Most canine coronavirus infections are sub-clinical and produce few clinical signs in dogs. Occasionally an infection may cause more severe symptoms, particularly in young puppies. The most typical sign associated with canine coronavirus is diarrhoea, typically sudden in onset, which may be accompanied by lethargy and decreased appetite. The stool is loose, with a fetid odour and orange tint. It may contain blood or mucus. If a puppy has a mixed infection, for instance both coronavirus and parvovirus, the illness will be more severe.