Pneumonia is a lung infection caused by viral, bacterial, or fungal germs. It ranges in severity from mild to life-threatening, especially for individuals in higher-risk populations. Different types of pneumonia are categorized by how the infection was acquired or its severity.

This article provides an overview of pneumonia, including types, causes, symptoms, treatment, prevention tips, and more.

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What Is Pneumonia?

Pneumonia is a lung infection that can affect one or both lungs. It causes the air sacs in your lungs to fill with liquid or pus, making it harder to breathe. This infection can affect individuals differently, with symptoms ranging from mild to life-threatening and requiring immediate medical attention.

Types of Pneumonia

Pneumonia is commonly a result of bacteria or viruses, or rarely, it can be caused by a fungus; however, in many cases, it’s difficult for healthcare providers to determine which has caused pneumonia. Research suggests no causative germ can be identified in over 50% of cases.

Pneumonia may be described with nonmedical terms related to how it impacts someone, such as:

  • Walking pneumonia (atypical pneumonia) is a mild infection in which a patient can carry on life as usual, without lying in bed.
  • Double pneumonia is an infection in both lungs.

Pneumonia is also described by how the infection was likely acquired, including:

  • Hospital-acquired pneumonia develops 48 hours or more after admission to the hospital.
  • Ventilator-associated pneumonia occurs when a person supported by a ventilator develops pneumonia.
  • Community-acquired pneumonia describes pneumonia that develops outside of a hospital setting.

Additionally, aspiration pneumonia happens when someone inhales a foreign substance, like food or beverage, into their lungs, and it causes an infection. This is more likely to have severe effects among older adults or someone under anesthesia and unaware.

Stages of Pneumonia

Pneumonia is less likely to have severe outcomes when diagnosed and treated effectively within its earliest stage. It affects the smallest airways in your lungs, where carbon dioxide and oxygen exchange occur, making breathing more difficult as it progresses.

During the first few days of pneumonia, you may have severe symptoms even if treatment has already begun. During this time, treatment could include antibiotics and supplemental oxygen.

As the first week of infection continues, pneumonia symptoms may worsen or begin to clear up, depending on the type, severity, and treatment plan. Complications such as a lung abscess (pus-filled cavity in the lung) and worsening cough, night sweats, coughing up blood, or unintentional weight loss may occur. In this case, a healthcare provider may prescribe antibiotics. If you have a lung abscess, it may need draining or surgical intervention.

In late-stage pneumonia, which typically starts around day eight of an infection, your immune system works hard to repair damage to your lungs. As this occurs, you usually cough to help remove any remaining debris. Antibiotics are typically prescribed for at least 10 days, but you may be weaned off of supplemental oxygen. If you continue to have complications during this time, mechanical ventilation may be necessary to allow the lungs to heal.

Long-term lung damage is possible for some people, requiring continued supplemental oxygen.

What Causes Pneumonia?

Pneumonia is either caused by organisms, such as viruses, bacteria, or fungi, or by aspiration (when a foreign substance accidentally enters the lungs). It may be acquired in a community setting, a hospital setting, or from being on a mechanical ventilator.

Some of the most common pneumonia-causing organisms include:

Bacterial pneumonia is commonly caused by Streptococcus pneumonia. Kids are especially susceptible to infections caused by Mycoplasma pneumoniae.

While these are the most common germs to cause pneumonia, healthcare providers cannot always identify which one may have caused the infection and, therefore, try to treat it broadly.

The COVID-19 and Pneumonia Connection

The virus that causes COVID-19 is a common cause of viral pneumonia. One study found that over 90% of hospitalized patients with COVID-19 also tested positive for pneumonia. Those with severe COVID-19 symptoms had a 10% higher likelihood of developing pneumonia than those without symptoms.

COVID-19 pneumonia commonly affects both lungs and is more likely to have long-lasting effects, though data on this are still young.

Who Has the Highest Risk of Developing Pneumonia?

While pneumonia can vary in severity, certain populations are at a higher risk for developing pneumonia and complications, which include:

Symptoms of Pneumonia

A pneumonia infection often starts suddenly with noticeable symptoms that worsen, such as:

Bronchitis vs. Pneumonia

Bronchitis is when the small airways that distribute oxygen in your lungs (bronchioles) become inflamed and filled with mucus. This often occurs after you have a cold or other viral infection. Pneumonia affects the tiny sacs in your lungs that move oxygen and carbon dioxide in and out of your bloodstream (alveoli).

Both illnesses are spread by the transfer of fluid droplets from an infected person. They have similar symptoms, such as fever, cough, chest ache, and fatigue, but pneumonia is generally more severe.

Pneumonia Symptoms in Young Children

Babies and young children may not have typical pneumonia symptoms, so paying attention to anything out of the ordinary is important. Babies may have a cough, fever, restlessness, fatigue, or vomiting.

Because pneumonia is a respiratory infection, there may also be signs of breathing difficulty, such as rapid breathing, pulling inward of the muscles around the ribs, widening of nostrils when breathing, grunting, fussiness, or a bluish tone to the lips and skin indicating low oxygen.

Call your pediatrician or seek emergency medical care if you notice anything unusual in your child’s health and breathing pattern.

Pneumonia Symptoms in Older Adults

Older adults may initially not have typical pneumonia symptoms and instead experience confusion and falls. Some people may also experience coughing up blood or bouts of nausea, vomiting, and diarrhea. Additionally, their temperature may be lower than average versus having a fever. They may also show signs of labored breathing or complain of chest pain.

Is Pneumonia Contagious?

Pneumonia is most contagious when caused by a bacterium or virus, as these can be easily transferred to others through the air or shared surfaces. Aspiration or fungal pneumonia may not always be contagious.

Still, pneumonia should be treated as a contagious respiratory infection, mainly because it can be challenging to determine what type of germ it is caused by.

When to Seek Emergency Care for Pneumonia

Pneumonia can become severe quickly if left untreated, especially for people in high-risk populations. Seek emergency medical care if you experience difficulty breathing, are coughing up blood or pus, or have a high fever, chest pain, or a consistent cough.

People over age 65, infants and young children, and people with preexisting medical conditions should see a healthcare provider for pneumonia treatment since they are at a higher risk for complications.

Diagnosing Pneumonia

In addition to reviewing your symptoms, a healthcare provider will use one or more diagnostic tests to confirm pneumonia. These could include:

  • Blood test: Used to identify the specific germ that caused the pneumonia infection
  • Chest X-ray: Used to visualize how the infection is affecting your lungs
  • Pulse oximetry: Used to measure the amount of oxygen in your blood, since pneumonia can affect your breathing
  • Sputum test: Used to examine mucus and identify the underlying cause of pneumonia

Once a pneumonia diagnosis is made, a healthcare provider can determine the best way to treat your infection.

How Is Pneumonia Treated?

Pneumonia treatment depends on the infection’s severity but generally involves medication and home remedies.


Pneumonia is treated using antibiotics. Broad-spectrum antibiotics may be used until the results of antibiotics sensitivity testing are available, which allows for more targeted antibiotic treatment.

Home Remedies

In addition to medicine, pneumonia treatment involves rest, drinking plenty of fluids, not smoking and avoiding secondhand smoke, and staying away from others to prevent transmission while contagious. You might also use fever-reducing medications and steamy showers or humidifiers.

Can Pneumonia Go Away on Its Own?

While mild cases of pneumonia may eventually go away on their own as your immune system works, untreated pneumonia can lead to severe complications that may even become life-threatening for some people. Speak with a healthcare provider regarding symptoms, especially if you’re having trouble breathing or have high fevers, to determine the best treatment plan.

Signs That Pneumonia Is Improving

As pneumonia improves, your symptoms will begin to subside. Fevers will go away with normalized temperatures, you will produce less mucus, your chest will feel better, your cough will resolve, it will become easier to breathe, and your fatigue will improve. How long it takes for pneumonia symptoms to resolve depends on the individual, the severity of the infection, and your course of treatment.

Complications of Pneumonia

Left untreated, pneumonia complications are more likely to occur. Below are some of the most common complications of pneumonia, which generally need to be diagnosed using chest imaging:

  • Lung abscess: This pus-filled cavity forms when lung tissue dies. When multiple abscesses are present, this is called necrotizing pneumonia.
  • Bacteremia: Bacteremia is when bacteria are circulating in the blood; it’s the most common cause of sepsis and includes body-wide organ failure.
  • Respiratory failure: This occurs when your lungs cannot get enough oxygen into your blood. The lung infections can promote inflammation and damage that reduces oxygen transport, leads to carbon dioxide buildup, and damages organs and tissues.
  • Collapsed lung: Also called pneumothorax, this is a rare complication of pneumonia in which air escapes outside of the lung and into the pleural cavity, making it difficult to breathe.
  • Pleural effusion: This is when fluid builds up between the chest wall and the lungs. When caused by pneumonia, it may also lead to empyema, which is the buildup of pus in this area.
  • Kidney failure: Pneumonia bacteria can get into the bloodstream and infect your kidneys, especially if there is a lack of oxygen due to respiratory failure or bacteremia. People with existing kidney disease can be more susceptible to pneumonia infections and complications.

The best way to avoid complications of pneumonia is to seek medical attention for any concerning symptoms and follow your healthcare provider’s prescribed treatment plan.

How to Prevent Pneumonia

The best ways to prevent pneumonia are by practicing health hygiene, boosting your natural immunity, getting a pneumonia vaccine, and avoiding people who are ill. Furthermore, if you’re feeling sick, you can always speak to your healthcare provider about your symptoms and see whether they suspect pneumonia so it can be treated in a timely manner.


There are two types of pneumonia vaccines that can help reduce your risk of having severe pneumonia and complications:

  • Pneumococcal conjugate vaccines (PCV13 and PCV15): PCV13 and PCV15 are recommended for children under age 5 and may be given to babies as a standard vaccination series. They can also be given to adults over 65 as a onetime vaccine.
  • Pneumococcal polysaccharide vaccine (PPSV23): This protects against 23 kinds of bacteria that cause pneumonia. PPSV23 can be given to adults and children aged 2 to 18 with medical conditions that increase their risk of pneumococcal disease. PPSV23 is also recommended for children between 2 and 8 years old with medical conditions that increase their risk for pneumonia.

Speak with a healthcare provider to determine whether a pneumonia vaccine is appropriate for you and which one, especially if you are over age 65 or never received a vaccine series as a child. Talk to your local pharmacist about a pneumonia vaccine if you do not have a primary care provider.

Other Tips

In addition to preventive vaccines, there are other things you can do to help reduce your chances of getting and spreading pneumonia.

Wash your hands with warm, soapy water for at least 20 seconds at a time throughout the day, particularly after using the restroom, before eating, and when returning home from being out. Clean and disinfect surfaces that are touched frequently.

Additionally, cover your mouth with your elbow when you sneeze or cough to help prevent the spread of germs. Avoid sharing straws, cups, and utensils with others, especially those who are sick or have recently been sick.

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