Unit 12: Fighting Disease (Ch. 17)

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%.

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

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.

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.

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.

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

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

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).

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