Avian influenza, aka bird flu and designated as the H5N1 virus, may be poised to become the next pandemic…and be much deadlier than Covid was in 2020.

The virus was reported in U.S. dairy cows for the first time on March 25th, and has now spread to 34 herds in nine states, according to WebMD, which predicts little danger to humans—for now.

The first cases of this H5N1 bird flu strain emerged in North America among wild migratory birds in late 2021 and soon spread to poultry farms. It’s now showing up among dairy cows and at a major egg producer and one person who had close contact with cows has been infected. However no live virus has been detected in dairy product samples, seeming to confirm the belief that pasteurization kills the virus.

The current outbreak has affected many new wild bird species and persisted for longer than previous ones. The virus has also popped up more often in mammals, both in the wild and on farms, and at times led to a wave of infections and death.

“We are in fairly unprecedented, uncharted territory, globally in relationship to avian influenza,” says Dr. Peter Rabinowitz, director of the UW Center for One Health Research.

Currently it’s not clear exactly how bird flu is spreading among mammals, and to what extent infections are mostly happening after some kind of contact with infected birds.

But scientists worry about sustained mammal to mammal transmission of avian influenza because that gives the virus more opportunities to adapt to that host and acquire mutations that could make it better suited to mammals.

There have been large die offs of marine mammals in South America and a particularly alarming outbreak on a mink farm in Spain.

In both of those examples, the virus had evolved a couple of “mammal adaptive mutations” that haven’t yet been seen in cows, says Louise Moncla, a virologist at the University of Pennsylvania.

You can read more about this on the NY Times website here.