Ok add this to the bathroom floor analogy.
What do you think is at the vets office or the emergency vets office??
Yup sick animals. I see people letting their dogs walk in on leashes. Mine are in carriers in the vets and only come out onto the clean table then right back into the carrier. The carrier never touches a floor or a chair.
Parvo can stay on surfaces inside and out in all kinds of weather and live for MONTHS!! At the vet office they clean tables in between pets but only do the floor once a day. When mine are there for surgery my vet knows the carrier is on a towel and my pups stay in the carrier before and after surgery. I do not want to bring anything home besides what I came in with (well less the ummm parts being removed)
So when you put your pup in the cart at petco or any other store, remember that the doggy before you was in the cart too. Hopefully he did not have giardia or even worse parvo....