Another word for a germ, a microorganism, especially one which causes a disease.

An illness or sickness that has specific signs or symptoms that can be seen.

An organism that lives in or on an organism of another species and benefits by getting nutrients at the other’s expense.

An infectious agent of small size that can only reproduce in living cells of animals, plants, or bacteria.

Microscopic living organisms that can be found everywhere. They can cause infection or be beneficial.

Any of a group of spore-producing organisms feeding on organic matter.