If you have a dog or puppy check with your veterinarian as to when your pets vaccinations are due. Generally puppies receive a combo vaccination at 6-8 weeks of age, then a booster at 10-12 weeks and 14-16 weeks of age, and once a year there after. This combo vaccination covers many diseases, only one being parvo virus. If your puppy becomes lethargic and is vomiting and suffering with diarrhea see your veterinarian immediately, these are signs of parvo. Unfortunately, parvo strikes quickly and can become serious within 12 - 24 hours, puppies can die before the owners have a chance to realize how sick it is and the need for a veterinarian. If your puppy starts to show signs of parvo, don't wait for it to get better on it's own, get to a veterinarian. Also, shelter puppies are very prone to getting parvo because of the lack of vaccinations and the exposure to so many other dogs and puppies - don't let this stop you from adopting but think about pet insurance and shelter insurance if available, it may come in handy.