New mutation identified in avian influenza virus

A new study shows that the avian influenza virus raging on dairy farms in multiple states has acquired dozens of new mutations, some of which have made it more adept at transmitting between species, and antiviral drugs are now available. It also includes mutations that may make it less susceptible.

None of the mutations in and of itself warrants alarm. But experts said they stressed that the virus could evolve and be easily transmitted between people as the outbreak continues.

“Influenza mutates all the time. It's, in a sense, the flu mutating,” said Richard Webby, an influenza expert at St. Jude Children's Research Hospital who was not involved in the study.

“The real key is whether we start to see some of these variants becoming more prevalent,” Dr. Webby said. “That would increase the risk level.”

The virus, known as H5N1, has infected cows in at least 36 herds in nine states, raising concerns that milk could be infected. to make it rest And crowded farms highlight the risk of cross-species transmission of many viruses.

The research is posted online It was published Wednesday and has not been peer-reviewed. This is one of the first details of the Department of Agriculture's investigation, which until now has been largely opaque. Frustrated expert outside of government.

The outbreak began about four months before it was identified in late March and likely spread unnoticed through cattle with no visible symptoms, researchers found.the timing is consistent with estimates from genetic analyzes by other scientists.

The authors say the virus has been detected in some dairy herds, although the link to the affected farms is unclear, supporting the idea of ​​transmission from asymptomatic cows, and adding that the virus has been detected in some dairy herds, supporting the idea of ​​transmission from asymptomatic cows, and that there are still unidentified infected herds. This suggests that there may be.

The widespread nature of the outbreak suggests it is spreading efficiently among cattle, the new paper says. That can pose a significant risk to people who interact closely with those animals.

“The fact that it's been circulating in cattle for some time is definitely concerning,” said Louise Moncla, an evolutionary biologist who studies avian influenza at the University of Pennsylvania and was not involved in the study. It's something that should be done.”

“I'm very concerned about whether we can reliably find people who are infected,” she said.

In the new study, researchers collected samples containing the virus from 26 dairy farms in eight states. Cattle are usually not susceptible to this type of influenza, but the H5N1 strain appears to have acquired a mutation in late 2023, allowing it to jump from wild birds to cattle in the Texas Panhandle, researchers said. Ta.

The virus then appears to have spread to dairy farms from Texas to Kansas, Michigan and New Mexico. Since then, the H5N1 virus has leaked from cows to wild birds, poultry, domestic cats and raccoons at least a dozen times.

The findings should prompt extensive surveillance not only of affected farms, but also of farms with no reported infections, said Diego Diehl, a Cornell University virologist and study author. the doctor said.

Many of the other species probably became infected after coming into contact with contaminated milk, which may contain very high levels of the virus, Dr. Diehl said.Another study published earlier this week found that about 12 cat fed raw milk He was dead.

It is not uncommon for dairy farms to dump waste milk into manure pits or lagoons. It “definitely has the potential to be a source of infection for other susceptible species,” he says.

Researchers are closely monitoring the H5N1 gene sequence in cattle for mutations that could allow the virus to more easily infect or spread to mammals, including humans.

The only person diagnosed with bird flu during the current outbreak carried a virus with mutations that allowed it to infect humans more efficiently. One of his cows in the study also carried his H5N1 with that mutation. More than 200 of her other people were infected with a version of the virus that had a different mutation that provided the same benefits.

Veterinarians began observing an unexplained drop in the cow's milk production in late January and sent samples for testing.The Department of Agriculture did not do so. Check for infection Until March 25th.

“The more prevalent the H5N1 virus becomes, the more likely we are to encounter combinations of mutations that may increase the risk to humans,” said Jesse Bloom, an evolutionary biologist at the Fred Hutchinson Cancer Center in Seattle. Stated.

“On the other hand, H5N1 has been circulating in various species for more than 20 years, causing sporadic human infections, but no pandemics have occurred so far,” he said. “This is one of those situations that could happen next week or never happen.”