Pneumonia is a potentially fatal infection that causes inflammation (redness and swelling) inside the lungs, resulting in breathing difficulty.

Among the most vital organs, the lungs pump air in and out of the body so that blood can exchange carbon dioxide for the oxygen that it circulates through the body. When breathing in, air flows through the trachea (windpipe) and then into two branches called bronchi inside the lungs. In turn the bronchi subdivide almost 20 times into smaller and smaller passages creating numerous bronchioles (smaller airways). Each of these airways ends in a cluster of tiny air sacs called alveoli. This creates a vast amount of surface where the blood can collect oxygen inside a small space, the chest cavity.

When certain foreign materials, bacteria, fungi or viruses enter the body through the lungs and penetrate the natural defenses in the lungs, pneumonia can develop. What is commonly referred to as pneumonia is actually more than 50 variations of the condition, ranging from mild (such as "walking pneumonia") to life threatening. It may affect only one lung or both lungs (sometimes called double pneumonia). Pneumonia can occur independently, after certain illnesses (e.g., colds or influenza) or along with other illnesses.

More than 60,000 Americans die each year from pneumonia. It can strike people of any age, but it is of greatest risk to the elderly, infants and very young children and persons with chronic illnesses.


Although early treatment is the best way to recover fully and quickly, pneumonia is challenging to diagnose. It sometimes seems like a simple cold or the flu, and its signs can vary depending on what is causing the pneumonia. Symptoms include:

  • A persistent cough
  • An unexplained fever, especially one of 102° F or higher for several days in a row
  • Chest pain that changes with breathing
  • Chills and sweats
  • Shortness of breath
  • Suddenly feeling worse after a cold or influenza

Anyone with these symptoms should not hesitate to call a doctor. People who should be especially concerned with these symptoms include older adults and individuals who are undergoing chemotherapy, have a suppressed immune system, are taking drugs that suppress the immune system (e.g., prednisone), are affected by alcoholism, have been injured, are confined to bed or have heart conditions or other conditions that affect the ability to breathe.

Pneumonia can turn fatal within 24 hours under certain conditions. Seeking early treatment is important to ensure that the condition does not become life threatening.

Some complications that can occur with pneumonia are:

  • The lungs may swell because the disease can fill up the air spaces inside the lungs, making breathing difficult.
  • The infection that causes the pneumonia can spread into the bloodstream and then to other organs.
  • Fluid can collect between the lining (pleurae) of the lungs and the lining of the inside of the chest. When fluid collects inside it is called pleural effusion. This fluid can become infected (a condition known as empyema) and may need to be drained through a tube inserted between the ribs.


Causes and Risk Factors

Some of the organisms that cause pneumonia are commonly found in the air. The lung's natural defenses normally protect against infection from these organisms, but they sometimes break through these defenses. 

Pneumonia may be caused by:

Bacteria. The most common cause of pneumonia is bacterial infection, and many different bacteria can cause the condition, producing mild to severe cases. Bacterial pneumonia can occur independently or following illnesses, such as colds, flu or upper respiratory infections.

Fungi. Certain types of fungus can cause pneumonia. When the fungus is inhaled, some people develop symptoms of acute pneumonia, others develop a form that lasts for months, although most people experience few if any symptoms. Pneumocystis carinii, a yeast-like fungi that is known as an opportunistic infection because it usually affects individuals with compromised immune systems, such as those with AIDS or undergoing chemotherapy.

Viruses. Several different viruses can cause pneumonia, including some of the same viruses that cause influenza. This type of pneumonia usually hits in the fall and winter and is more serious in people with heart or lung disease. People who have viral pneumonia can also develop bacterial pneumonia.

Other microorganisms. In rare cases, other living organisms may be responsible for pneumonia. These organisms include amoebas and mycoplasmas (which have characteristics of both bacteria and virus).

Other foreign materials. Pneumonia can occur when food, mucus, vomit, chemicals or other substances enter the lungs. Called aspiration pneumonia, this condition can develop from accidentally inhaling substances during a seizure, unconsciousness or stroke.

Persons who are at greater risk of developing pneumonia include those who:

  • Abuse alcohol (Alcohol interferes with the action of the white blood cells, which fight infections.)
  • Abuse drugs (Injection of illegal drugs can put you at greater risk of getting infections that can affect your lungs.)
  • Are age 65 or older
  • Are smokers (smoke damages the air passages inside the lungs)
  • Are very young children (whose immune systems are not fully developed)
  • Have an impaired immune system due to chemotherapy, immunosuppressant drugs or illness
  • Have been exposed to certain chemicals or pollutants
  • Have certain diseases, such as HIV/AIDS, heart disease,  emphysema or diabetes
  • Have had the spleen removed
  • Live in areas where exposure to types of fungus is greater (An example is valley fever, which is widespread throughout Southern California and the desert of the Southwest. This fungus does not affect everyone who is exposed to it, but a few develop severe pneumonia.)


To diagnose pneumonia, doctors usually begin with a medical history and a physical examination. Often the medical history may indicate a risk of having pneumonia. During the examination, the doctor uses a stethoscope to listen for abnormal bubbling, cracking or rumbling sounds that may indicate thick liquid in the lungs or inflammation (swelling) from an infection.

The doctor may recommend a blood test to check the white blood cell count and to detect viruses, bacteria or other organisms. A phlegm sample may be tested to help determine the cause of the pneumonia.

The doctor may also recommend a chest X-ray to confirm the diagnosis and to note the location and spread of the infection. If the X-ray does not confirm pneumonia, more sophisticated imaging may be needed, such as computed tomography (CT) scan.


Because pneumonia has different causes and different degrees of seriousness, treatment will vary according to the type of pneumonia a person has. Prescribed treatment may include:

Antibiotics. Normally given for bacterial infections, antibiotics may also be prescribed for other types of pneumonia. Antibiotics should be taken for the complete period prescribed to prevent the infection from returning and to reduce the formation of antibiotic-resistant bacteria.

Bed rest. Stress and fatigue can weaken the immune system, which could allow a relapse.

Fluids. Drinking plenty of fluids, especially water, helps prevent dehydration and break up phlegm in the lungs.

Over-the-counter medications. These medications may be recommended to alleviate aches, pains, coughing and fever.

Oxygen. In severe cases involving breathing difficulty, oxygen may be administered for several days.

About four to six weeks after treatment for pneumonia, the doctor will probably schedule a follow-up visit. Because the lungs may still be infected, the doctor will track the patient's progress to prevent a relapse or complications. Patients who are not feeling better by that time may need more tests to find out why.



Pneumonia usually is not something that a person "catches" from other people. People with pneumonia, however, may want to stay away from those with compromised immune systems. People can develop pneumonia due to weakened resistance. The following may be helpful in avoiding pneumonia, especially for those at greater risk of developing it:

  • Do not smoke. Smoking damages the lungs' ability to protect against infections.
  • Get enough rest and moderate exercise, and eat a die rich in fruits, vegetables and whole grains. These measures boost strength and help protect against serious illnesses and infections.
  • Get vaccinated against pneumococcal pneumonia at least once after the age of 65. People with chronic lung or heart disease, diabetes or sickle-cell anemia and those with the spleen removed, on chemotherapy or who have a lowered immune system may want to discuss a pneumonia vaccination with their doctor. Prevnar®, a pneumonia vaccine, can help protect young children under the age of two or those who are older and have a special risk of getting pneumonia.
  • Get vaccinated against the flu every year because pneumonia can be a complication of having the flu.
  • Regularly wash hands, which come in contact every day with many germs, including those that cause pneumonia. Hand washing also helps reduce chances of getting colds and flu.