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 pneumonia is more likely to have 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 cases of 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. 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.¹

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.