Pneumonia can be the result of numerous types of bacteria, viruses and fungi. Pneumonia rarely affects healthy adults but is a frequent complication of hospitalization or other illnesses.

Pneumonia Overview

Reviewed: May 9, 2014

Pneumonia is an infection in one or both of the lungs caused by bacteria, viruses, and less frequently, fungi.

The infection causes inflammation in the alveoli, the air sacs of the lungs. The air sacs may fill up with fluid or pus, causing symptoms such as a cough with phlegm, fever, chills, and trouble breathing. Pneumonia causes cough, fever and difficulty breathing. Sometimes patients can receive treatments and get better at home, while others may require hospitalization, especially the very young or elderly.

The signs and symptoms of pneumonia vary from mild to severe. Many factors affect how serious pneumonia is, including the type of germ causing the infection and your age and overall health. Common symptoms include a high fever, shaking chills, cough with phlegm (a slimy substance), which doesn't improve or worsens, shortness of breath with normal daily activities, chest pain with breathing or coughing, and feeling suddenly worse after a cold or the flu.

Bacterial pneumonia is treated with antibiotics. Acetaminophen may be used to treat fevers. Severe pneumonia may require hospitalization and treatment with oxygen therapy and IV antibiotics.

Pneumonia Symptoms

The signs and symptoms of pneumonia vary from mild to severe. Many factors affect how serious pneumonia is, including the type of germ causing the infection and your age and overall health. See your doctor promptly if you:

  • Have a high fever
  • Have shaking chills
  • Have a cough with phlegm (a slimy substance), which doesn't improve or worsens
  • Develop shortness of breath with normal daily activities
  • Have chest pain when you breathe or cough
  • Feel suddenly worse after a cold or the flu

People who have pneumonia may have other symptoms, including nausea (feeling sick to the stomach), vomiting, and diarrhea.

Symptoms may vary in certain populations. Newborns and infants may not show any signs of the infection. Or, they may vomit, have a fever and cough, or appear restless, sick, or tired and without energy.

Older adults and people who have serious illnesses or weak immune systems may have fewer and milder symptoms. They may even have a lower than normal temperature. If they already have a lung disease, it may get worse. Older adults who have pneumonia sometimes have sudden changes in mental awareness.

Pneumonia Causes

Bacteria, viruses, and less often, fungi, can cause pneumonia. When the immune system tries to attack the germs the air sacs in the lungs fill up with fluid and pus, causing the symptoms of pneumonia.

Bacterial pneumonia is the most common type of pneumonia in adults. There are many types of bacteria that can cause pneumonia, however, the most common bacteria to cause pneumonia in the U.S. is Streptococcus pneumoniae.

Viral pneumonia is more common in children younger than 5 years of age. Respiratory viruses cause up to one-third of the pneumonia cases in the United States each year. 

The flu virus is the most common cause of viral pneumonia in adults. Other viruses that cause pneumonia include respiratory syncytial virus, rhinovirus, herpes simplex virus, severe acute respiratory syndrome (SARS), and more.

Three types of fungi in the soil in some parts of the United States can cause pneumonia. These fungi are:

  • Coccidioidomycosis: This fungus is found in Southern California and the desert Southwest.
  • Histoplasmosis: This fungus is found in the Ohio and Mississippi River Valleys.
  • Cryptococcus: This fungus is found throughout the United States in bird droppings and soil contaminated with bird droppings.

Most people exposed to these fungi don't get sick, but some do and require treatment.

Other kinds of fungal infections also can lead to pneumonia.

You are more likely to get pneumonia if:

  • Your immune system is weak
  • A germ is very strong
  • Your body fails to filter germs out of the air that you breathe

Types of Pneumonia

  • Community-acquired pneumonia (CAP) is the most common type of pneumonia, which usually occurs during the winter. About 4 million people get this form of pneumonia each year, 20 percent of which require hospital treatment.
  • Just as the name implies, hospital-acquired pneumonia (HAP) is a type of pneumonia people catch during a hospital stay for another illness. You're at higher risk of getting this more serious form of pneumonia if you're on a ventilator (a machine that helps you breathe).
  • Health care-associated pneumonia occurs when patients get pneumonia while in nursing homes or outpatient medical settings.
  • When food, beverages, vomit or saliva are inhaled from the mouth into the lungs, aspiration pneumonia may occur. This is more common in people with brain injury, abnormal gag reflex, difficulty swallowing, or in people who abuse alcohol or drugs. Sometimes pus forms in the cavity of the lung. This is known as a lung abscess.
  • Several types of bacteria—Legionella pneumophila, mycoplasma pneumonia, and Chlamydophila pneumoniae—cause atypical pneumonia, a type of CAP. Atypical pneumonia is passed from person to person.


Pneumonia Diagnosis

In order to diagnose pneumonia, your health care provider may require a medical history, a physical exam, and certain laboratory tests.

During the physical exam your health care provider will listen to your lungs with a stethoscope to check for abnormal cracking, bubbling or rumbling sounds, or wheezing during inhalation. These sounds indicate the presence of thick liquid, which may point to pneumonia.

A chest x ray is the best test for diagnosing pneumonia. However, this test won't tell your health care provider what kind of germ is causing the pneumonia. A computed tomography (CT) scan can also show the lungs in detail.

A complete blood count (CBC) can be used to measure, among other things, the number of white blood cells in the blood sample, which can indicate a bacterial infection.

To determine which germ is causing the infection, a blood culture or sputum test may be performed.


Living With Pneumonia

Follow your health care provider's treatment plan and get plenty of rest. Take the full course of antibiotics prescribed, even if you are feeling well. Do not stop taking antibiotics without the advice of your health care provider.

Although you will begin to feel well and symptoms may ease within a few days, the associated fatigue may last for weeks.

Attend all of your medical appointments as scheduled. Your health care provider may recommend a follow-up chest x-ray.

Resume normal activities as directed by your health care provider.

Pneumonia Treatments

Treatment will depend on the type and severity of your pneumonia.

  • Bacterial pneumonia is treated with medicines called antibiotics.
  • For fevers, aspirin, ibuprofen, and acetaminophen may be recommended.
  • Cough medications may be prescribed if you are having difficulty sleeping. 
  • For viral pneumonia, your health care provider may prescribe an antiviral medicine to treat it. Antibiotics won't work.

You may need to be treated in a hospital if:

  • Your symptoms are severe
  • You're at risk for complications because of other health problems
  • Oxygen therapy and IV antibiotics may be used in hospital


Pneumonia Prognosis

It may take time to recover from pneumonia. Some people feel better and are able to return to their normal routines within a week. For other people, it can take a month or more. Most people continue to feel tired for about a month. Talk with your doctor about when you can go back to your normal routine.