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Written by Ada’s Medical Knowledge Team

Updated on

What is pneumonia?

Pneumonia is an infection of the air sacs (alveoli) in the lungs, which inflames them and causes them to fill with fluid or pus.

This interferes with the lungs’ ability to breathe and properly supply oxygen to the body, causing symptoms ranging from coughing, fever and shortness of breath to more severe ones. The infection causes inflammation which can affect the tissue in several areas, including:

  • The bronchi in the lungs, called bronchial pneumonia (bronchopneumonia)
  • One or more segments of the lungs (segmental pneumonia)
  • The tissue between the alveoli (interstitial pneumonia)

Types of pneumonia

There are over 30 different causes of pneumonia, including bacteria, viruses, fungi and chemicals. 1 The cause affects the symptoms and treatment of the condition.

Pneumonia is also described according to where it was acquired, with hospital-acquired pneumonia (HAP) considered more serious than community-acquired pneumonia (CAP) because of the possibility of infection with antibiotic-resistant bacteria in a hospital setting.

Bacterial pneumonia

Most often caused by Streptococcus pneumoniae (S. pneumoniae), bacterial pneumonia occurs when bacteria that live in the throat are able to enter the lungs while the body is weakened due to factors such as advanced age, illness, general poor health or a compromised immune system. 2 Other pneumonia-causing bacteria include Klebsiella pneumoniae (K. pneumoniae).

Pneumonia from Chlamydia pneumoniae

Also known as Taiwan acute respiratory agent (TWAR), Chlamydia pneumoniae is another bacteria that can cause bacterial pneumonia. Chlamydia pneumoniae symptoms may include laryngitis, unlike typical bacterial pneumonia. 3

Viral pneumonia

The same viruses that cause a cold or flu can move from the upper respiratory tract to the lungs and cause pneumonia. Viral pneumonia typically lasts for a shorter duration than bacterial pneumonia.

Walking pneumonia

Sometimes called atypical pneumonia, walking pneumonia is most often caused by the microorganism Mycoplasma pneumoniae (M. pneumoniae). Differentiating it from typical pneumonia, walking pneumonia has less severe symptoms and often does not require bed rest.

People with walking pneumonia may, in some cases, confuse the condition with a common cold and continue to go about their normal routine. These people continue to be infectious, though, for as long as 10 days. Walking pneumonia sometimes occurs alongside a skin rash, anemia or an ear infection, and can affect people of all ages. 4

Chemical and aspiration pneumonia

Inhaling harmful substances and chemicals in dust, gas or liquid form can cause pneumonia and damage the lungs. Inhaling secretions from the stomach or mouth, or substances such as vomit or food, can cause aspiration pneumonia, which inflames the lungs due to irritation from the digestive juices and can lead to bacterial pneumonia. 5

Aspiration pneumonia is more common when the person’s gag reflex has already been impaired, such as in cases of drug or alcohol abuse, brain injury or trouble swallowing. These pneumonias vary greatly in severity due to differences in substances and other factors of exposure.

Fungal pneumonia

Inhaling fungi in bird droppings or soil can lead to pneumonia, particularly among people with a weakened immune system. For this reason, infection with the fungus Pneumocystis jirovecii (Pneumocystis jirovecii pneumonia, or PCP) can be among the first signs of HIV infection. 6

Pneumonia symptoms

As pneumonia ranges in severity from mild to life-threatening and can be caused by numerous factors, there are also a wide range of symptoms. The most common symptoms of bacterial and viral pneumonia include:

  • Fever, chills, or cold sweats
  • Coughing that may or may not produce yellow, green or bloody mucus (phlegm)
  • Fatigue
  • Shortness of breath
  • Chest pain that increases with deep breaths
  • Rapid pulse
  • Fast breathing
  • Heavy perspiration
  • Confusion
  • Bluish lips or fingernails

In viral pneumonia, these symptoms may worsen to include:

  • Headache
  • Muscle aches
  • Weakness
  • More severe cough and difficulty breathing 1

Good to know: A person who has difficulty breathing, extreme chills or who is expelling green or dark mucus should contact a doctor immediately.

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Pneumonia in children

When pneumonia occurs in a child younger than 10 years of age, it is called pediatric or childhood pneumonia. Viruses are more likely than bacteria to cause pneumonia in children under five years of age, and children are also more likely than adults to contract walking pneumonia, largely due to opportunities for the disease to break out at locations such as schools and summer camps.

Most cases of childhood pneumonia are not serious, and children with pneumonia may exhibit more subtle symptoms and be less likely to have high fevers. As it is more difficult to notice pneumonia symptoms in infants, parents should be vigilant if their child vomits, appears to feel ill, is limp, pale or restless or cries more than usual.

Bacterial pneumonia tends to be more serious, but is more common among older children.

Good to know: Parents should seek immediate medical attention promptly if their child’s breathing is distressed to the point that their nostrils flare when they breathe, they are breathing quickly, or they are visibly using the accessory muscles of the belly – above the collarbones or below the ribs – to breathe. 7

Just as with adults, when a child’s immune system is compromised for reasons including recent hospitalization, asthma or chronic illness, they are at greater risk of contracting pneumonia. Children who have not received the full course of childhood vaccinations or PCV13 (Prevnar) are more likely to contract pneumonia.

Read more about Pediatric Pneumonia »

Pneumonia in older people

People older than 65 are at greater risk of pneumonia and are more likely to develop a more serious infection. People in hospitals or nursing homes are more likely to be exposed to microorganisms that can result in developing hospital acquired pneumonia, and many conditions that older people are more likely to have, such as diabetes, heart disease and lung disease, are linked to pneumonia – though it is unclear whether addressing these issues directly lessens a person’s chance of developing pneumonia. 8

Good to know: Though pneumonia symptoms experienced by older people can be similar to those among people of all ages, some older people primarily experience symptoms of fatigue or confusion.

Risk factors for pneumonia

Anyone can get pneumonia at any age, but people who are younger than two or older than 65 are at the highest risk. Also at risk are people in a weakened state of health due to illness, poor nutrition or a compromised immune system from conditions such as asthma, HIV/AIDS, lymphoma, diabetes, leukemia or heart disease. Smokers and people who abuse alcohol are also more likely to get pneumonia.

Along with these health issues, people who are hospitalized, particularly if they are using a machine for respiratory support (ventilator), are at risk of hospital-acquired pneumonia. People undergoing chemotherapy, organ donors and recipients or people on long-term steroids can have a weakened immune system that makes them more susceptible. 9

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Pneumonia diagnosis

The first step in diagnosing pneumonia is a physical examination, in which a doctor will check for rapid breathing and a blue or purple tint to the lips, fingernails or hands, which can indicate low levels of blood oxygen. As part of this check, they will use pulse oximetry to test for oxygenation in the blood, using a sensor clipped to a finger.

They will also listen to the chest using a stethoscope to check for unusual noises, such as a crackling sound.

The next step is typically a chest X-ray to confirm the diagnosis, and this confirmation may give the doctor enough information to begin treatment. 10 Depending on the symptoms and their severity, though, the doctor may request further testing including:

  • Blood tests to check for the presence, type or spread of infection, as well as the level of oxygen in the blood.
  • Sputum test to culture a sample of material coughed up from the lungs to check for infection or identify the microorganism responsible.
  • Chest CT scan to provide similar information about the presence of infection inside of the lungs as an X-ray, but in greater detail by combining computer imaging and X-ray technology.
  • Bronchoscopy to visually inspect the bronchi – the main pathways of the lungs – to evaluate the extent of the infection, as well as to take samples of tissue and fluid, using a camera attached to a flexible tube that is threaded into the airways. This test is more common in severe cases of pneumonia or if the treatment does not respond to antibiotics.
  • Pleural fluid sample to check fluid between the lungs and the chest wall for infection, using a long, thin needle.

Pneumonia treatment

Antibiotics may be used to treat bacterial, mycoplasmal and some other types of pneumonia, and antifungal medications may be used for fungal pneumonia. Viral pneumonia cannot be treated with antibiotics, but it usually resolves on its own. 1

Most people recover at home rather than at the hospital. The most common treatment for pneumonia involves supporting the body’s health and immune system, such as improving the affected person’s diet, fluid intake or rest. Other treatments may include lowering the fever or administering oxygen. A younger person might recover from pneumonia in a few days while taking antibiotics, while a person over 60 years of age or who has a chronic health condition might be hospitalized for monitoring and treatment.

Some people take over-the-counter-painkillers such as aspirin, acetaminophen (Tylenol) or ibuprofen (Advil). Although some people use cough suppressants, some coughing is necessary to remove built-up fluid and mucus from the lungs and airways.

Possible complications of pneumonia

Most people treated for pneumonia recover successfully, but, in some cases, it can be a life-threatening condition. People who are very young or over 60 years of age, or who have chronic health conditions, are at greater risk of complications. These can include respiratory failure or its more extreme form, acute respiratory distress syndrome (ARDS), which might require a person to be treated with a ventilator or respirator.

If the infection enters the bloodstream, sepsis can occur. Sometimes, pneumonia can cause empyema, in which infected packets of pus and fluid collect along or inside the lungs, and may need to be treated with surgery.

Pneumonia can worsen some chronic conditions, such as emphysema and congestive heart failure. It can also make some people more likely to have a heart attack. 6

Feeling unwell? Start your free symptom assessment in the Ada app

Pneumonia prevention

Two vaccines, PCV13 (Prevnar 13) and PPSV23 (Pneumovax), are available in the US to prevent pneumonia. These vaccines cannot prevent all cases of pneumonia, but if a vaccinated person contracts pneumonia, it is likely to be of shorter duration and with fewer complications. Both vaccines are recommended for older people. 11

Children younger than five should receive a series of four vaccinations with PCV13. There is some evidence that zinc supplementation can prevent pneumonia in children. 12 Keeping up-to-date with vaccinations and maintaining overall good health can help older people prevent pneumonia.

People with some chronic health conditions may be offered these vaccinations and people between 19-64 years of age who smoke might consider being vaccinated with Pneumovax – though quitting smoking will make them less vulnerable to pneumonia and other infections.

A flu shot can be helpful in preventing all types of pneumonia; the body is more likely to be susceptible to pneumonia, and other infections when its immune system is weakened by flu.

Anyone can follow basic precautions to prevent pneumonia, including washing their hands regularly to avoid the spread of infection and maintaining a healthy lifestyle, such as eating a healthy diet and getting enough rest and exercise.

Pneumonia FAQs

Q: Is pneumonia contagious?
A: Pneumonia itself is not contagious, but the bacteria, viruses and other microorganisms that lead to this kind of infection can be communicated from person to person. Therefore, the same precautions that prevent the spread of cold and flus can also help prevent transmission of pneumonia.

Q: Which population groups should ensure that they are vaccinated against pneumonia?
A: As a matter of course, all children younger than five should receive a series of four vaccinations with PCV13 (Prevnar 13). It is recommended that adults be vaccinated against pneumonia if they meet one or more of the following criteria:

  • Are over 65
  • Use tobacco products (in particular, products which involve smoking)
  • Are affected by alcohol addiction
  • Have, or have had, cochlear implants or cerebrospinal fluid leaks
  • Are affected by ongoing conditions, such as diabetes, diseases of the heart, lungs, spleen or kidneys, or conditions with compromise the function of the immune system, such as HIV.

Q: What are the differences between pneumonia and double pneumonia?
A: It is possible to be affected by pneumonia in one or both lungs. Double pneumonia is a term used to refer to cases where both of a person’s lungs are infected. It is a common misconception that double pneumonia is more severe than pneumonia which relates to one lung. In fact, it is equally possible to be affected by a mild infection in both lungs, as it is for a severe infection to affect one lung. The potential causes, symptoms, risk factors and treatment options for pneumonia are the same whether it is double or not. Always seek medical attention promptly if pneumonia is suspected.