A new investigation into current avian flu outbreaks on dairy farms describes in unprecedented detail how efficiently the virus spread among cows and from cows to other mammals, including cats and a raccoon.
It’s an indication that the virus is developing new capabilities that worry bird flu experts.
Bird flu affected more than 100 million wild waterfowl, commercial flocks and domestic birds in the US over the last few years. Its spread has put scientists on alert about the possibility that one day the virus could evolve to spread from person to person, triggering the next pandemic.
No human-to-human transmission has occurred yet, as far as researchers know. But the total number of cases among people continues to grow: Colorado state health officials confirmed three new cases of bird flu in people on Thursday, bringing the national total to 14.
The human cases have all occurred in farm workers infected after exposure to sick animals, and all but one were diagnosed within the past four months. Although little is still known about the three most recent infections, the remainder were mild.
The new study shows that the virus is spreading from one species of mammal to another – a relatively new phenomenon that could make it difficult for authorities to control.
The longer the virus remains uncontrolled, the greater its potential to evolve and adapt to become a greater threat to people, according to the authors of the new study, which was published in Nature magazine on Tuesday.
“The virus is not very efficient in human infection and human-to-human transmission, but if the virus continues to circulate in dairy cows and from dairy cows to other mammalian species, this could change,” said Diego Diel, author of the study and the study. director of the Virology Laboratory at Cornell University’s Animal Health Diagnostic Center. “It’s worrying.”
The new study evaluated the first outbreaks of bird flu among cows on nine farms in Texas, New Mexico, Kansas and Ohio, sampling the animals and then comparing the genetic similarity of the virus between them.
Researchers found that the virus, a specific strain of bird flu known as H5N1, spread quickly between farms. When infected cows were transferred from Texas to a different farm in Ohio, the virus was soon discovered in the Ohio cows. And genetic sequencing suggests that cats and a raccoon acquired the virus and died, likely after drinking raw milk.
Sick cows began to eat less feed, ruminate less, decrease milk production and produce discolored milk, the study says. On some affected farms, cows died at twice the normal rate.
Andrew Bowman, a professor of preventive veterinary medicine at Ohio State University who was not involved in the new study, said the research reflects the experience veterinarians have had on many U.S. farms.
“It matches the clinical picture,” Bowman said. “This is 100% what we saw on dairy farms. This is just the first real documentation published.”
The study reinforces evidence that handling or drinking unpasteurized milk is dangerous.
Diel said infected cows release incredible amounts of virus through their mammary glands when infected – in higher concentrations than the virus can easily be grown in the laboratory.
“It is extremely risky to drink raw milk,” Diel said.
Several studies have detected live H5N1 virus in raw milk and other showed that pasteurization inactivates the virusmaking commercially produced milk safe for consumption.
Farmers should not send milk with the possibility of contamination for production.
“Milk from sick cows should not go into the milk supply,” Bowman said.
As scientists continue to study the bird flu outbreak, Bowman said he will be interested in whether cows can transmit the virus before they start to appear sick, as well as whether the virus continues to spread from mammals that contract infections from cows.
This is the third episode in which the virus has spread rapidly among a group of mammals, said Anice Lowen, a virologist and professor at Emory University School of Medicine who was also not involved in the new study. Previously, viruses spread on mink farms It is between sea lions and seals last summer.
Cases in some mammals were severe and the virus caused mass deaths among sea lions It is stampsamong other species.
Lowen said health officials should also consider the risk of people becoming infected with H5N1 and seasonal flu at the same time this winter. When someone is infected with multiple influenza viruses, these viruses can undergo a process called reassortment, in which they exchange genetic information.
This process could provide viruses with a shortcut to evolve, potentially changing how they spread.
“The virus we now have in cows poses a relatively low risk to humans. The CDC said so and they are right,” Lowen said. “But where the risk is, in my mind, is viral evolution. They change when they adapt to new hosts. They change when they undergo a rearrangement and exchange genes.”
The Centers for Disease Control and Prevention declined to comment on the new research.
This article was originally published in NBCNews. with
