Opportunistic infections. How is it that some microbe (say a bacteria) that has no virulence factors and doesn’t cause disease in a healthy individual all of the sudden do when said individual’s immune system is weak?

Question

Opportunistic infections. How is it that some microbe (say a bacteria) that has no virulence factors and doesn’t cause disease in a healthy individual all of the sudden do when said individual’s immune system is weak?

In: Biology

Answer 1

Many microbes are only harmless to us because they are quickly annihilated by a healthy immune system in normal circumstances. When that immune response is dampened, those microbes can take hold and cause illness that we wouldn’t experience otherwise.