Pneumonia and Influenza Flu and pneumonia are respiratory
illnesses that should not be taken lightly. In the U.S.,
pneumonia and the flu combined are the eighth leading cause of
death. Older adults are at greater risk than younger adults for
contracting pneumococcal pneumonia, the most common bacterial
form of the disease. Taking steps to prevent pneumonia,
recognizing the symptoms, and getting early treatment are vital
to maintaining good health. What is pneumonia? Pneumonia is an
inflammation of the lungs—either one or both—caused by an
infection. The inflammation makes it difficult for oxygen to
reach your blood. Pneumonia can have more than 30 causes, but
the five main culprits are bacteria, viruses, mycoplasma, other
germs such as fungi and parasites, and chemicals. The most
common form of pneumonia is caused by viruses; half of all
pneumonias fall into this category. Bacterial pneumonia can
develop after a case of the flu, when your immune system is weak
from fighting the flu virus. Bacterial pneumonia