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Pneumonia - What Happens

After you've been infected with a pneumonia-causing organism, it takes as little as 1 to 3 days or as long as 7 to 10 days for symptoms to appear. How severe pneumonia is and how long it lasts depend on:

  • Your age and health. Older, sicker people usually have more severe cases. And their cases of pneumonia are more likely to cause complications, such as bacteria in the bloodstream (bacteremia) or throughout the body (septicemia).
  • Whether bacteria or a virus caused the pneumonia. Viral pneumonia usually is less severe than bacterial pneumonia.
  • How quickly you treat it. The sooner you treat pneumonia, the sooner symptoms go away.
  • Your immune system. People who have impaired immune systems are more likely to have more severe pneumonia than people who have healthy immune systems.

In healthy people, pneumonia can be a mild illness that is hardly noticed and clears up in 2 to 3 weeks. In older adults and in people with other health problems, recovery may take 6 to 8 weeks or longer.

Recommended Related to Lung Disease/Respiratory Problems

Understanding Pneumonia -- the Basics

Pneumonia is an inflammation of the lungs. Usually the inflammation is caused by an infection, but it can also be caused by breathing certain chemical fumes. It's a more common problem than most people think. Usually pneumonia is a mild disease, but some forms are very dangerous. In all cases, you'll need to seek care from your health care provider. Pneumonia can affect just one lobe of the right or left lung, a whole lung, or both lungs. Many different kinds of germs infect the lungs and cause...

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Going to the hospital

If you have severe pneumonia, you may have to go to the hospital:

  • In most cases of pneumonia you get in your daily life, such as at school or work (community-based pneumonia), it is not necessary to go to the hospital.1
  • About one-third of people with community-based pneumonia are age 65 or older.1 Older adults are treated in the hospital more often and stay longer for the condition than younger people.1 Pneumonia is more serious in this group, because they often have and may develop other medical problems.

Spreading pneumonia to others

If your pneumonia is caused by a virus or bacteria, you may spread the infection to other people while you are contagious. How long you are contagious depends on what is causing the pneumonia and whether you get treatment. You may be contagious for several days to a week.

If you get antibiotics, you usually cannot spread the infection to others after a day of treatment.

    This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http:// cancer .gov or call 1-800-4-CANCER.

    WebMD Medical Reference from Healthwise

    Last Updated: March 06, 2013
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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