Parvo is cyclical, everyone does a good job vaccinating regularly, then the crazy "anti vaccination" nuts will crop up, scare the bejeezus out of a good number of people, so they stop vaccinating, give it a few years and then it is back more virulant than ever before. I have seen 2 massive outbreaks over the years, even had 2 rescues with it a few years apart, so unfortunately have some experience with Parvo. The virus will shed at different rates and strengths, and is unpredictable in nature. Its most common (and easiest) passed along manner is in shit, but as said earlier urine and saliva