Bird flu was detected in a pig, and it could be a tipping point threatening more human transmission

Earlier this year, it made an unexpected jump into US cattle herds.

Since then, H5N1 has even infected a few humans who work closely with livestock in the US. But there has been no sign of sustained human-to-human transmission. Pigs could change that.

Meet the first infected pig

The US Department of Agriculture reported that the infected pig was living in a “backyard farming operation” which is now quarantined.

Two other pigs on the farm have tested negative for H5N1, while results are still pending for two others. Poultry there have also tested positive.

“There is no concern about the safety of the nation’s pork supply as a result of this finding,” the USDA reported, saying that the pigs at this farm were not intended for commercial food supplies.

Because of the backyard setting, this case doesn’t pose the same major outbreak risk as an infection in a commercial pig farm.

“If it starts to spread from pigs to pigs, then it’s much more of a problem,” Florian Krammer, a flu virologist at Mount Sinai’s Icahn School of Medicine in New York, told STAT News. “If it ends up in large pig populations in the US similar to cows, I think this would be a disaster.”

Why pig infection could be a tipping point

Pigs play host to both bird flu viruses and human flu viruses. That makes them a dangerous playground for the two to swap genes.

Inside a pig, the H5N1 bird flu virus could pick up genetic mutations that help it adapt to better infect human bodies.

Genomic detective work

Schultz-Cherry was surprised by the pig news but, she said, “I guess I shouldn’t be.”

The virus is circulating in cattle, chickens, wild birds, and cats all over the country. Mice have tested positive.

Just sharing a drinking water source with these animals could put a pig at risk. The USDA reported that livestock and poultry on the Oregon farm shared water sources, shelter, and other equipment.

Now that officials have samples of the virus that infected the pig, they can sequence its genome. That could hint at which animal it first came from.

Scientists will likely look for mutations in the virus that could help it infect humans more easily, such as a tweak that makes it attach to more mammal-type receptors in a host animal’s cells.

“It was one pig,” Schultz-Cherry said. “But it is something that will lead to increased monitoring of the situation.”