Pneumonia is a lung infection that can make you very sick. You may cough, run a fever, and have a hard time breathing. For most people, pneumonia can be treated at home. It often clears up in 2 to 3 weeks.


But older adults, babies, and people with other diseases can become very ill. They may need to be in the hospital.You can get pneumonia in your daily life, such as at school or work. This is called community-associated pneumonia.


You can also get it when you are in a hospital or nursing home. This is called healthcare-associated pneumonia. It may be more severe because you already are ill. This topic focuses on pneumonia you get in your daily life.


Symptoms of pneumonia caused by bacteria usually come on quickly.


They may include:


  • Cough. You will likely cough up mucus (sputum) from your lungs. Mucus may be rusty or green or tinged with blood.
  • Fever.
  • Fast breathing and feeling short of breath.
  • Shaking and "teeth-chattering" chills. You may have this only one time or many times.
  • Chest pain that often feels worse when you cough or breathe in.
  • Fast heartbeat.
  • Feeling very tired or feeling very weak.
  • Nausea and vomiting.
  • Diarrhea.


When you have mild symptoms, your doctor may call this "walking pneumonia".


Older adults may have different, fewer, or milder symptoms. They may not have a fever. Or they may have a cough but not bring up mucus. The main sign of pneumonia in older adults may be a change in how well they think. Confusion ordelirium is common. Or, if they already have a lung disease, that disease may get worse.


Symptoms caused by viruses are the same as those caused by bacteria. But they may come on slowly and often are not as obvious or as bad.


Many germs can cause pneumonia. Examples 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. Your immune system, the shape of your nose and throat, your ability tocough, and fine, hair-like structures called cilia (SIL-e-ah) help stop the germs from reaching your lungs (for more information, go to the Diseases and Conditions Index How the Lungs Work article).


Sometimes, though, germs manage to enter the lungs and cause infections.


This is more likely to occur if:


  • Your immune system is weak.
  • A germ is very strong.
  • Your body fails to filter germs out of the air that you breathe.


For example, if you can't cough because you've had a stroke or are sedated, germs may remain in your airways ("sedated" means you're given medicine to make you sleepy).


When germs 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.


Many types of bacteria can cause pneumonia. Bacterial pneumonia can occur on its own or develop after you've had a cold or the flu. This type of pneumonia often affects one lobe, or area, of a lung. When this happens, the condition is called lobar pneumonia.


The most common cause of pneumonia in the United States is the bacterium Streptococcus (strep-to-KOK-us) pneumoniae, or pneumococcus (nu-mo-KOK-us).


Another type of bacterial pneumonia is called atypical pneumonia.


Atypical pneumonia includes:


  • Legionella pneumophila. This type of pneumonia sometimes is called Legionnaire's disease, and it 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 years old. People who live or work in crowded places like schools, homeless shelters, and prisons are at higher risk for this type of pneumonia. It's usually mild and responds well to treatment with antibiotics. However, mycoplasma pneumonia can be very serious. It may be associated with a skin rash and hemolysis (the breakdown of red blood cells).
  • Chlamydophila pneumoniae. This type of pneumonia can occur all year and often is mild. The infection is most common in people 65 to 79 years old.



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 old.


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 run the risk of getting bacterial pneumonia as well.


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 United States can cause pneumonia.


These fungi are:

  • Coccidioidomycosis (kok-sid-e-OY-do-mi-KO-sis). This fungus is found in Southern California and the desert Southwest.
  • Histoplasmosis (HIS-to-plaz-MO-sis). This fungus is found in the Ohio and Mississippi River Valleys.
  • Cryptococcus (krip-to-KOK-us). This fungus is found throughout the United States in bird droppings and soil contaminated with bird droppings.


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


Serious fungal infections are most common in people who have weak immune systems due to the long-term use of medicines to suppress their immune systems or having HIV/AIDS.


Pneumocystis jiroveci (nu-mo-SIS-tis ye-RO-VECH-e), formerly Pneumocystis carinii, sometimes is considered a fungal pneumonia. However, it's not treated with the usual antifungal medicines.


This type of infection is most common in people who:

  • Have HIV/AIDS or cancer.
  • Have had an organ transplant and/or blood and marrow stem cell transplant.
  • Take medicines that affect their immune systems.


Other kinds of fungal infections also can lead to pneumonia.


Doctors use antibiotics to treat pneumoniacaused by bacteria, the most common cause of the condition. The number of days you take antibiotics depends on your general health, how serious your pneumonia is, and the type of antibiotic you are taking.


Your doctor will choose your antibiotic based on a number of things, including your age, your symptoms and how severe they are, and whether you need to go to the hospital.


Although experts differ on their antibiotic recommendations, the first antibiotic used usually is one that works against a wide range of bacteria (broad-spectrum antibiotic). All antibiotics used have a high cure rate for pneumonia.


If you do not have to go to the hospital, your doctor may use any of the following antibiotics:


  • Macrolides, such as azithromycin,clarithromycin, and erythromycin.
  • Tetracyclines, such as doxycycline.
  • Fluoroquinolones, such as gemifloxacin,levofloxacin, and moxifloxacin.


If you have to go to the hospital, your doctor may use any of the above antibiotics.


Other antibiotics that your doctor may use in this situation include:


  • Cephalosporins, such as ceftriaxone, cefotaxime, and cefepime.
  • Penicillins, such as amoxicillin and ampicillin.
  • Vancomycin.


Antibiotics usually work well with younger, otherwise healthy people who have strong immune systems. You most likely will see some improvement in symptoms in 2 to 3 days. Unless you get worse during this time, your doctor usually will not change your treatment for at least 3 days. If there is no improvement or if your symptoms get worse, you may need culture and sensitivity testing. These tests help identify the organism that is causing your symptoms. These tests also help your doctor find out whether the bacteria may be resistant to the antibiotic.


You likely will not have to go to the hospital unless you:


  • Are older than 65.
  • Have other health problems, such as chronic obstructive pulmonary disease,heart failure, asthma, diabetes, long-term (chronic) kidney failure, or chronic liver disease.
  • Cannot care for yourself or would not be able to tell anyone if your symptoms got worse.
  • Have severe illness with less oxygen getting to the tissues (hypoxia).
  • Have chest pain caused by inflammation of the lining of the lung (pleurisy) so you are not able to cough up mucus effectively and clear your lungs.
  • Are being treated outside a hospital and are not getting better (such as your shortness of breath not improving).
  • Are not able to eat or keep food down so you need to take fluids through a vein (intravenous).


Viral pneumonia


Pneumonia also can be caused by viruses, such as those that cause influenza (flu) and chickenpox (varicella).

  • At this time, there is no proven medicine to treat pneumonia caused by the influenza virus. Home treatment, such as rest and taking care of your cough, is the only treatment.
  • Varicella pneumonia, which is rare, can be treated with antiviral medicine.
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