What is pneumonia?
Pneumonia is an infection of one or both of the lungs caused by bacteria, viruses, fungi, or chemical irritants. It is a serious infection or inflammation in which the air sacs fill with pus and other liquid.
- Lobar pneumonia affects one or more sections (lobes) of the lungs.
- Bronchial pneumonia (also known as bronchopneumonia) affects patches throughout both lungs.
What causes pneumonia?
There are more than 30 different causes of pneumonia, and they’re grouped by the cause. The main types of pneumonia are:
- Bacterial pneumonia. This type is caused by various bacteria. The most common is Streptococcus pneumoniae. It usually occurs when the body is weakened in some way, such as by illness, poor nutrition, old age, or impaired immunity, and the bacteria are able to work their way into the lungs. Bacterial pneumonia can affect all ages, but you are at greater risk if you abuse alcohol, smoke cigarettes, are debilitated, have recently had surgery, have a respiratory disease or viral infection, or have a weakened immune system.
- Viral pneumonia. This type is caused by various viruses, including influenza (flu), and is responsible for about one-third of all pneumonia cases. You may be more likely to get bacterial pneumonia if you have viral pneumonia.
- Mycoplasma pneumonia. This type has somewhat different symptoms and physical signs and is referred to as atypical pneumonia. It is caused by the bacterium Mycoplasma pneumoniae. It generally causes a mild, widespread pneumonia that affects all age groups.
- Other pneumonias. There are other, less common pneumonias that may be caused by other infections, or that result from inhaling food, liquid, gases, dust, or fungi.
What are the symptoms of pneumonia?
The symptoms of bacterial pneumonia include:
- Cough that produces green, yellow, or bloody mucus
- Shaking chills
- Shortness of breath that gets worse with activity
- Low energy and extreme tiredness
- Loss of appetite
- Sharp or stabbing chest pain that’s worse with deep breathing or coughing
- Heavy perspiring
- Rapid pulse
- Rapid breathing
- Bluish color to lips and fingernails
- Confused mental state or delirium (especially in older people)
Early symptoms of viral pneumonia are the same as those of bacterial pneumonia, which may be followed by:
- Increasing shortness of breath
- Muscle pain
- Worsening of the cough
Mycoplasma pneumonia has somewhat different symptoms, which include a severe cough that may produce mucus.
How is pneumonia diagnosed?
Diagnosis is usually made based on your recent health history (such as surgery, a cold, or travel exposures) and the extent of the illness. Based on these factors, your health care provider may diagnose pneumonia simply on a thorough history and physical exam, but the following tests may be used to confirm the diagnosis:
- Chest X-ray. This test takes pictures of internal tissues, bones, and organs, including the lungs.
- Blood tests. This test may be used to see whether infection is present and if infection has spread to the bloodstream (blood cultures). Arterial blood gas testing checks the amount of oxygen in your bloodstream.
- Sputum culture. This test is done on the material that is coughed up from the lungs and into the mouth. It's often used to see if there's an infection in the lungs.
- Pulse oximetry. An oximeter is a small machine that measures the amount of oxygen in the blood. A small sensor is taped or clipped onto a finger. When the machine is on, a small red light can be seen in the sensor. The test is painless and the red light does not get hot.
- Chest CT scan. This imaging procedure uses a combination of X-rays and computer technology to produce sharp, detailed horizontal, or axial, images (often called slices) of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than regular X-rays.
- Bronchoscopy. This is direct exam of the bronchi (the main airways of the lungs) using a flexible tube (called a bronchoscope). It helps to evaluate and diagnose lu