<Tr> <Th> Frequency </Th> <Td> 450 million (7%) per year </Td> </Tr> <Tr> <Th> Deaths </Th> <Td> 4 million per year </Td> </Tr> <P> Pneumonia is an inflammatory condition of the lung affecting primarily the small air sacs known as alveoli . Typically symptoms include some combination of productive or dry cough, chest pain, fever, and trouble breathing . Severity is variable . </P> <P> Pneumonia is usually caused by infection with viruses or bacteria and less commonly by other microorganisms, certain medications and conditions such as autoimmune diseases . Risk factors include other lung diseases such as cystic fibrosis, COPD, and asthma, diabetes, heart failure, a history of smoking, a poor ability to cough such as following a stroke, or a weak immune system . Diagnosis is often based on the symptoms and physical examination . Chest X-ray, blood tests, and culture of the sputum may help confirm the diagnosis . The disease may be classified by where it was acquired with community, hospital, or health care associated pneumonia . </P>

Pneumonia directly affects which part of the body