Many disorders, medications, and other treatments can cause a breakdown in the body’s natural defenses. Such a breakdown can lead to infections, which can even be caused by microorganisms that normally live harmlessly on or in the body (resident flora). A breakdown can result from the following:
Extensive burns: Risk of infection is increased because damaged skin cannot prevent invasion by harmful microorganisms.
Medical procedures: During a procedure, foreign material may be introduced into the body, increasing the risk of infection. Such material includes catheters inserted into the urinary tract or a blood vessel, tubes inserted into the windpipe, and sutures placed under the skin.
Medications that suppress the immune system:
Radiation treatments: Such treatments may suppress the immune system, particularly when bone marrow is exposed to radiation.
Late-stage HIV infection: The ability to fight certain infections decreases dramatically in people with late-stage HIV infection. People with late-stage HIV infection are at particular risk of opportunistic infections (infections by microorganisms that generally do not cause infection in people with a healthy immune system). Also, many common infections cause people with late-stage HIV infection to become more severely ill.
(See also Overview of Infectious Disease.)
Spotlight on Aging: Infections
Infections are more likely and usually more severe in older people than in younger people for several reasons:
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