How could a virus come from a pig-sty? Even if in poor condition. Bacteria live for a long time in feces, virus don't.
A virus needs a live body to live body transfer, or at least a short term in a moist cool dark place.
Now I could see a transfer happening at slaughter. To kill, gut, and dismember an animal is a very intimate thing, you get covered in goo, there are aerosols of blood and other fluids. Yes, it's messy, and you're playing with sharp knives, cutting through bone and cartilage, leaving sharp edges to scrape yourself on... After all the hard work is done, you scrub and scrub, and you can't get the smell of blood off your body. It's much easier to call out a pro... But it's important to do it once or twice, you quickly learn a whole lot about anatomy.