Across
- 3. spread to everyone
- 4. bacteria
- 6. system organs that protects the body from infections
- 7. a period of 100 years
- 9. illness
- 11. virus
Down
- 1. hard, difficult
- 2. a way doing things
- 5. the person idea
- 7. treat
- 8. something that causes disease
- 10. a period of time