA) in Ames, Iowa, infected cows and calves with the specific H5N1 strain, which was isolated in the cattle in Texas at the beginning of the outbreak. They exposed four one -year -old female calves to virus -loaded fog by using a mask that covered the nose and mouth of the animals. All infected animals formed neutralizing antibodies against the virus, which confirmed that they were infected.

The infected calves showed mild symptoms, and the researchers areolated infectious virus in the upper respiratory tract of two of the four calves. The study results suggest that the virus in an environment in which hundreds of animals are kept in close contact could be spread over the airways.

But since the animals do not leave high quantities of virus in their airways, this is probably not a main source of distribution, says Thomas Peacock, a virologist at Imperial College London. However, it is possible that cows are infected indirectly via the airways by aerosolized virus, which is separated by the udder.

Wendy Barclay, a virologist at Imperial College London, agrees that, despite the small amount of infectious virus in the animals, despite their high H5N1 exposure, aerogenic transmission is probably not efficient and does not "explain what is currently happening".

Instead, the study contributes to previous work that indicated that the virus is mainly spread by infected milk, say researchers. "The transmission from udder to udder currently seems to be the most likely main path," says Peacock. "However, this does not mean that the virus cannot change if this outbreak continues to take place at the current pace," he says. "What we have to do now can be carefully observed."

The study mainly examined the susceptibility of cows for infections, not the transfer, which makes it difficult to draw conclusions about viral distribution, says Jürgen Richt, a veterinary virologist at Kansas State University in Manhattan. Richt has carried out their own beef experiments with colleagues in Germany, and the results should appear in a prime print within weeks.

clumped milk

Baker and her colleagues also infected cows in lactation with the virus by teating in the mammary glands of two three -year cows. Two days after the infection, the cows showed signs of inflammation of the mammary glands that were two weeks. They started producing less milk, and the milk was also yellow and thick.

The researchers discovered infectious virus in the mammary glands during the three weeks of the study and up to two weeks in the milk. These findings "indicate that the mammary gland and milk are the primary sources for the virus spread inside and between milk flocks," says the pre -print source.

Richt says that the study Spiegle is observed at farmers. In view of the small number of animals included in the studies, however, respiratory transfer cannot be excluded, he says.