A five-month-old puppy started having diarrhea the day before yesterday (still lively), yesterday began vomiting phlegm-like stuff, then stopped eating and drinking and became listless, and today has bloody stool and can’t walk.

Hello. From your description, the dog shows diarrhea, vomiting, no eating or drinking, lethargy, bloody stool, and inability to walk. If the dog isn’t fully vaccinated, these signs very likely mean distemper, parvovirus, or similar infectious disease. Take it to a vet promptly for viral screening and related tests to confirm the cause and treat it in time.

These infectious diseases are very harmful and seriously threaten the dog’s life; timely treatment is key. The dog needs professional hospital care—home treatment won’t work well and will only waste the best window for treatment.