Pneumonia is not caused by a low fever, so it is not possible to say that a low fever can become pneumonia. When pneumonia is present, a low fever can occur. It is recommended that the patient go to the hospital for routine blood tests to see if the fever is caused by a bacterial or viral infection. If there is a wet rumble, it is possible that the patient has pneumonia. It is recommended that a chest X-ray be done to check if the patient is diagnosed with pneumonia, and antibiotics should be administered according to the pathogenic bacteria.