What Is Pneumonia?

Pneumonia is a serious lung infection. Many cases of pneumonia are caused by bacteria or viruses. Other causes include fungi, chemicals, and gases. Pneumonia may also appear after another illness, such as a cold, flu, or bronchitis. Those most at risk include the elderly and people with chronic health problems.

Healthy Lungs

• Air travels in and out of the lungs through tubes called airways.

• The tubes branch into smaller passages called bronchioles. These end in balloonlike sacs called alveoli.

• Blood vessels surrounding the alveoli absorb oxygen into the bloodstream. At the same time, the alveoli remove carbon dioxide from the blood. The carbon dioxide is then exhaled.

When You Have Pneumonia

• Pneumonia causes the bronchioles and the alveoli to fill with excess mucus and become inflamed.

• Your body's response may be to cough. This can help clear out the fluid.

• The fluid (or mucus) you cough up may appear green or dark yellow.

• The excess mucus may make you feel short of breath.

• The inflammation may give you a fever.

What Are the Symptoms?

Symptoms of pneumonia can come without warning. At first, you may think you have a cold or flu. But pneumonia symptoms may quickly worsen. Common symptoms include the following:

• Severe cough with uncontrolled spasms

• Fever and chills

• Coughing up mucus

• Shortness of breath

• Increased heart rate

• Chest pain or discomfort when breathing in or coughing.