What is an opportunistic infection?

An opportunistic infection is defined as an infection that typically occurs in individuals with weakened or compromised immune systems. This type of infection takes advantage of the body's reduced ability to fight off pathogens, which can be due to various factors such as underlying diseases (like HIV/AIDS, cancer, or diabetes), medical treatments (such as chemotherapy or immunosuppressive drugs), or other conditions that impair immune function.

In healthy individuals, the immune system is generally effective at preventing infections from a wide array of pathogens, including those that are typically harmless or benign. However, when the immune defenses are compromised, these pathogens can take the opportunity to cause infections. For instance, organisms that do not normally cause disease in healthy people can lead to severe infections in immunocompromised individuals.

This characteristic of opportunistic infections highlights their dependence on the host's immune status, distinguishing them from infections that can occur in healthy individuals, which are not classified as opportunistic.