A few questions about Parvo

We had two of the pups tested for parvo and came back negative. The symptoms were almost identical. Extreme dehydration ..complete loss of appetite ...blood in stool..also the inner intestine silica was being passed and visible in stools. Took two full weeks for the older pup to completly pull through. I had four on IV'S along with skin spot flushes every three hours ...still lost three. Vet diagnosed as corona. Not arguing Rueb I know you definatly know your biz all the way round but they were for sure 8 ways from Lufkin TSC. I recall specifically due to I was looking for the sevens and they were out so had to get the 8. They may have just accidentally had em hence they were suspected of being bad. One pup had already had two cycles prior to this and still nearly got him. Know it wasn't Parvo. Corona is only other I know with that close of symptoms.