The bird flu is spreading alarmistically

What if airborne transmission is restricted through ferrets and cattle? Insights from Texan farm workers on H5N1 and other bird flu cases

She says overall there’s still very limited evidence for transmission through the air: “The fact that ferrets transmit pretty consistently in contact exposure is a bit concerning, but these results don’t throw up a lot of red flags for me.”

The results are “very preliminary” and what happens under controlled lab conditions isn’t necessarily indicative of what can happen in the wild, he says. “We certainly don’t see any changes that would suggest that there’s any way to support efficient airborne transmission.”

The unlikely spread among cattle and one dairy worker has scientists looking through the data to better understand this spillover. They say the risk to humans hinges on whether the virus can evolve in key ways to better infect mammals.

They found that variant had a “high capacity to cause fatal disease” among the animals and that it showed enhanced ability to replicate in human cells cultured in the lab, but “did not exhibit productive transmission in respiratory droplets” or via contaminated surfaces when tested in animals.

H5N1 is not a new virus. It was first discovered in chickens in Scotland way back in 1959 and over the next 10 years it was found in 23 countries, with a case fatality rate of 52 percent. The subtype that infected the Texan farm worker, known as 2.3.4.4b, has been spreading in the wild on an unprecedented scale over the past four years. The bird flu has killed hundreds of millions of birds and mammals in 26 countries since 2020, according to reports. The strain of H5N1 that is spreading so far and wide has reached many animals, including polar bears.

But this kind of reasoning may not fully explain mass infection events in some mammals, including “unprecedented” die-offs of seals and sea lions in South America and an outbreak on a mink farm in Spain.

There are still big questions about exactly how bird flu plays out in cattle, since it’s only now being followed closely. “There certainly are many mutations that occurred with this jump from wild birds into cattle and we don’t necessarily understand what they mean,” says Hill.

The next pandemic of poliovirus in mammals is a problem of cosmic evolution, says Dr. Danielle MacIntyre

She says the changes need to come together to support efficient spread in mammals. Of course, she adds, “there’s potentially other factors that we don’t yet understand.”

MacIntyre says thevirus is difficult to transmit between humans. A human Pandemic could be caused by a one of three things: a defect in the human respiratory tract, a glitch in the virus’s affinity with the lungs or a combination of the two.

Nichola Hill, a disease ecologist at the University of Massachusetts Boston, said this is a clue that the virus is evolving to better replicate inside a mammal but it’s not enough to make the virus transmit more easily between humans.

According to Darwyn Kobasa, head of high containment respiratory Viruses at Canada’s National Microbiology Laboratory, that is the main barrier that prevents this from becoming a virus that can spread efficiently between people.

He says it takes “a very, very high dose” and that it’s probably exposure to the processes that aerosolized the virus that sets it in motion.

It would need to become better at spreading through the air, like humans are capable of doing. When chickens are being slaughtered, bird flu often is linked to direct contact with an animal, according to David Swayne, who used to work for the USDA.

“It needs a small group of markers to coordinate across different genes for it to be this breakthrough and the next pandemic,” she says.

Genetic sequencing of the virus in the​​ Texas dairy worker showed it had undergone a mutation in a gene, PB2, that commonly gets affected when the virus infects mammals.

“We really need to keep on top of this, because I think we are at a bit of a precipice where something interesting or unfortunate could happen,” says Michelle Wille, a senior research fellow at the Center for Pathogen Genomics at the University of Melbourne.

How unusual is this influenza outbreak in herds of cattle? A professor of comparative pathology at the Universia University Medical Center

“I want to emphasize really how unusual this is,” says Thijs Kuiken, a professor of comparative pathology at Erasmus University Medical Center. The respiratory disease that these cattle have seems to be different to the one that other mammals with the Influenza Viruses have.

Instead, federal health officials investigating the outbreak suspect some form of “mechanical transmission” is responsible for spreading the virus within the herd. The theory is that high concentrations of virus are found in the milk and may be happening during the process of milking the cows.

The CDC warned doctors to be cautious in regards to any patients with acute respiratory symptoms or sore eyes who had recently been in contact with animals.