Pneumonia is an infection that causes the alveoli (air sacs) in the lungs to become inflamed. The alveoli may fill with fluid, making breathing difficult. Both bacteria and viruses can cause the infection. Bacterial pneumonia is generally the more serious form of the disease. Some fungi and certain organisms that resemble bacteria can also cause the disease.
Some conditions make it more likely that a susceptible person will develop pneumonia in certain circumstances. One of these conditions is the existence of chronic disorders such as asthma, COPD (chronic obstructive pulmonary disease), and heart disease.
Pneumonia often develops after someone has had a cold or the flu. Symptoms of pneumonia may resemble those of a cold or flu that doesn’t disappear when expected and becomes worse. A person may also notice chest pain while breathing, as I know from my experience with the disorder. Anyone with a respiratory problem that lasts for a long time or is severe should visit a doctor for a diagnosis and treatment.