Overview

Pneumonia and bronchitis are called lower respiratory diseases because they affect your lungs or the airways leading into the lungs. Upper respiratory diseases such as colds affect your nose, throat and sinuses.

Pneumonia

Pneumonia is an inflammation of the lung caused by bacteria, viruses or fungus. The air sacs in the lungs fill with pus or other liquid, and prevent enough oxygen from getting into your body. This keeps your cells from working as well as they should. Without the right treatment, this lack of oxygen can kill.

Death from pneumonia is rare among otherwise healthy people. Children, the elderly and people with AIDS or tuberculosis are vulnerable if pneumonia sets in. While better treatment has reduced the number of deaths in the United States, it's the seventh leading cause of death.

Types of pneumonia include bacterial, viral and mycoplasma. Less common is pneumonia called pneumocystis carinii. It's caused by a fungus and mostly strikes people with AIDS. Tuberculosis can also cause pneumonia.

Walking pneumonia isn't an exact medical term. But your doctor may use it to describe pneumonia that isn't severe enough for bed rest. Another term you might hear is double pneumonia, which means both lungs are affected. This is very common.

Bronchitis

Bronchitis is an inflammation of the lining of the bronchial tubes, the airways that connect the windpipe to the lungs. Bronchitis makes it harder for air to pass through the lungs. When these tubes get infected, they swell and mucus forms, causing you to cough mucus and wheeze.

Bronchitis can be acute or chronic. Acute means the condition comes on quickly and can cause severe symptoms, but only lasts a few weeks. Acute bronchitis is usually caused by viruses and affects most people at some point in their lives.

Chronic bronchitis usually affects people who smoke or are regularly exposed to secondhand smoke. Like emphysema, this condition is a type of chronic obstructive pulmonary disease (COPD). Chronic bronchitis is diagnosed if someone has a productive cough for three months at a time during two consecutive years. The bronchi are chronically inflamed and irritated. People with chronic bronchitis may be short of breath and are vulnerable to bacterial infections of the airway and lungs.

More than 11 million Americans are diagnosed with chronic bronchitis each year. The condition is more common in women. Chronic bronchitis affects people of all ages, but is higher in people older than 45. In 2000 more than 1,100 Americans died from chronic bronchitis.

Prognosis

Pneumonia can be serious, but it's an infection that can be treated easily without a hospital stay if caught early. Acute bronchitis usually goes away on its own. Chronic bronchitis is very serious and should be treated as soon as possible.

More on Pneumonia and Bronchitis

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This article was reviewed and updated June 2007.