The reason dogs keep screaming in the late stage of parvovirus is due to pain. Generally, dogs in the late stage of parvovirus have severe diarrhea and blood in their stools, which can cause abdominal pain and may also cause intestinal spasm, so dogs will have Screaming situation. The first three days of parvovirus are in the early stage, and the fourth and fifth days are in the middle and late stages. This is the most difficult time, and if the dog can persevere, it can recover.