Pneumonia Pneumonia is an infection of one or both of the lungs caused by bacteria, viruses, or fungi. The groups, that are at the highest risk include adults ages 65 and older, children younger than age 2, people with certain medical conditions and the persons that smoke. Antibiotics are used for bacterial pneumonia and severe cases may require hospitalization. Most viral pneumonias don’t have specific treatment. They usually get better on their own. The flu is a common cause of pneumonia. Because of that, getting a flu shot every year can help prevent both the flu and pneumonia. There is also a pneumococcal vaccine which can protect from a common form of bacterial pneumonia.