Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at February 24, 2016

Pneumonia is an inflammation of the lungs. It can be caused by bacteria, viruses or fungi, and may range from mild to life-threatening. Symptoms depend on the cause and severity of the disease, and treatment also varies.


Definition & Facts

The term pneumonia is generally used to indicate an inflammation of the air sacs in the lungs. The inflammatory process typically causes these sacs -- called alveoli -- to fill with fluid or purulent material called pus. As the alveoli fill, less lung space is available, so the patient becomes short of breath.

Pneumonia can be community-acquired pneumonia -- meaning the infection was contracted outside the hospital -- or hospital-acquired, meaning the infection occurred in a hospitalized patient and was not the reason why the patient was originally hospitalized. Pneumonia is most serious in infants, older adults and people with weakened immune systems or chronic health conditions.

Some people are at higher risk of pneumonia than others. Smokers, people on chemotherapy for cancer or those with lung diseases like asthma are at higher risk of pneumonia. Heart disease, HIV/AIDS, and chronic obstructive pulmonary disease also increase people's risk of pneumonia. Children under the age of two and adults over the age of 65 also have increased risk of pneumonia. People who are hospitalized in an intensive care unit, especially those on a ventilator, face an increased risk of hospital-acquired pneumonia.

Symptoms & Complaints

Symptoms may vary from mild to severe. If caused by an infection, symptoms typically include fever, and may include sweating or chills. In severe infections, the fever may be quite high: 102 degrees Fahrenheit (38.9 Celsius) or more. Cough is common, especially with exertion, and both chest pain and shortness of breath may occur.

Fatigue is another common symptom and may be one of the first signs of pneumonia. In some cases, the patient will also develop nausea, vomiting and diarrhea. Newborns and infants, however, can have pneumonia but not show any symptoms. Older adults or those in poor health may not have a temperature and may actually have a lower-than-normal temperature (normal is 98.6 degrees Fahrenheit or 37 degrees Celsius). One sign of possible pneumonia in the elderly is sudden changes in mental awareness, which may result from low levels of oxygen or a high fever.


Pneumonia usually results from an infection. Bacterial pneumonia in the US is most likely to be caused by an organism called Streptococcus pneumoniae. It may be associated with a common cold or the flu, or occur on its own. Another bacterium, Mycoplasma pneumoniae may cause an infection called “walking pneumonia,” or Mycoplasma pneumonia, a condition that isn't severe enough to require bed rest.

The same viruses that cause colds and flu can also cause pneumonia. This is the most common cause of the disease in children under the age of five. Most viral pneumonias are mild, although they have the potential to become serious. Fungal pneumonia usually occurs in people who have weakened immune systems. The causative organisms are found in bird droppings or soil.

Aspiration pneumonia is not an infection, but results from inhaling a substance like food or water into the lungs. Infants, near-drowning victims and people who have had a stroke are those most likely to develop aspiration pneumonia.

Diagnosis & Tests

The diagnosis of pneumonia is based on the patient's symptoms, X-rays and laboratory tests. Chest X-rays can show the fluid and inflammation in the lungs and pinpoint the location of the pneumonia. A chest X-ray doesn't determine the cause of the disease, however. If a more detailed picture of the lungs is needed, the doctor may order a CT scan, an imaging study that can show tiny details not seen on an X-ray.

A pulse oximetry can measure the oxygen levels in the blood. Although this test isn't diagnostic, it's an indication of how sick the patient is and how well the lungs are working. To identify the organism that is causing the disease, the doctor will usually order blood tests or sputum cultures. The blood and sputum specimens are examined under a microscope to identify the organisms that might be causing the symptoms.

In addition, lab personnel may try to grow the organisms -- called culturing -- to help identify them and determine whether they are susceptible to a particular antibiotic or antiviral drug. A pleural fluid culture is another way to determine what is causing the infection. The doctor inserts a needle between the ribs and into the tissue sac surrounding the lungs. The fluid obtained is examined and cultured as blood or sputum would be.

Treatment & Therapy

Treatment depends on the cause of the pneumonia and the symptoms. In mild cases, the patient may simply need to rest, drink plenty of fluids and take over-the-counter medications like acetaminophen, aspirin, or cough syrup. Infections caused by bacteria are usually treated with antibiotics. Antibiotics don't work against viral infections, but some antiviral medications may be used, depending on the actual virus.

Medications to loosen lung secretions, suppress coughs and decrease fever may be used in any type of pneumonia. People who are severely ill may need to be hospitalized to receive intensive respiratory therapy and intravenous medications. Respiratory therapists can administer inhaled medications that help expand the alveoli and loosen secretions. Some patients may need oxygen therapy. In extremely severe cases, the doctor may put a tube into the patient's airway and use a machine called a ventilator to assist the patient's breathing.

Prevention & Prophylaxis

A healthy immune system is the best prevention strategy when it comes to pneumonia. Basics like a healthy diet, adequate sleep and regular exercise promote a strong immune system. Regular hand washing can decrease the risk of infection. Smoking damages lung tissue and increases the risk of pneumonia and other lung diseases. Those who smoke should try to stop, to prevent not only pneumonia but also heart disease and lung cancer.

Vaccines are also available that target the pneumococcal bacteria that cause pneumonia as well as meningitis and other serious infections. These pneumococcal vaccines include pneumococcal conjugate vaccine and pneumococcal polysaccharide vaccine.