Here is a website about parvo... http://www.animalclinic.com/parvo.htm

Unlike most other viruses, CPV is stable in the environment and is resistant to the effects of heat, detergents, and alcohol.
Due to its stability, the virus is easily transmitted via the hair or feet of infected dogs, contaminated shoes, clothes, and other objects. Direct contact between dogs is not required to spread the virus.
Dogs that become infected with the virus and show clinical signs will usually become ill within 7-10 days of the initial infection.
Young puppies less than five months of age are often the most severely affected and the most difficult to treat.
The best method of protecting your dog against CPV infection is proper vaccination.
As it says, pups under 5 months are the most difficult to treat. If you don't have enough money to care for these pups, find someone else to take them, because the treatment for three pups can take you into the thousands of dollars. Parvo virus can not be killed once the dog has it, so it's important that the pups are placed in a safer environment.