Pneumonia

is an infection of the lungs that is caused by bacteria, viruses, fungi, or parasites. It is characterized primarily by inflammation of the alveoli in the lungs or by alveoli that are filled with fluid (alveoli are microscopic sacs in the lungs that absorb oxygen). At times a very serious condition, pneumonia can make a person very sick or even cause death. Although the disease can occur in young and healthy people, it is most dangerous for older adults, babies, and people with other diseases or impaired immune systems.

In the United States, more than 3 million people develop pneumonia each year, and about 17% of these receive treatment in a hospital. Most people with pneumonia recover, but about 5% will succumb to the condition.




What causes pneumonia?


Bacteria and viruses are the primary causes of pneumonia. When a person breathes pneumonia-causing germs into his lungs and his body's immune system cannot otherwise prevent entry, the organisms settle in small air sacs called alveoli and continue multiplying. As the body sends white blood cells to attack the infection, the sacs become filed with fluid and pus - causing pneumonia.

Pneumonia has bacterial, viral, fungal, and other primary causes. A summary is provided below.

Bacterial

Streptococcus pneumoniae is the most common cause of bacterial pneumonia. People who suffer from chronic obstructive pulmonary disease (COPD) or alcoholismmost often get pneumonia from Klebsiella pneumoniae and Hemophilus influenzae. Atypical pneumonia, a type of pneumonia that typically occurs during the summer and fall months, is caused by the bacteria Mycoplasma pneumoniae. People who have Legionnaire's disease caused by the bacterium Legionella pneumoniae (often found in contaminated water supplies and air conditioners) may also develop pneumonia as part of the overall infection. Another type of bacteria responsible for pneumonia is called Chlamydia pneumoniae. Pneumocystis carinii pneumonia is a form of pneumonia that usually affects both lungs and is found in patients with weakened or compromised immune systems from such conditions as cancer and HIV/AIDS and those treated with TNF (tumor necrosis factor) for rheumatoid arthritis.

Viral

Viral pneumonias are pneumonias that do not typically respond to antibiotictreatment (in contrast to bacterial pneumonias). Adenoviruses, rhinovirus, influenzavirus (flu), respiratory syncytial virus (RSV), and parainfluenza virus are all potential causes of viral pneumonia. 


Fungal

Histoplasmosis, coccidiomycosis, blastomycosis, aspergillosis, and cryptococcosis are fungal infections that can lead to fungal pneumonia. These types of pneumonias are relatively infrequent in the United States.

Nosocomial and others

Organisms that have been exposed to strong antibiotics and have developed resistance are called nosocomial organisms. If they enter the lungs, a person may develop nosocomial pneumonia. Resistant bacteria are often found in nursing homes and hospitals. An example is MRSA, or methicillin-resistant Staph aureus, which can cause skin infections as well as pneumonia. Similarly, outbreaks of the H5N1 influenza (bird flu) virus and severe acute respiratory syndrome (SARS) have resulted in serious pneumonia infections. Anthrax, plague, and tularemia also may cause pneumonia, but their occurrences are rare.

Who gets pneumonia?

Some people are more likely than others to develop pneumonia. Individuals at higher risk include those who:

• Smoke.
• Abuse alcohol.
• Have other medical conditions, such as chronic obstructive pulmonary disease (COPD), emphysema, asthma, or HIV/AIDS.
• Are younger than 1 year of age or older than 65.
• Have a weakened or impaired immune system.
• Take medicines for gastroesophageal reflux disease (GERD).
• Have recently recovered from a cold or influenza infection.
• Are malnourished.
• Have been recently hospitalized in an intensive care unit.
• Have been exposed to certain chemicals or pollutants.
• Are Native Alaskan or certain Native American ethnicity.
• Have any increased risk of breathing mucus or saliva from the nose or mouth, liquids, or food from the stomach into the lungs.

What are the symptoms of pneumonia?

Symptoms of pneumonia caused by bacteria usually come on more quickly than pneumonia caused by virus. Elderly persons and small children may actually have fewer or more mild symptoms than expected for such high risk groups. Most people with pneumonia begin with cold and flu symptoms and then develop a high fever, chills, and cough with sputum.


Although symptoms may vary greatly depending on other underlying conditions, common symptoms include:

• Cough
• Rusty or green mucus (sputum) coughed up from lungs
• Fever
• Fast breathing and shortness of breath
• Shaking chills
• Chest pain that usually worsens when taking a deep breath (pleuritic pain)
• Fast heartbeat
• Fatigue and feeling very weak
• Nausea and vomiting
• Diarrhea
• Sweating
• Headache
• Muscle pain
• Confusion or delirium
• Dusky or purplish skin color (cyanosis) from poorly oxygenated blood

How is pneumonia diagnosed?

A pneumonia diagnosis usually begins with a physical exam and a discussion about your symptoms and medical history. A doctor may suspect pneumonia if they hear coarse breathing, wheezing, crackling sounds, or rumblings when listening to the chest through a stethoscope.


Chest x-rays and blood tests may be ordered to confirm a pneumonia diagnosis. A chest x-ray can confirm pneumonia and determine its location and extent in the lungs. Blood tests measure white blood cell count to determine the severity of pneumonia and can be used to determine whether the infection is bacterial, viral, fungal, etc. An analysis of sputum also can be used to determine the organism that is causing the pneumonia.


A more invasive diagnostic tool is the bronchoscopy - a procedure whereby the patient is under anesthesia and a thin, flexible, and lighted tube is inserted into the nose or mouth to directly examine the infected parts of the lung.

How is pneumonia treated?

Pneumonia treatments depend on the type of pneumonia and the severity of symptoms. Bacterial pneumonias are usually treated with antibiotics, whereas viral pneumonias are treated with rest and plenty of fluids. Fungal pneumonias are usually treated with antifungal medications.


Over-the-counter medications are also commonly prescribed to better manage pneumonia symptoms. These include treatments for reducing fever, reducing aches and pains, and suppressing coughs. In addition, it is important to get plenty of rest and sleep and drink lots of fluids.


Hospitalization for pneumonia may be required if symptoms are especially bad or a patient has a weakened immune system or other serious illness. At the hospital, patients generally are treated with intravenous antibiotics and possibly put on oxygen.

How can pneumonia be prevented?

There are several ways to prevent pneumonia. There are two vaccines that are available to prevent pneumococcal disease (the bacterial infection that is the most common cause of pneumonia): pneumococcal conjugate vaccine (Prevnar) and pneumococcal polysaccharide vaccine (Pneumovax). Prevnar is generally administered as part of the normal infant immunization procedure and is recommended for children less than 2 years of age or between two and four years with certain medical conditions. Pneumovax is provided for adults who are at increased risk of developing pneumococcal pneumonia, such as the elderly, diabetics, those with chronic heart, lung, or kidney disease, alcoholics, smokers, and those without a spleen. The pneumonia vaccine may not completely prevent older adults from getting pneumonia, but it can reduce the severity of a future pneumonia.


In addition to vaccinations, physicians recommend that people wash hands, refrain from smoking, eat healthfully, exercise, and stay away from sputum or cough particles from others with pneumonia.