Lungs: Normal


  • Pneumonia is an infection in one or both of your lungs. Many different germs, such as bacteria, viruses, and fungi, can cause pneumonia.
  • The infection causes air sacs in the lungs, called alveoli, to become inflamed. The air sacs may fill up with fluid or pus, causing symptoms such as a cough (with phlegm), fever, chills, and trouble breathing.
  • Pneumonia and its symptoms can vary from mild to severe. Many factors affect how serious pneumonia is, including the type of germ causing the infection and the person's age and overall health.
  • "Walking pneumonia" is a term used to describe a relatively mild case of pneumonia that does not keep someone bedridden.
  • Pneumonia tends to be more serious for infants and young children, older adults (people 65 years or older), people who have other chronic health problems, and people who have weakened immune systems as a result of diseases or medications that they may be taking.
  • Treatment for pneumonia depends on its cause, how severe your symptoms are, and your age and overall health. The goals of treatment are to cure the infection and prevent complications. People who have more severe symptoms or underlying health problems may need treatment in the hospital.
  • Pneumonia can be very serious and even life threatening. When possible, take steps to prevent the infection. Vaccines are available to help prevent pneumonia causes by pneumococcocus (strep pneumonia) and the flu (influenza).
  • It may take time to recover from pneumonia. Some people feel better and are able to return to their normal routines within a week. For other people, it can take a month or more. Talk to your doctor about when you can go back to your normal routine.

PneumoniaWhat causes pneumonia?

Many different germs can cause pneumonia. These include different kinds of bacteria, viruses, and, less often, fungi.

Most of the time, the body filters germs out of the air that we breathe to protect the lungs from infection. Sometimes, though, germs manage to enter the lungs and cause infections. This is more likely to occur if someone's immune system is weakened, or a germ is especially "virulent" or infectious.

When germs do reach your lungs, your immune system goes into action. It sends many kinds of cells to attack the germs. These cells cause the alveoli (air sacs) to become red and inflamed and to fill up with fluid and pus. This causes the symptoms of pneumonia.

Germs that can cause pneumonia


Bacteria are the most common cause of pneumonia in adults. Some people, especially the elderly and those who are disabled, may get bacterial pneumonia after having the flu or even a common cold. Dozens of different types of bacteria can cause pneumonia. Bacterial pneumonia can occur on its own or develop after you've had a cold or the flu.

The most common cause of pneumonia in the United States is the bacterium Streptococcus pneumoniae, or pneumococcus.

Another type of bacterial pneumonia is called atypical pneumonia. Atypical pneumonia includes:

  • Legionella pneumophila. This is sometimes called Legionnaire's disease. This type of pneumonia has caused serious outbreaks. Outbreaks have been linked to exposure to cooling towers, whirlpool spas, and decorative fountains.
  • Mycoplasma pneumonia. This is a common type of pneumonia that usually affects people younger than 40. People who live or work in crowded places like schools, homeless shelters, and prisons are most likely to get it. It’s usually mild and responds well to treatment with antibiotics. But, it can be very serious in some people. It may be associated with a skin rash and hemolysis (the breakdown of red blood cells).
  • Chlamydophila pneumoniae. This kind of pneumonia can occur all year and is often mild. The infection is most common in people 65 to 79 years of age.


Respiratory viruses cause up to one-third of the pneumonia cases in the United States each year. These viruses are the most common cause of pneumonia in children younger than 5 years. Most cases of viral pneumonia are mild. They get better in about 1 to 3 weeks without treatment. Some cases are more serious and may require treatment in a hospital.

If you have viral pneumonia, you alo run the risk of getting bacterial pneumonia.

The flu virus is the most common cause of viral pneumonia in adults. Other viruses that cause pneumonia include respiratory syncytial virus, rhinovirus, herpes simplex virus, severe acute respiratory syndrome (SARS), and more.


Three types of fungi in the soil in some parts of the U.S. can cause pneumonia. These fungi are:

  • Coccidioidomycosis in Southern California and the Southwest desert
  • Histoplasmosis in the Ohio and Mississippi River Valleys
  • Cryptococcus.

Most people exposed to these fungi don’t get sick, but some do and require treatment.

Who is at risk for pneumonia?

Pneumonia can affect people of all ages. However, two age groups are at greater risk of developing pneumonia:

  • Infants who are 2 years or younger, because their immune systems are still developing during the first few years of life
  • People who are 65 years or older

Other conditions and factors also raise your risk for pneumonia. You’re more likely to get pneumonia if you have a lung disease or other serious disease. Examples include cystic fibrosis, asthma, COPD (chronic obstructive pulmonary disease), bronchiectasis, diabetes, heart failure, and sickle cell anemia.

Having a weak or suppressed immune system also can raise your risk. A weak immune system may be the result of a disease such as HIV/AIDS. A suppressed immune system may be due to an organ or bone marrow transplant, chemotherapy (treatment for cancer), or long-term steroid use.

Your risk also goes up if you have trouble coughing because of a stroke, trouble swallowing, limited ability to move, alcohol use, or sedation (being given medicine to make you relaxed or sleepy).

Smoking cigarettes, abusing alcohol, and being undernourished also raise your risk for pneumonia. Your risk also goes up if you’ve recently had a cold or the flu, or if you’re exposed to certain chemicals, pollutants, or toxic fumes.

What are the signs and symptoms of pneumonia?

The symptoms of pneumonia vary from mild to severe. Many factors affect how serious pneumonia is, including the type of germ causing the infection and your age and overall health.

See your doctor promptly if you:

  • Have a high fever
  • Have shaking chills
  • Have a cough with phlegm, which doesn’t improve or worsens
  • Develop shortness of breath with normal daily activities
  • Have chest pain when you breathe or cough
  • Feel suddenly worse after a cold or the flu

People with pneumonia may have other symptoms, including nausea (feeling sick to your stomach), vomiting, and diarrhea.

Symptoms may vary in certain populations. Newborns and infants may not show any signs of the infection or may vomit, have a fever and cough, or appear restless, sick, or tired and without energy.

Older adults and people who have serious illnesses or weak immune systems may have fewer and milder symptoms. They may even have a lower than normal temperature. If they already have a lung disease, it may get worse. Older adults who have pneumonia sometimes have sudden changes in mental awareness.

Complications of pneumonia

Often, people who have pneumonia can be treated successfully and not have complications. But some patients, especially those in high-risk groups, may have complications such as:

  • Bacteremia. This serious complication occurs when the infection moves into your bloodstream. From there, it can quickly spread to other organs, including your brain.
  • Lung abscess. An abscess occurs when pus forms in a cavity in the lung. An abscess usually is treated with antibiotics. In some cases, surgery or needle drainage is needed to remove it.
  • Pleural effusion. Pneumonia may cause fluid to build up in the pleural space, which is the space between your lungs and chest wall. Pneumonia can cause the fluid to become infected—a condition called empyema. If this happens, you may need to have the fluid drained through a chest tube or removed through surgery.

How is pneumonia diagnosed?

Pneumonia can be hard to diagnose because it may seem like a cold or the flu. People may not realize it’s more serious until it lasts longer than these other conditions.

Your doctor will diagnose pneumonia based on your medical history and the results from a physical exam and tests.

Your doctor will listen to your lungs with a stethoscope. If you have pneumonia, your lungs may make crackling, bubbling, and rumbling sounds when you inhale. It may be hard to hear sounds of breathing in some areas of your chest. Your doctor also may hear wheezing.

If your doctor suspects you have pneumonia, he or she also may order one or more of the following tests.

Chest X-ray A chest X-ray is a painless test that creates pictures of the structures inside your chest, such as your heart and lungs. A chest X-ray is the best test for diagnosing pneumonia. However, this test won’t tell your doctor what kind of germ is causing the pneumonia.

Blood tests. Blood tests involve taking a sample of blood from a vein in your body. A complete blood count (CBC) measures many parts of your blood, including the number of white blood cells in the blood sample. The number of white blood cells can show whether you have a bacterial infection. Your doctor also may order a blood culture to find out whether the infection has spread to your bloodstream. This test is used to detect germs in the bloodstream. It may show which germ caused the infection. If so, your doctor can decide how to treat the infection.

Other tests. You may need other tests if you’re in the hospital, have serious symptoms, are older, or have other health problems.

  • Sputum test. Your doctor may look at a sample of sputum (spit) collected from you after a deep cough. This may help your doctor find out what germ is causing your pneumonia. Then, he or she can plan treatment.
  • Chest CT scan. A chest CT scan is a painless test that creates precise pictures of the structures in your chest, such as your lungs. A chest CT scan is a kind of X-ray, but its pictures show more detail than those of a standard chest X-ray.
  • Pleural fluid culture. For this test, a sample of fluid is taken from the space between your lungs and chest wall (the pleural space). This is done using a procedure called thoracentesis. The fluid is studied for germs that may cause pneumonia.
  • Pulse oximetry. For this test, a small clip is attached to your finger or ear to show how much oxygen is in your blood. Pneumonia can keep your lungs from moving enough oxygen into your bloodstream.If you’re very sick, your doctor may need to measure the level of oxygen in your blood using a blood sample. The sample is taken from an artery, usually in your wrist.
  • Bronchoscopy. Bronchoscopy is used to look inside the lungs' airways. If you’re in the hospital and treatment with antibiotics isn’t working well, your doctor may use this test. Your doctor passes a thin, flexible tube with a camera on its tip through your nose or mouth, down your throat, and into the airways.This test allows your doctor to see whether something is blocking your airways or whether another factor is contributing to your pneumonia.

How Is pneumonia treated?

Treatment for pneumonia depends on the type of pneumonia you have and how severe it is. Most people who have community-acquired pneumonia, the most common type of pneumonia, are treated at home. The goals of treatment are to cure the infection and prevent complications.

General treatment

It’s important to follow your treatment plan, take all medicines as prescribed, and get ongoing medical care. Talk to your doctor about when you should schedule followup care. Your doctor may want you to have a chest X-ray to make sure the pneumonia is gone.

Although you may start feeling better after a few days or weeks, fatigue (tiredness) can persist for up to a month or more. People who are treated in the hospital may need at least 3 weeks before they can go back to their normal routines.

Bacterial pneumonia

Bacterial pneumonia is treated with antibiotics. You should take antibiotics as your doctor prescribes. You may start to feel better before you finish the medicine, but you should continue taking it as prescribed. If you stop too soon, the pneumonia may come back. Most people begin to improve after 1 to 3 days of antibiotic treatment. This means that they should feel better and have fewer symptoms, such as cough and fever.

Viral pneumonia

Viral pneumonia isn't treated with antibiotics. This type of medicine doesn't work when a virus causes the pneumonia. If you have viral pneumonia, your doctor may prescribe an antiviral medicine to treat it. Viral pneumonia usually improves in 1 to 3 weeks.

Treating severe symptoms

You may need to be treated in a hospital if your symptoms are severe or you’re at risk for complications because of other health problems.

If the level of oxygen in your bloodstream is low, you may receive oxygen. If you have bacterial pneumonia, your doctor may give you antibiotics through an intravenous (IV) line inserted into a vein.

How can pneumonia be prevented?

Pneumonia can be very serious and even life threatening. When possible, take steps to prevent the infection, especially if you’re in a high-risk group.


Vaccines can’t prevent all cases of infection. However, compared to people who don’t get vaccinated, those who do and still get pneumonia tend to have:

  • Milder cases of the infection
  • Pneumonia that doesn’t last as long
  • Fewer serious complications

The pneumococcal pneumonia vaccine is available to prevent pneumococcal pneumonia. In most people, one shot is good for at least 5 years of protection.

The flu vaccine is available to prevent seasonal influenza and reduce the risk of developing pneumonia from seasonal flu. It is effective only for one year and is usually available in October or November, before peak flu season.

The Hib vaccine is recommended for all children in the United States who are younger than 5 years. It’s often given to infants starting at 2 months of age to prevent infections by Haemophilus influenzae type b (Hib), a type of bacteria that can cause pneumonia and meningitis (an infection of the covering of the brain and spinal cord).

Other ways to prevent pneumonia

  • Wash your hands with soap and water or alcohol-based rubs to kill germs.
  • Don’t smoke. Smoking damages your lungs’ ability to filter out and defend against germs.
  • Keep your immune system strong. Get plenty of rest and physical activity and follow a healthy diet.

If you have pneumonia, limit contact with family and friends. Cover your nose and mouth while coughing or sneezing, and dispose of tissues right away. These measures help keep the infection from spreading.

© 2010 Vivacare. Last updated June 23, 2011.

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Additional Resources

Pneumonia Overview (link to NIH)
Mycoplasma Test (link to American Association for Clinical Chemistry)
En Espanol
Neumonia (link to NIH)
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