The original strain of H5N1, explains Wolfe, jumped directly from birds to humans. Other viruses, meanwhile, make the leap to domestic animals before infecting humans; that mixing can then introduce deadlier strains of unknown viruses into the world. “So what happens is you have a particular pig out there and it could get infected with two different viruses — maybe one that’s been in human and one that’s been in the original reservoir of a bird — and they can mix and match their genes and create mosaic daughter viruses that will have completely novel properties,” he says.
- via Fresh Air Interview with Nathan Wolfe: The Man Who Tracks Viruses Before They Spread
