Lung Disease & Respiratory Health Center

Understanding Pneumonia -- the Basics

What Is Pneumonia?

Pneumonia is an inflammation of the lungs. Usually the inflammation is caused by an infection, but it can also be caused by breathing certain chemical fumes. It's a more common problem than most people think. Usually pneumonia is a mild disease, but some forms are very dangerous. In all cases, you'll need a doctor's advice.

Pneumonia can affect just one lobe of the right or left lung, a whole lung, or both lungs.

Many different kinds of germs infect the lungs and cause pneumonia. Infected lungs leak fluids and shed dead cells. This material clogs up air sacs and makes it hard for the lungs to do their job of getting oxygen into the blood. Without enough oxygen, none of the cells in your body work as they should.

Pneumonia generally lasts about two weeks. Even healthy people may feel tired or weak for a month or more after the lungs clear up.

What Causes Pneumonia?

Viruses cause many cases of pneumonia, but bacteria are the most common cause of pneumonia in adults over the age of 30. Fungi can also cause pneumonia.

Many of these germs are all around us. They usually can't get past a healthy person's natural defenses. Pneumonia is most common in those with weaker or compromised immune systems, such as elderly people, cigarette smokers, alcoholics, and people suffering from other diseases such as the flu.