What is a key characteristic of opportunistic diseases?

A key characteristic of opportunistic diseases is that they arise when the immune system is weakened. Opportunistic infections or diseases take advantage of the compromised state of an individual's immune system, which may occur due to various factors such as certain medical conditions, treatments, or environmental factors.

For example, individuals with HIV/AIDS, cancer patients undergoing chemotherapy, or those taking immunosuppressive medications are more susceptible to these types of diseases because their bodies are less able to fend off infections that a healthy immune system would typically control or eliminate.

This characteristic differentiates opportunistic diseases from other types of diseases that may affect healthy individuals or originate from genetic factors. While some diseases might be more prevalent in specific demographics, such as the elderly, the defining aspect of opportunistic diseases is their reliance on a weakened immune state to manifest.