1. Unit 12:
Fighting Disease (Ch. 17)

2. A little history…
Before 1900s, surgery was very risky. About 45% of all people who had surgery died. People didn’t know that microorganisms existed.
Joseph Lister- 1860s- surgeon who washed his hands before surgery and covered wounds with bandages. Reduced surgery deaths to about 15%.

3. A little history…
Louis Pasteur- 1860s- boiled beef broth to kill microorganisms.
Robert Koch- proved that each sickness is caused by a different microorganism.

5. Infectious Disease Pathogen- organism that causes disease
Infectious disease- caused by a living thing in the body (pathogen gets inside body).
Pathogens damage individual cells.
4 classes of pathogens: bacteria, viruses, fungi, protists.

6. Bacteria Single-celled organisms
Cause ear infections, strep throat, food
poisoning, etc.
Some bacteria damage cells directly, others release toxins.
Toxin- a poison that damages cells.
Tetanus (lockjaw) - bacteria get into wound and release toxin that damages nervous system.

8. Viruses Much smaller than bacteria.
Viruses aren’t alive! They cannot reproduce unless they are in a living cell.
Ex: cold and flu.
Not treated with antibiotics.

10. Fungi
Grow best in dark, warm places.
Ex: Athlete’s Foot and Ringworm

11. Protists
Unicellular organisms, live in water, soil, and other environments.
Malaria- blood infection, common in tropical areas, spread by mosquitoes.

12. How Disease Spreads
Contact with infected people- hugging, kissing, shaking hands, drinking, sneezing, coughing.
Soil, Food, Water- live in soil and spread through unclean food or water.
Contaminated Objects- microorganisms live on surfaces (cold and flu spread this way).

13. Infected Animals- Animals/insects bite people and spread disease (Lyme Disease from ticks, Malaria from mosquitoes).