Sick dogs can be taken to the pet hospital for test strip testing after receiving serum to rule out infectious diseases. Generally, dog dealers will inject serum into sick and mentally ill dogs, which will make the dogs look more energetic. Most people cannot tell whether the dogs are abnormal, but if they persist for two days, the dogs will start to get sick or even die. Commonly known as the dog of the week, it is best not to buy a dog from an irregular place.