Key terms

6. tiny, single-celled organisms that get nutrients from their environments.
8. a diverse group of minute, simple forms of life that include bacteria, algae, fungi, protozoa, and viruses.
10. simple organisms, or living things.
11. against a disease, they are purposely given the bacteria or virus that causes the disease.

1. an infectious disease that spreads among many people over a wide.
2. disease that quickly infects a large number of people.
3. Bacteria, virus, fungi, or protist.
4. a very tiny type of germ.
5. the branch of medical science concerned with disease occurrence, distribution, and control within a population.
7. the fact or condition of being affected by something or experiencing something.
9. an outbreak of a disease that quickly infects a large number of people.