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Pneumonia is an inflammatory condition of the lung, where the small air sacs, known as alveoli, fill with fluid. It is most often caused by an infection from bacteria.^[1][2]

Symptoms for pneumonia typically include, cough, fatigue, chills, and shortness of breath. Each of the symptoms occurs with different frequencies.^[3]

Symptoms

Cough and fatigue are the most common symptoms, and seen in up to 9 out of 10 cases. Fever and shortness of breath, are present in roughly 3 out of 4 people. Productive sputum is present in 65 percent of cases, and chest pain occurs in roughly one-half of people.^[4]

Elderly

In the elderly, confusion may be the most prominent sign,^[3] and fever is less likely to be present.

Children Early Symptoms

In children under the age of five, fever, cough, and fast or difficult breathing are the most common symptoms.^[5]

Children Severe Pneumonia

More severe signs and symptoms in children may include, blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.^[5][6]

Pneumonia fills the lung's alveoli with fluid, limiting how much oxygen can be absorbed. The alveolus on the left is normal, whereas the one on the right is full of fluid from pneumonia.

Bacterial Pneumonia

Pneumonia is usually caused by infection from bacteria or viruses. It is less commonly caused by other microorganisms, certain medications, and conditions, such as autoimmune diseases.^[1][7]

Risk factors

Risk factors for pneumonia, include smoking, a poor ability to cough, (such as after a stroke or surgery), and other lung diseases such as cystic fibrosis, COPD, and asthma.^[8]

Diagnosis, is often based on symptoms and physical examination alone.^[9]

Diagnosis - Other Methods

Chest X-ray, blood tests, and culture of the sputum, may help confirm the diagnosis.^[9]

Classification

Where (and how) a pneumonia was acquired, can have a profound impact on survival. Examples are community-acquired, or hospital-acquired pneumonia. ^[10]

Because most pneumonias, are acquired from someone else that is infected, handwashing, and wearing surgical masks around the sick, are the most important preventative steps^[11].

Vaccine

Vaccines to prevent certain types of pneumonia are available.^[12]

Other Methods

Other methods of prevention, include smoking cessation, and treating underlying illnesses (such as diabetes and HIV) properly.^[12]

Antibiotics by mouth, rest, and simple analgesics and fluids, are usually enough to treat uncomplicated pneumonia.^[13]

Children

In children, those with respiratory distress, or oxygen saturations of less than 90%, should be hospitalized.^[14]

Prognosis

With treatment, most types of bacterial pneumonia, will stabilize in 3–6 days.^[15] It often takes a few weeks before most symptoms resolve.^[15].

Severe pneumonia

If the pneumonia is severe, the affected person is generally hospitalized, ^[16] and oxygen therapy may be necessary.^[17]

Pneumonia is a common illness, affecting approximately 450 million people a year, and occurring in all parts of the world.^[18] It is a major cause of death among all age groups, resulting in 7% of the world's total death yearly.^[18][19]

Death rates, are greatest in children less than five, and adults older than 75 years.^[18]

In the 19th century, William Osler called pneumonia "the captain of the men of death".^[20]

Survival rates

With the introduction of antibiotics and vaccines in the 20th century, survival has improved.^[18]

Developing countries

Nevertheless, in developing countries, and among the very old, young, and chronically ill, pneumonia remains a leading cause of death.^[18][21]