Pneumonia is a breathing (respiratory) condition in which there is an infection of the lung.

This article covers pneumonia in people who have not recently been in the hospital or another health care facility (nursing home or rehab facility). This type of pneumonia is called community-acquired pneumonia, or CAP.

See also: Hospital-acquired pneumonia

Bronchopneumonia; Community-acquired pneumonia; CAP

Pneumonia is a common illness that affects millions of people each year in the United States. Germs called bacteria, viruses, and fungi may cause pneumonia.

Ways you can get pneumonia include:

• Bacteria and viruses living in your nose, sinuses, or mouth may spread to your lungs.
• You may breathe some of these germs directly into your lungs.
• You breathe in (inhale) food, liquids, vomit, or fluids from the mouth into your lungs (aspiration pneumonia)

Pneumonia caused by bacteria tends to be the most serious kind. In adults, bacteria are the most common cause of pneumonia.

• The most common pneumonia-causing germ in adults is Streptococcus pneumoniae (pneumococcus).
• Atypical pneumonia, often called walking pneumonia, is caused by certain other bacteria.
• Pneumocystis jiroveci pneumonia is sometimes seen in people whose immune system is not working well.

Many other bacteria can also cause pneumonia.

Viruses are also a common cause of pneumonia, especially in infants and young children.

Risk factors that increase your chances of getting pneumonia include:

• Chronic lung disease (COPD, bronchiectasis, cystic fibrosis)
• Cigarette smoking
• Dementia, stroke, brain injury, cerebral palsy, or other brain disorders
• Immune system problem (during cancer treatment or due to HIV/AIDS or organ transplant)
• Other serious illnesses, such as heart disease, liver cirrhosis, or diabetes mellitus
• Recent surgery or trauma
• Surgery to treat cancer of the mouth, throat, or neck

The most common symptoms of pneumonia are:

• Cough (with some pneumonias you may cough up greenish or yellow mucus, or even bloody mucus)
• Fever, which may be mild or high
• Shaking chills
• Shortness of breath (may only occur when you climb stairs)

Other symptoms include:

• Confusion, especially in older people
• Excess sweating and clammy skin
• Headache
• Loss of appetite, low energy, and fatigue
• Sharp or stabbing chest pain that gets worse when you breathe deeply or cough

If you have pneumonia, you may be working hard to breathe, or breathing fast.

The health care provider will hear crackles or abnormal breath sounds when listening to your chest with a stethoscope. Other abnormal breathing sounds may also be heard through the stethoscope or by tapping on your chest wall (percussion).

The health care provider will likely order a chest x-ray if pneumonia is suspected.

You may need other tests, including:

• Arterial blood gases to see if enough oxygen is getting into your blood from the lungs
• CBC to check white blood cell count
• CT scan of the chest
• Culture of your sputum to look for the bacteria or virus that is causing your symptoms
• Pleural fluid culture if there is fluid in the space around the lungs

Less often patients may need:

• Bronchoscopy--a flexible tube with a lighted camera on the end passed down to your lungs
• Thoracentesis--removing fluid from the space between the outside lining of the lungs and the chest wall

Your doctor must first decide whether you need to be in the hospital. If you are treated in the hospital, you will receive:

• Fluids and antibiotics in your veins
• Oxygen therapy
• Breathing treatments (possibly)

It is very important that you are started on antibiotics very soon after you are admitted (unless you have viral pneumonia).

You are more likely to be admitted to the hospital if you:

• Have another serious medical problem
• Have severe symptoms
• Are unable to care for yourself at home, or are unable to eat or drink
• Are older than 65 or a young child
• Have been taking antibiotics at home and are not getting better

However, many people can be treated at home. Your doctor may tell you to take antibiotics. Antibiotics help some people with pneumonia get better.

• Don't miss any doses. Take the medicine until it is gone, even if you start to feel better.
• Do NOT take cough medicine or cold medicine unless your doctor says it is okay. Coughing helps your body get rid of mucus from your lungs.

Breathing warm, moist (wet) air helps loosen the sticky mucus that may make you feel like you are choking. These things may help:

• Place a warm, wet washcloth loosely over your nose and mouth.
• Fill a humidifier with warm water and breathe in the warm mist.
• Take a couple of deep breaths two or three times every hour. Deep breaths will help open up your lungs.
• Tap your chest gently a few times a day and lie with your head lower than your chest. This can help bring up mucus from the lungs.

Drink plenty of liquids (as long as your health care provider says it is okay):

• Drink water, juice, or weak tea
• Drink at least 6 to 10 cups a day
• Do NOT drink alcohol

Get plenty of rest when you go home. If you have trouble sleeping at night, take naps during the day.

With treatment, most patients will improve within 2 weeks. Elderly or very sick patients may need longer treatment.

Those who may be more likely to have complicated pneumonia include:

• Older adults or very young children
• People whose immune system does not work well
• People with other, serious medical problems such as diabetes or cirrhosis of the liver

In rare cases, more severe problems may develop, including:

• Life-threatening changes in the lungs that require a breathing machine
• Fluid around the lung (pleural effusion)
• Lung abscesses

Your doctor may want to make sure your chest x-ray becomes normal again after you are treated. However, it may take many weeks for your x-ray to clear up.

Call your doctor if you have:

• A cough that brings up bloody or rust-colored mucus
• Breathing (respiratory) symptoms that get worse
• Chest pain that gets worse when you cough or breathe in
• Fast or painful breathing
• Night sweats or unexplained weight loss
• Shortness of breath, shaking chills, or persistent fevers
• Signs of pneumonia and a weak immune system (for example such as with HIV or chemotherapy)

Wash your hands often, especially after:

• Blowing your nose
• Going to the bathroom
• Diapering

Also wash your hands before eating or preparing foods.

Don't smoke. Tobacco damages your lung's ability to ward off infection.

Vaccines may help prevent some types of pneumonia. They are even more important for the elderly and people with diabetes, asthma, emphysema, HIV, cancer, or other long-term conditions:

• Flu vaccine prevents pneumonia and other problems caused by the influenza virus. It must be given each year to protect against new virus strains.
• Pneumococcal vaccine (Pneumovax, Prevnar) lowers your chances of getting pneumonia from Streptococcus pneumoniae.

If you have cancer or HIV, talk to your doctor about ways to prevent pneumonia and other infections.

Centers for Disease Control and Prevention. Recommended adult immunization schedule--United States, 2012. MMWR. 2012;61(4)

Limper AH. Overview of pneumonia. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier;2011:chap 97.

Niederman M. In the clinic. Community-acquired pneumonia. Ann Intern Med. 2009;151(7).

Torres A, Menandez R, Wunderink R. Pyogenic bacterial pneumonia and lung abscess. In: Mason RJ, Broaddus VC, Martin TR, et al. Murray & Nadel's Textbook of Respiratory Medicine. 5th ed. Philadelphia, Pa: Saunders Elsevier; 2010:chap 32.