Opportunistic infections

An opportunistic infection is an infection caused by pathogens (bacteria, viruses, fungi, or protozoa) that take advantage of an opportunity not normally available, such as a host with a weakened immune system, an altered microbiota (such as a disrupted gut microbiota), or breached integumentary barriers. Many of these pathogens do not cause disease in a healthy host that has a normal immune system. [Source: Wikipedia ]