Many disorders, drugs, 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.
Drugs that suppress the immune system:
Radiation treatments: Such treatments may suppress the immune system, particularly when bone marrow is exposed to radiation.
AIDS: The ability to fight certain infections decreases dramatically in people with AIDS, especially late in the disease. People with AIDS 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 AIDS 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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