Pig-human chimeras have pig cells, human cells, AND novel fused cells containing mixed pig-human nuclei. And those fused cells can catch pig viruses that previously haven't crossed the species barrier.

It's a trans-species viral superhighway!

I wonder if they're testing these part-human pigs for above-average-pig intelligence. At some point I picture one of the pigs -- let's call him Wilbur -- surprising the experimenters with a fully vocalized "what the hell do you think you're doing?"