1. Lesson Overview
35.1 Infectious Diseases

2. THINK ABOUT IT
For thousands of years, people believed that diseases were caused by curses, evil spirits, or vapors rising from foul marshes or dead plants and animals. In fact, malaria was named after the Italian words mal aria, meaning “bad air.”
This isn’t all that surprising, because, until microscopes were invented, most causes of disease were invisible to the human eye!

3. Causes of Infectious Disease
DO NOT WRITE: 1900s, Louis Pasteur & Robert Koch established a scientific explanation for disease.
Pasteur’s & Koch’s experiments led them to conclude that infectious diseases are caused by microorganisms.
Microorganisms were commonly called “germs”
-germ theory of disease.

4. Agents of Disease
Pathogens—organisms that invade the body and disrupt its normal functions.
Ex.) viruses, bacteria, single-celled eukaryotes, fungi, and parasites.

5. Agents of Disease 3 main ways diseases are spread:
Viruses are nonliving particles that replicate by inserting their genetic material into a host cell
ex) common cold, influenza, chicken pox, and warts.
Bacteria cause disease by breaking down the tissues or by releasing toxins
ex.) streptococcus, diphtheria, botulism & anthrax.
Fungus may infect the surface of the skin, mouth, throat, fingernails and toenails.
ex.) athlete’s foot & ringworm

6. How Diseases Spread How are infectious diseases spread?
Some through coughing, sneezing, physical contact, or exchange of body fluids.
Contaminated water or food.
From infected animals (vectors)