Researchers will try to stem the spread of pig-borne viruses by keeping the pigs in sterilized environments, not an ordinary feedlot. However, Bach says that won't eliminate at least one virus known as the Porcine Androgonous Retrovirus. Like the human immunodeficiency virus that causes AIDS, it moves into the genetic material of cells. Bach says there's no evidence so far of the retrovirus passing to human cells in the laboratory, but he says attempting a pig to human transplant would be the wrong way to find out if it could happen. We don't know the extent of risk.
Many people say it's very small.
I don't know what that means. And to be honest, I think if they were asked they wouldn't know either in quantitative terms. But we have to remember that if it were to occur, the results are catastrophic. If we say that, if it were to occur, that is the release of a pandemic, we may not recognize that for 10 years that it's happened, and then it'll burst on the scene. Bach worries that someone might move to clinical trials of xenotransplants too quickly in the pursuit of profits or prestige.