It normally starts with a bacterial, viral, or fungal infection.
The lungs become inflamed, and the tiny air sacs, or alveoli, inside the lungs fill up with fluid.
Pneumonia can occur in young and healthy people, but it is most dangerous for older adults, infants, people with other diseases, and those with impaired immune systems.
In the United States (U.S.), around 1 million people are treated in the hospital for pneumonia each year, and around 50,000 die from the disease.
Here are some key points about pneumonia. More detail is in the main article.
- Pneumonia is an infection of the lungs that can cause mild to severe illness in people of all ages.
- It is the leading cause of death due to infection in children younger than 5 years of age worldwide.
- Pneumonia and influenza together are ranked as the eighth leading cause of death in the U.S.
- Those at high risk for pneumonia include older adults, the very young, and people with underlying health problems.
Causes and risk factors
Pneumonia is a serious lung infection with a number of possible causes.
Bacteria and viruses are the main causes of pneumonia. Pneumonia-causing germs can settle in the alveoli and multiply after a person breathes them in.
Pneumonia can be contagious. The bacteria and viruses that cause pneumonia are usually inhaled.
They can be passed on through coughing and sneezing, or spread onto shared objects through touch.
The body sends white blood cells to attack the infection. This is why the air sacs become inflamed. The bacteria and viruses fill the lung sacs with fluid and pus, causing pneumonia.
Those most at risk include people who:
- are aged under 5 years or over 65 years
- smoke tobacco, consume large amounts of alcohol, or both
- have underlying conditions such as cystic fibrosis, chronic obstructive pulmonary disorder (COPD), asthma, or conditions that affect the kidneys, heart, or liver
- have a weakened or impaired immune system, due, for example, to AIDS, HIV, or cancer
- take medicines for gastroesophageal reflux disease (GERD)
- have recently recovered from a cold or influenza infection
- experience malnutrition
- have been recently hospitalized in an intensive care unit
- have been exposed to certain chemicals or pollutants
Some groups are more prone than others to pneumonia, including Native Alaskan or certain Native American ethnicities.
Types of pneumonia
There are different types of pneumonia, depending on their cause.
- Bacterial pneumonia: The most common cause is the bacterium Streptococcus pneumoniae (S. pneumoniae), but many different bacteria can cause pneumonia
- Viral pneumonia: This can result from the respiratory syncytial virus (RSV) and influenza types A and B, known as the flu
- Aspiration pneumonia: This can happen when a person breathes food, liquids, or stomach contents into the lungs. This type is not contagious.
- Fungal pneumonia: This can result from a condition such as valley fever, caused by the Coccidioides fungus.
- Hospital-acquired pneumonia: This can occur in patients being treated for other conditions, for example, those attached to a respirator, or breathing machine.
Regardless of the cause, the signs and symptoms will be similar.
The first symptoms of pneumonia usually resemble those of a cold or flu. The person then develops a high fever, chills, and cough with sputum.
Common symptoms include:
- rusty or green phlegm, or sputum, coughed up from lungs
- fast breathing and shortness of breath
- shaking chills
- chest pain that usually worsens when taking a deep breath, known as pleuritic pain
- fast heartbeat
- fatigue and weakness
- nausea and vomiting
- muscle pain
- confusion or delirium, especially in older adults
- dusky or purplish skin color, or cyanosis, from poorly oxygenated blood
Symptoms can vary depending on other underlying conditions and the type of pneumonia.
A doctor will ask about symptoms and medical history and will carry out a physical examination.
An X-ray can show if there is any damage to the lungs.
They may suspect pneumonia if they hear coarse breathing, wheezing, crackling, or decreased breath sounds when listening to the chest through a stethoscope.
The doctor may also check the oxygen levels in the blood with a painless monitor on the finger called a pulse oximeter.
Chest X-rays can confirm a pneumonia diagnosis and show which areas of the lungs are affected.
A CT scan of the chest may provide more detailed information.
Blood tests measure the white blood cell count.
This helps determine how severe the infection is, and whether a bacteria, virus, or fungus is the likely cause.
Blood cultures may reveal whether the microorganism from the lungs has spread into the blood stream.
An arterial blood gas (ABG) blood test may provide a more accurate reading of the body's oxygen and carbon dioxide levels and other factors.
A sputum analysis can determine which organism is causing the pneumonia.
A bronchoscopy is sometimes used for further investigation.
A thin, flexible, and lighted tube called a bronchoscope is passed down into the lungs. This enables the doctor to examine directly the infected parts of the airways and lungs. The patient is under anesthetic.
Treatment depends on the type and severity of the pneumonia.
- Bacterial types of pneumonia are usually treated with antibiotics.
- Viral types of pneumonia are usually treated with rest and plenty of fluids. Antiviral medications can be used in influenza.
- Fungal types of pneumonia are usually treated with antifungal medications.
Doctors commonly prescribe over-the-counter (OTC) medications to help manage the symptoms of pneumonia. These include treatments for reducing fever, reducing aches and pains, and suppressing coughs.
In addition, it is crucial to rest and drink plenty of fluids. Staying hydrated helps to thin out thick phlegm and mucus, making it easier to cough up.
Hospitalization for pneumonia may be required if symptoms are especially bad or if an individual has a weakened immune system or other serious illnesses.
In the hospital, patients are generally treated with intravenous antibiotics and fluids. They may need a supplemental oxygen supply.
There are two different vaccines to prevent pneumococcal disease, the most common bacterial cause of pneumonia.
These cover a wide variety of pneumococcal infections and are recommended for both children and adults, depending on their health conditions.
- pneumococcal conjugate vaccine, or Prevnar
- pneumococcal polysaccharide vaccine, or Pneumovax
Keeping to a vaccination schedule can help prevent infection.
Prevnar (PCV13) is normally included as part of an infant's routine immunizations.
It is recommended for children under 2 years, adults over 65 years, and those between the ages of 2 and 64 years with certain medical conditions.
Pneumovax (PPSV23) is recommended for children and adults who are at increased risk of developing pneumococcal infections.
- adults aged 65 years or older
- people with diabetes
- those with chronic heart, lung, or kidney disease
- people who consume large amounts of alcohol or who smoke
- those without a spleen
Those aged between 2 and 64 years with certain other medical conditions may be advised to have this vaccine
The vaccine may not completely protect older adults from pneumonia, but it can significantly reduce the risk of developing pneumonia and other infections caused by S. pneumoniae), including blood and brain infections.
Along with vaccinations, physicians recommend:
- regular hand washing
- covering the mouth and nose when coughing or sneezing
- refraining from smoking
- eating healthfully
- exercising 5 days a week
- staying away from the sputum or cough particles of others with pneumonia
Most people recover from pneumonia in 1 to 3 weeks. Those at risk of severe symptoms should ensure they keep up their vaccinations.