Pneumonia is an inflammation of the respiratory tract due to infection with viruses, bacteria, or fungi. It may cause the air sacs to fill with fluid or pus and cause symptoms such as cough with phlegm, difficulty breathing, and fever and chills. Atypical pneumonia is a type of pneumonia with much milder symptoms. Walking pneumonia is the nonmedical term for this type of pneumonia.
Most people with pneumonia are incapacitated for several days and may require hospitalization to recover fully. Atypical pneumonia is called walking pneumonia because a person can have it and still go about their daily activities without needing hospitalization. This is because it is caused by bacteria that are not as virulent as those in regular pneumonia. The most common  is Mycoplasma pneumoniae, but other bacteria and viruses can also cause it.
While atypical pneumonia is often much milder than typical pneumonia, the symptoms it causes can still be very uncomfortable. They also tend to last longer than regular pneumonia. Many people with walking pneumonia do not know they have it since the symptoms are hardly serious enough to warrant a chest X-ray. A chest X-ray is how pneumonia is diagnosed. The following are signs you may have walking pneumonia.