As I understand it the guy in the article bought a bunch of piglets from someone in China. I suspect the virus came with the bundle.
Remember when Hoof and mouth disease was rampant in Europe a few years ago?
Some American Animal Rights people went there and tromped through the infected barns, then tried to re-enter the US with the diseased manure on their shoes.
It was believed they wanted to introduce the disease to the US to destroy the meat industry here.