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Patient education: Pneumonia in adults (Beyond the Basics)

Thomas J Marrie, MD
Thomas M File, Jr, MD
Section Editors
John G Bartlett, MD
Julio A Ramirez, MD, FACP
Deputy Editor
Sheila Bond, MD
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Pneumonia is an infection of the lungs. It is a serious illness that can affect people of any age, but it is most common and most dangerous in very young children, people older than 65, and in those with underlying medical problems such as heart disease, diabetes, and chronic lung disease. There is seasonal variation with more cases occurring in the winter months.

This article will focus on community-acquired pneumonia (CAP), which refers to pneumonia that develops in people in the community rather than in a hospital, nursing home, or assisted-living facility. About four million cases of CAP occur each year in the United States, and approximately 20 percent of people with CAP require hospitalization.


During normal breathing, air is inhaled through the nose and mouth and travels through the trachea and the bronchi to the bronchioles. At the end of the bronchioles, there are small air sacs, called alveoli. Alveoli have thin, porous walls that contain tiny blood vessels called capillaries (figure 1).

The mouth and respiratory tract are constantly exposed to microorganisms as air is inhaled through the nose and mouth. However, the body's defenses are usually able prevent microorganisms from entering and infecting the lungs. These defenses include the immune system, the specialized shape of the nose and pharynx (which helps trap microorganisms and particulate matter in the air, thereby preventing them from entering the lungs), the ability to cough, and fine hair-like structures called cilia located on the bronchi. The cilia help remove particles or bacteria that enter the bronchi by a beating motion that moves the material up to the trachea, where it is coughed out. You can develop pneumonia if your defenses are not adequate, you are exposed to a particularly strong microorganism, or you are exposed to a very large number of microorganisms.

As the microorganisms multiply, your immune system responds by sending white blood cells to the alveoli. The infected alveoli become inflamed (filled with white blood cells, proteins, fluid, and red blood cells). These changes lead to the symptoms of pneumonia. (See 'Pneumonia symptoms' below.)


Some groups of adults are at a greater risk of developing pneumonia. These include people who:

Are older than 65 years

Smoke cigarettes

Are malnourished due to health conditions or lack of access to food

Have underlying lung disease, including cystic fibrosis, asthma, or chronic obstructive pulmonary disease (emphysema)

Have other underlying medical problems, including diabetes or heart disease

Have a weakened immune system due to HIV, organ transplant, chemotherapy, or chronic steroid use

Have difficulty coughing due to stroke, sedating drugs or alcohol, or limited mobility

Have had a recent viral upper respiratory tract infection including influenza


Pneumonia can be caused by a variety of microorganisms, including viruses, bacteria, and, less commonly, fungi. The most common bacterial cause of pneumonia in the United States is Streptococcus pneumoniae (also called pneumococcus). Other bacterial causes include Haemophilus influenzae, Legionella pneumophila, and Staphylococcus aureus. Other bacteria, such as Mycoplasma, are a common cause of mild pneumonia but can occasionally cause serious disease.

Viruses are estimated to be the cause of adult CAP in at least 20 percent of cases. Influenza is a common viral cause of pneumonia. More recently, rhinoviruses that cause the common cold have also been shown to cause pneumonia. Other viruses that cause pneumonia in adults are human metapneumovirus, respiratory syncytial virus, parainfluenza virus, coronavirus, and adenovirus. Fungi rarely cause pneumonia in people who are generally healthy; people with a weakened immune system (those with HIV, organ transplant patients, or those on chemotherapy) are at higher risk of fungal infection.

Let your doctor know if you have traveled recently or if you been to or lived in an area where a certain type of pneumonia is more common (eg, Valley fever or coccidioidomycosis in the southwestern United States; Middle East respiratory syndrome in the Arabian Peninsula; H7N9 strain of avian influenza in Asia). The risk of pneumonia caused by new microbes (so-called "emerging pathogens") changes over time, but your doctor will know if any of the places that you have been to or lived in put you at increased risk for pneumonia.


Common symptoms of pneumonia include fever, chills, shortness of breath, pain with breathing (pleurisy), a rapid heart and breathing rate, nausea, vomiting, diarrhea, and a cough that often produces green or yellow sputum; occasionally the sputum is rust colored. Most people have a fever (temperature greater than 100.5ºF or 38ºC), although older adults have fever less often. Shaking chills (called rigors) and a change in mental status (confusion, unclear thinking) can also occur.

The characteristic symptoms of pneumonia are different from those of a more common infection, acute viral bronchitis, which does not usually cause fever and does not require treatment with an antibiotic. (See "Patient education: Acute bronchitis in adults (Beyond the Basics)".)


Pneumonia is usually diagnosed with a medical history and physical examination as well as a chest x-ray. The need for further testing depends upon the severity of the illness and the person's risk of complications.

Chest x-ray — A chest x-ray or sometimes another imaging study, such as a computed tomography (CT) scan, is used for diagnosing pneumonia when the history and physical examination also support the diagnosis.

Sputum testing — Sputum testing requires a sample of sputum collected from a deep cough. Culture of sputum is used to identify the microorganism that caused the pneumonia and can help determine which antibiotic is best.

Urine antigen testing — Urine tests can be helpful for diagnosing pneumonia caused by two bacteria, Streptococcus pneumoniae and Legionella pneumophila. These tests are easy to perform and provide rapid results.

Blood testing — Patients who are hospitalized require blood testing, including a complete blood cell count (CBC) and often a blood culture. A CBC measures the number of many types of blood cells, including white blood cells (WBC); these cells increase in number when there is a bacterial infection. An increased number of WBCs is one indicator that a bacterial infection, including pneumonia, may be present.

A blood culture is used to determine whether the infection has spread from the lungs into the blood stream. It involves taking a sample of blood from a vein and testing it for bacteria. Normally, there should be no bacteria in the bloodstream. Blood cultures are used to identify the bacteria that caused the pneumonia and to guide the choice of antibiotic. A patient's antibiotics may be changed when results of the blood or sputum cultures are completed (usually after 48 to 72 hours).

Blood oxygen measurement — Pneumonia can decrease the amount of oxygen available in the blood. As a result, a blood oxygen level is often measured by attaching a small clip to the finger or ear that uses infrared light. In those who are sicker, the oxygen level may be measured by withdrawing a sample of blood from an artery.

Bronchoscopy — Patients who present initially with severe pneumonia or who fail to improve or worsen during their hospitalization despite treatment with antibiotics may require further testing with bronchoscopy. In this procedure, a physician uses a thin, flexible tube with a camera to view the trachea and bronchi (the tube between the trachea and lungs). This allows them to look directly at the lungs, collect fluid samples or a biopsy (a small tissue sample), and determine whether there is an underlying cause of infection, such as a growth or inhaled foreign body. (See "Patient education: Flexible bronchoscopy (Beyond the Basics)".)


The goal of treatment for patients with CAP is to treat the infection and prevent complications. Initial treatment of CAP with antibiotics is based upon the organism that is likely to be causing pneumonia (called empiric treatment). Most patients improve with empiric treatment.

Hospital versus home care — Most patients are treated for CAP at home with oral antibiotics. People who are seriously ill or are at increased risk for complications may be hospitalized. Hospital monitoring usually includes measurement of heart rate and breathing rate, temperature, and oxygen levels. Hospitalized patients are usually given intravenous (IV) antibiotics initially. When they start improving, they can usually be switched to antibiotic pills.

Some patients need extra oxygen (given through small nasal tubes or a face mask) to help them breathe more easily. Patients who are still having a hard time breathing may need a breathing tube connected to a machine called a "ventilator." Some patients who need to stay in the hospital are also given steroids to help reduce inflammation in the lungs. This medicine is not the same as the steroids athletes take to build up muscle.

The number of days spent in the hospital is variable and depends upon how a person responds to treatment and if there are underlying medical problems. Some patients, including people with previous lung damage or disease, a weakened immune system, or infection in more than one lobe of the lungs (called multilobar pneumonia), may be slow to recover and require a longer hospitalization.

Antibiotic choice — A number of antibiotic treatment regimens exist for treatment of CAP. The choice of which antibiotic to use is based upon several factors, including the person's underlying medical problems and the likelihood of being infected with a bacterium that is resistant to specific drugs.

People with certain underlying medical problems and those who have used antibiotics in the past three months have a higher risk of infection with drug-resistant bacteria. For all antibiotic regimens, it is important to finish the entire course of medication and take it exactly as directed.


A person with pneumonia usually begins to improve after three to five days of antibiotic treatment. Improvement may be defined as feeling better or having fewer symptoms, such as cough and fever. Fatigue and a persistent but milder cough can last for one month or longer, although most people are able to resume their usual activities within a week. Patients treated in the hospital may not be able to resume their normal activities for three weeks or longer.

All patients, whether treated at home or in the hospital, should take special care of themselves during the recovery period. This includes getting adequate rest at night and taking naps during the day if needed. It’s important to drink plenty of fluids to avoid becoming dehydrated; there is no specific amount recommended, but thirst is a good indicator of the need to drink more fluids. Be sure to finish all of your antibiotic medication, even if you feel better after a few days.

All patients who are treated at home should have a follow-up visit or communication with a healthcare provider within several days after being diagnosed. This allows the provider to observe whether the person is improving and to check for any complications of pneumonia. Patients who have been discharged from the hospital with a pneumonia diagnosis should have a follow-up visit, usually within one week. In addition, a later visit is often recommended to confirm that the pneumonia has resolved, both in patients who were treated at home and those who were treated in the hospital.

If your symptoms do not improve or get worse after you’ve started treatment, let your healthcare provider know.


Pneumonia can usually be treated successfully without leading to complications. However, complications can develop in some patients, especially those in high-risk groups. These complications can be related to the pneumonia or to the drugs used to treat the pneumonia. In addition, pneumonia may result in worsening of chronic conditions such as chronic obstructive pulmonary disease (emphysema) or congestive heart failure.

Complications due to the pneumonia include:

Fluid accumulation – Fluid can develop between the covering of the lungs (pleura) and the inner lining of the chest wall; this is called a pleural effusion. If the fluid becomes infected as a result of pneumonia (called empyema), a chest tube (or, less commonly, surgery) may be needed to drain the fluid.

Abscess – A collection of pus in the area infected with pneumonia is known as an abscess. They can usually be treated with antibiotics; rarely, surgical removal is needed.

Bacteremia – Bacteremia occurs when the pneumonia infection spreads from the lungs to the bloodstream. This is a serious complication since infection can spread quickly from the bloodstream to other organs. Bacteremia can also cause the blood pressure to be dangerously low.

Death – Although most people recover from pneumonia, it can be fatal in some cases. The 30-day mortality rate is approximately 5 to 10 percent among patients admitted to a general medical ward but is as high as 30 percent in patients with severe infection requiring admission to an intensive care unit.

Cardiovascular events – Some studies have shown that patients who have had pneumonia are at increased risk of having a cardiovascular event, such as a heart attack during recovery from the pneumonia, and the risk persists for several years after the episode of pneumonia.

Complications due to medications used to treat the pneumonia include:

Diarrhea and rash – Each medication has a list of side effects, and patients should be familiar with the side effects of the medications used to treat their pneumonia.


Anyone who suspects that they have pneumonia should seek medical care as soon as possible. Pneumonia is a serious illness that can be life threatening if not treated, especially for people who are older than 65 years, alcoholic, have underlying medical problems, or have a weakened immune system.

People with the following symptoms should see their healthcare provider promptly:

Fever and cough with phlegm that does not improve or worsens

New shortness of breath with normal daily activities

Chest pain with breathing

Feeling suddenly worse after a cold or the flu

Respiratory symptoms (as listed above) with new confusion


The pneumococcal vaccine is one of the most effective ways to prevent pneumonia. The influenza (or "flu") vaccine is important not only for preventing influenza but also for preventing its complications, including pneumonia. These vaccines are discussed separately. (See "Patient education: Pneumonia prevention in adults (Beyond the Basics)" and "Patient education: Influenza prevention (Beyond the Basics)".)

Smoking cessation is another important way to prevent pneumonia.

Control of underlying conditions such as asthma, congestive heart failure, and diabetes can help to prevent pneumonia.

Infection control — Infection control measures can help to prevent the spread of any type of infection, including pneumonia. Infection control is most commonly practiced in healthcare settings but is useful in the community as well. Simple practices such as frequent hand washing with soap and water or alcohol-based hand rubs can be effective.

Because pneumonia is spread by contact with infected respiratory secretions, people with pneumonia should limit face-to-face contact with uninfected family and friends. The mouth and nose should be covered while coughing or sneezing, and tissues should be disposed of immediately. Sneezing/coughing into the sleeve of one's clothing (at the inner elbow) is another means of containing sprays of saliva and secretions and has the advantage of not contaminating the hands.


Your healthcare provider is the best source of information for questions and concerns related to your medical problem.

This article will be updated as needed on our web site (www.uptodate.com/patients). Related topics for patients, as well as selected articles written for healthcare professionals, are also available. Some of the most relevant are listed below.

Patient level information — UpToDate offers two types of patient education materials.

The Basics — The Basics patient education pieces answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials.

Patient education: Pneumonia in adults (The Basics)
Patient education: Community-acquired pneumonia in adults (The Basics)
Patient education: Hospital-acquired pneumonia (The Basics)
Patient education: Aspiration pneumonia (The Basics)
Patient education: Pneumocystis pneumonia (PCP) (The Basics)
Patient education: Shortness of breath (dyspnea) (The Basics)
Patient education: Cough in adults (The Basics)
Patient education: Adult respiratory distress syndrome (The Basics)
Patient education: Pleuritic chest pain (The Basics)
Patient education: Paraplegia and quadriplegia (The Basics)
Patient education: Rib fractures in adults (The Basics)
Patient education: Diabetes and infections (The Basics)
Patient education: Interstitial lung disease (The Basics)

Beyond the Basics — Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are best for patients who want in-depth information and are comfortable with some medical jargon.

Patient education: Acute bronchitis in adults (Beyond the Basics)
Patient education: Flexible bronchoscopy (Beyond the Basics)
Patient education: Pneumonia prevention in adults (Beyond the Basics)

Professional level information — Professional level articles are designed to keep doctors and other health professionals up-to-date on the latest medical findings. These articles are thorough, long, and complex, and they contain multiple references to the research on which they are based. Professional level articles are best for people who are comfortable with a lot of medical terminology and who want to read the same materials their doctors are reading.

Aspiration pneumonia in adults
Bacterial pulmonary infections in HIV-infected patients
Clinical manifestations and diagnosis of Legionella infection
Clinical presentation and diagnosis of Pneumocystis pulmonary infection in HIV-infected patients
Clinical presentation and diagnostic evaluation of ventilator-associated pneumonia
Community-acquired pneumonia in adults: Assessing severity and determining the appropriate site of care
Diagnostic approach to community-acquired pneumonia in adults
Epidemiology and pathogenesis of Legionella infection
Epidemiology, pathogenesis, and microbiology of community-acquired pneumonia in adults
Epidemiology, pathogenesis, microbiology, and diagnosis of hospital-acquired and ventilator-associated pneumonia in adults
Mycoplasma pneumoniae infection in adults
Nonresolving pneumonia
Pneumococcal pneumonia in adults
Pneumonia caused by Chlamydia pneumoniae in adults
Pseudomonas aeruginosa pneumonia
Risk factors and prevention of hospital-acquired and ventilator-associated pneumonia in adults
Sputum cultures for the evaluation of bacterial pneumonia
Treatment of community-acquired pneumonia in adults in the outpatient setting
Treatment of community-acquired pneumonia in adults who require hospitalization
Treatment of hospital-acquired and ventilator-associated pneumonia in adults
Principles of antimicrobial therapy of Pseudomonas aeruginosa infections

The following organizations also provide reliable health information.

National Library of Medicine

     (www.nlm.nih.gov/medlineplus/ency/article/000145.htm, available in Spanish)

National Institute of Allergy and Infectious Diseases


American Lung Association

     (www.lungusa.org, click on "Diseases A to Z", then click on "P")

Canadian Lung Association



Literature review current through: Oct 2017. | This topic last updated: Mon Jun 26 00:00:00 GMT+00:00 2017.
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