What Is Pneumonia?

Pneumonia is a common lung infection caused by bacterial, viral, and fungal infections. With pneumonia, the air sacs fill with fluid or pus and can cause mild to life-threatening symptoms such as shortness of breath, cough, fever, chest pain, and fatigue. Pneumonia is diagnosed through a physical exam and lab and imaging tests. Treatment varies, depending on the cause and severity of symptoms. 

Pneumonia can occur at any age, but children, older adults, and people with weakened immune systems are most vulnerable. In the United States, over 120 million children under age 5 are diagnosed with pneumonia, and about 1.5 million adults seek medical care at a hospital due to pneumonia every year.


There are several different types of pneumonia, which are classified based on the pathogen (germ) that caused the infection.

  • Bacterial: Various bacteria species can cause pneumonia; Streptococcus pneumoniae is the most common pneumonia-associated bacteria in the U.S.
  • Viral: Viruses that affect the respiratory tract, such as influenza or respiratory syncytial virus (RSV), can lead to pneumonia.
  • Fungal: Fungi, such as pneumocystis pneumonia (PCP), can cause pneumonia in people with chronic health conditions and weakened immune systems.
  • Walking: A form of pneumonia caused by the Mycoplasma pneumoniae bacteria that is usually mild enough that you can continue your day-to-day activities. 
  • Aspiration: Occurs when mouth secretions, stomach contents, or food are inhaled into the lungs rather than swallowed.

Healthcare providers also type pneumonia based on where the infection was acquired:

  • Community-acquired pneumonia: Develops outside of a hospital or healthcare setting, usually due to a bacterial, viral, or fungal infection.
  • Hospital-acquired pneumonia: Develops during hospitalization and can be more serious than other lung infections because germs commonly found in hospital settings are often more treatment-resistant. 

Pneumonia Symptoms 

Pneumonia symptoms range in severity from mild to life-threatening. Young children, older adults, and immunocompromised people have a higher risk of developing more serious symptoms and complications.

Common pneumonia symptoms can include:

Less common pneumonia symptoms may include: 

  • Headache 
  • Muscle aches and pains 
  • Extreme fatigue 
  • Nausea
  • Vomiting 
  • Diarrhea 

Some older adults and people with weakened immune systems may have atypical symptoms, such as a low body temperature rather than a fever. Many older adults may have sudden changes in mental awareness and become confused. 

Infants and young children may have additional pneumonia symptoms, such as: 

  • Bluish-colored skin and lips 
  • Rapid breathing
  • Grunting 
  • Widened nostrils and inward pulling of rib muscles when breathing
  • Irritability or fussiness 

What Causes Pneumonia?  

Pneumonia is usually caused by pathogens such as bacteria, viruses, and fungi. It can also occur when liquid or food is aspirated (inhaled) rather than swallowed. As the body’s immune system fights the germs, the lungs become inflamed, causing the tiny air sacs (alveoli) to fill with fluid or pus.

Many types of bacteria can cause pneumonia, with Streptococcus pneumoniae being the most common bacteria associated with pneumonia in the United States. Viruses that affect your respiratory tract, such as influenza, respiratory syncytial virus (RSV), or the common cold, are the most common cause of viral pneumonia. Fungi, such as Pneumocystis jirovecii, can cause pneumonia, especially in immunocompromised people. 

Risk Factors

Pneumonia can affect anyone, but certain risk factors can increase your chances of developing it:

  • Age: Infants and children ages two and younger and older adults (65 and older) are more vulnerable to pneumonia. 
  • Environment: The risk of pneumonia is higher for those who work or live in crowded places, such as homeless shelters, prisons, nursing homes, or dorms. 
  • Occupation: People exposed to chemical fumes and dust and those who work in an environment involving animal exposure (e.g., meat processing center, veterinary clinic) are at a higher risk.  
  • Weakened immune system: Immunocompromised people, such as those with HIV/AIDS or undergoing chemotherapy, are more likely to develop pneumonia. 
  • Hospitalization: Getting medical care in a hospital can raise the risk of hospital-acquired pneumonia, especially if you are sedated or unconscious and unable to move around or require a ventilator to help you breathe. 
  • Smoking: Over time, smoking damages the lungs, increasing your risk of pneumonia. 
  • Other medical conditions: Lung diseases and medical conditions that affect your ability to cough or swallow can increase your pneumonia risk. 


Pneumonia can be challenging to diagnose because the symptoms resemble those caused by influenza or the common cold. A healthcare provider will ask about your medical history and symptoms to diagnose pneumonia. They may ask about recent travel, exposure to sick people and animals, and whether you’ve recently had an illness. 

During the physical exam, your healthcare provider will look for signs and symptoms of pneumonia and use a stethoscope to listen for crackling, popping, or rumbling sounds in your lungs when you breathe.

Diagnostic tests may be ordered to confirm a pneumonia diagnosis, such as:

  • Chest X-ray: Takes pictures of the lungs to look for signs of inflammation or fluid buildup in and around your lungs.
  • Blood tests: To confirm an infection and determine the type of germ-causing pneumonia.
  • Pulse oximetry: Measures the oxygen level in your blood, which may be lower with pneumonia.
  • Sputum culture: A sample of mucus from the lungs is collected when you cough and analyzed in a laboratory to identify the pathogen causing your pneumonia. 

Additional diagnostic tests may be ordered if you are at high risk for pneumonia complications or are hospitalized. These include: 

  • Computerized tomography (CT) scan: Provides detailed images of the lungs and surrounding structures to look for pus-filled spots (abscesses) and other complications.
  • Bronchoscopy: A thin, flexible tube is passed through the nose or mouth to collect a sample of lung tissue (biopsy) or fluid for analysis. 
  • Arterial blood gas: Measures the amount of oxygen in blood taken from an artery, which provides more accurate results than pulse oximetry. 
  • Pleural fluid culture: A small amount of fluid is removed from tissues surrounding the lungs and sent to the lab to identify the pathogen causing pneumonia. 

Treatments for Pneumonia  

The goal of treatment for pneumonia is to relieve symptoms, cure the infection, and prevent complications. Treatment approaches vary, depending on what’s causing pneumonia, the severity of your symptoms, and your overall health. 


The type of medication prescribed to treat pneumonia depends on whether bacteria, a virus, or a fungus caused the infection.

  • Antibiotics are prescribed to treat bacterial pneumonia. You should feel better within a few days of antibiotic treatment. You must take the full course to eliminate the infection. If you stop taking antibiotics too soon, the infection could return and be harder to treat. 
  • Antiviral medicines are often prescribed to treat viral pneumonia. These medicines don’t work for every virus, so rest and symptom management may be all you need for your body to fight off the infection.
  • Antifungal medicines are prescribed to treat fungal pneumonia. 
  • Over-the-counter pain relievers such as Tylenol (acetaminophen) and Advil (ibuprofen) can help relieve pain and discomfort and reduce your fever. 

At-Home Management 

Most people with pneumonia can safely manage symptoms and recover at home. If you have a mild case of pneumonia, a healthcare provider may prescribe medication and recommend the following:

  • Get lots of rest to give your body a chance to recover and recuperate 
  • Drink plenty of fluids to help break up mucus in your lungs 
  • Drink warm beverages, take hot showers or baths, and use a humidifier to keep your airways open
  • Avoid exposure to lung irritants, such as cigarette smoke, chemicals, wood smoke, and allergens (e.g., pollen, dust) while your lungs heal 


If your infection is serious or you develop complications of pneumonia (e.g., lung abscess) you may be hospitalized for treatment. Hospital treatments for severe pneumonia can include:

  • Oxygen therapy: Helps increase oxygen levels in your blood if you have trouble breathing. 
  • IV fluids and medicines: Medications (e.g., antibiotics) and fluids may be administered intravenously (IV).
  • Mechanical ventilation: If you are having trouble breathing, you may require a ventilator to help you breathe.
  • Surgery: If part of your lung is seriously infected or damaged, you may need surgery to remove the damaged parts and prevent pneumonia from returning. 

How to Prevent Pneumonia

Healthy lifestyle choices can lower your risk of infection and help prevent pneumonia. Here’s how:

  • Get vaccinated: Vaccines that protect against the most common causes of pneumonia, such as influenza, COVID-19, and pneumococcus bacteria, can help prevent certain types of pneumonia and lower your risk of complications. 
  • Good hygiene: Wash your hands frequently with soap and water to kill germs and avoid touching your face in public spaces. 
  • Don't smoke: Smoking damages the lungs and weakens the immune system, making it harder to fight off infections. 
  • Stay healthy: Eat a balanced, nutritious diet, exercise regularly, and get enough sleep to help keep your immune system strong. 
  • Manage chronic conditions: If you have a chronic condition such as heart disease, diabetes, or COPD, follow your treatment plan to manage the condition. 

Comorbid Conditions   

People with certain health conditions are at a greater risk of developing pneumonia and experiencing complications. Common comorbid conditions associated with a higher risk of pneumonia include:

  • Obesity
  • Diabetes
  • High blood pressure
  • Cardiovascular disease 
  • Chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema 
  • Alcohol use disorder 
  • Malnutrition 

Living With Pneumonia  

If you have symptoms of pneumonia, see a healthcare provider. Getting an early diagnosis and starting treatment can help prevent complications and help you feel better sooner. Along with following your treatment plan, resting and staying hydrated are important to your recovery. Most people recover within 1-2 weeks, but it may be several weeks before your energy levels return to normal.

Visit your healthcare provider for follow-up care, especially if your symptoms are not improving. They may suggest additional treatments or therapies, such as physical therapy to regain strength or pulmonary rehabilitation to help your lungs recover. Making lifestyle changes, such as quitting smoking, staying up-to-date on vaccinations, and managing chronic conditions, can help reduce the risk of future infections and improve your overall health. 

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15 Sources
Health.com uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Thoracic Society. Top 20 pneumonia facts - 2019.

  2. MedlinePlus. Pneumonia.

  3. Merck Manual: Consumer Version. Aspiration pneumonia and chemical pneumonitis

  4. Lanks CW, Musani AI, Hsia DW. Community-acquired pneumonia and hospital-acquired pneumonia. Med Clin North Am. 2019;103(3):487-501. doi:10.1016/j.mcna.2018.12.008

  5. National Heart, Lung and Blood Institute. Pneumonia symptoms.

  6. American Lung Association. Pneumonia symptoms and diagnosis.

  7. American Lung Association. What causes pneumonia?.

  8. National Heart, Lung and Blood Institute. Pneumonia causes and risk factors.

  9. American Lung Association is important. Pneumonia symptoms and diagnosis.

  10. American Lung Association. Pneumonia treatment and recovery.

  11. National Heart, Lung and Blood Institute. Pneumonia treatment.

  12. National Heart, Lung and Blood Instiute. Pneumonia prevention.

  13. Rivero-Calle I, Cebey-López M, Pardo-Seco J, et al. Lifestyle and comorbid conditions as risk factors for community-acquired pneumonia in outpatient adults (NEUMO-ES-RISK project). BMJ Open Respir Res. 2019;6(1):e000359. doi:10.1136/bmjresp-2018-000359

  14. Vidal A, Santos L. Comorbidities impact on the prognosis of severe acute community-acquired pneumonia. Porto Biomed J. 2017;2(6):265-272. doi:10.1016/j.pbj.2017.04.009

  15. National Heart, Lung and Blood Institute. Pneumonia recovery.

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