Learn About Pneumonia

What is the definition of Pneumonia?

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


This article covers community-acquired pneumonia (CAP). This type of pneumonia is found in people who have not recently been in the hospital or another health care facility such as a nursing home or rehab facility. Pneumonia that affects people in health care facilities, such as hospitals, is called hospital-acquired pneumonia (or health care-associated pneumonia).

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What are the alternative names for Pneumonia?

Bronchopneumonia; Community-acquired pneumonia; CAP

What are the causes of Pneumonia?

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. In adults, bacteria are the most common cause of 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).
Respiratory system

Pneumonia can be caused by many types of germs.

  • The most common type of bacteria is Streptococcus pneumoniae (pneumococcus).
  • Atypical pneumonia, often called walking pneumonia, is caused by other bacteria.
  • A fungus called Pneumocystis jirovecii can cause pneumonia in people whose immune system is not working well, especially people with advanced HIV infection.
  • Viruses, such as the flu virus, and most recently SARS-CoV-2 (which causes COVID-19), are also common causes of pneumonia.

Risk factors that increase your chance 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, organ transplant, or other diseases)
  • Other serious illnesses, such as heart disease, liver cirrhosis, or diabetes
  • Recent surgery or trauma
  • Surgery to treat cancer of the mouth, throat, or neck
What are the symptoms of Pneumonia?

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 or exert yourself)

Other symptoms include:

  • Confusion, especially in older people
  • Excess sweating and clammy skin
  • Headache
  • Loss of appetite, low energy, and fatigue
  • Malaise (not feeling well)
  • Sharp or stabbing chest pain that gets worse when you breathe deeply or cough
  • White nail syndrome, or leukonychia
White nail syndrome
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What are the current treatments for Pneumonia?

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

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

If you are diagnosed with a bacterial form of pneumonia, it is important that you are started on antibiotics very soon after you are admitted. If you have viral pneumonia, you will not receive antibiotics. This is because antibiotics do not kill viruses. You may receive other medicines, such as antivirals, if you have the flu.

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
  • Have been taking antibiotics at home and are not getting better

Many people can be treated at home. If so, your provider may tell you to take medicines such as antibiotics.

When taking antibiotics:

  • Do not miss any doses. Take the medicine until it is gone, even when you start to feel better.
  • Do not take cough medicine or cold medicine unless your doctor says it is OK. 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 2 or 3 times every hour. Deep breaths will help open up your lungs.
  • Tap your chest gently a few times a day while lying with your head lower than your chest. This helps bring up mucus from the lungs so that you can cough it out.

Drink plenty of liquids, as long as your provider says it is OK.

  • Drink water, juice, or weak tea
  • Drink at least 6 to 10 cups (1.5 to 2.5 liters) 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.

Who are the top Pneumonia Local Doctors?
Highly rated in
Pulmonary Medicine
Intensive Care Medicine

Pulmonary Practice At Parnassus

400 Parnassus Ave 
San Francisco, CA 94143

Harold Collard is a Pulmonary Medicine specialist and an Intensive Care Medicine doctor in San Francisco, California. Dr. Collard has been practicing medicine for over 25 years and is rated as an Elite doctor by MediFind in the treatment of Pneumonia. He is also highly rated in 8 other conditions, according to our data. His top areas of expertise are Hypersensitivity Pneumonitis, Acute Interstitial Pneumonia, Interstitial Lung Disease, and Idiopathic Pulmonary Fibrosis. He is board certified in Pulmonary Disease, Critical Care (Intensivists), and Internal Medicine and licensed to treat patients in California.

Highly rated in
Pulmonary Medicine
Intensive Care Medicine

University of California San Francisco Health System

ILD Program

400 Parnassus Ave 
San Francisco, CA 94143

Paul Wolters is a Pulmonary Medicine specialist and an Intensive Care Medicine doctor in San Francisco, California. Dr. Wolters has been practicing medicine for over 30 years and is rated as an Elite doctor by MediFind in the treatment of Pneumonia. He is also highly rated in 10 other conditions, according to our data. His top areas of expertise are Idiopathic Pulmonary Fibrosis, Acute Interstitial Pneumonia, Hypersensitivity Pneumonitis, and Interstitial Lung Disease. He is board certified in Pulmonary Disease and Critical Care (Intensivists) and licensed to treat patients in California. Dr. Wolters is currently accepting new patients.

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Highly rated in

St James's Hospital

School Of Medicine 
Dublin, L, IE 

Ignacio Martin-Loeches is in Dublin, Ireland. Martin-Loeches is rated as an Elite expert by MediFind in the treatment of Pneumonia. He is also highly rated in 18 other conditions, according to our data. His top areas of expertise are Hospital-Acquired Pneumonia, Pneumonia, Sepsis, and Tracheitis.

What is the outlook (prognosis) for Pneumonia?

With treatment, most people improve within 2 weeks. Older adults or very sick people may need longer treatment.

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

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

In all of the above conditions, pneumonia can lead to death, if it is severe.

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

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

Your provider may order another x-ray. This is to make sure your lungs are clear. But it may take many weeks for your x-ray to clear up. You will likely feel better before the x-ray clears up.

When should I contact a medical professional for Pneumonia?

Call your provider if you have:

  • 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)
  • Worsening of symptoms after initial improvement
How do I prevent Pneumonia?

You can help prevent pneumonia by following the measures below.

Wash your hands often, especially:

  • Before preparing and eating food
  • After blowing your nose
  • After using the toilet
  • After changing a baby's diaper
  • After coming in contact with people who are sick

Avoid coming into contact with people who are sick.

Do not smoke. Tobacco damages your lung's ability to fight infection.

Vaccines may help prevent some types of pneumonia. Be sure to get the following vaccines:

  • Flu vaccine can help prevent pneumonia caused by the flu virus.
  • Pneumococcal vaccine lowers your chances of getting pneumonia from Streptococcus pneumoniae.

Vaccines are even more important for older adults and people with diabetes, asthma, emphysema, HIV, cancer, people with organ transplants, or other long-term conditions.

What are the latest Pneumonia Clinical Trials?
A 20-months Surveillance of Non-invasive Streptococcus Pneumoniae Infections in Belgium to Evaluate National Vaccination Strategy
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A Pilot Placebo-controlled Randomized Double-blind Trial of Melatonin in Outpatients With COVID-19 Infection
What are the Latest Advances for Pneumonia?
Auxora vs. placebo for the treatment of patients with severe COVID-19 pneumonia: a randomized-controlled clinical trial.
A Case of Heart Transplantation for Fulminant Myocarditis After ChAdOx1 nCoV-19 Vaccination.
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Who are the sources who wrote this article ?

Published Date : August 03, 2020
Published By : Denis Hadjiliadis, MD, MHS, Paul F. Harron Jr. Associate Professor of Medicine, Pulmonary, Allergy, and Critical Care, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. Editorial update 09/28/2021.

What are the references for this article ?

Daly JS, Ellison RT. Acute pneumonia. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 67.

Musher DM. Overview of pneumonia. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 26th ed. Philadelphia, PA: Elsevier; 2020:chap 91.

Wunderink RG. Guidelines to manage community-acquired pneumonia. Clin Chest Med. 2018;39(4):723-731. PMID: 30390744 pubmed.ncbi.nlm.nih.gov/30390744/.