Final answer:
An opportunistic infection is caused by a normally harmless microorganism affecting individuals with compromised immune systems.
Explanation:
An opportunistic infection is caused by a microorganism that is normally beneficial or harmless to humans but can lead to disease in individuals with weakened immune systems or compromised defenses. These infections typically occur when the microorganism takes advantage of a host's vulnerability.
For example, the body's normal microbiota can become opportunistic pathogens if they enter areas they usually do not inhabit, causing illness in the host. Individuals with conditions like HIV/AIDS or those undergoing chemotherapy are at higher risk for opportunistic infections.
Understanding pathogenicity, virulence, and host-microbe interactions is crucial to determining the likelihood of opportunistic infections and the impact they have on individuals' health.
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