1. Causes of Disease Chapter 16 Section 1

2. Objectives Identify five common types of pathogen Describe three ways infectious disseases are spread Distinguish between infectious diseases and communicable diseases Identify two causes of non-infectious diseases

3. Key Terms Pathogen Infectious disease Infection Toxin Communicable disease AIDS HIV

4. Infectious Diseases Caused by a pathogen The pathogen invades the body and begins to reproduce There are five important pathogens – Bacteria – Protozoa – Fungi – Worms – Viruses

5. Bacteria Simple single celled organisms They live everywhere ◦ On every surface ◦ Including the inside and outside of your body They are microscopic ◦ Cannot be seen without “help” Some are harmful, but some are helpful ◦ Toxins result from harmful bacteria

6. Protozoa Single celled organisms Microscopic, but larger than bacteria Found in most water supplies ◦ Not bottled or filtered water ◦ Most are not dangerous

7. Fungi Molds and mushrooms are the most common examples of Fungi Many are beneficial to humans Some are pathogens ◦ Athlete’s Foot ◦ Ringworm ◦ Thrush

8. Worms Worms can enter the body in a variety of ways They are usually immature when they enter They move to specific tissues or organs as they mature Pathogenic worms ◦ From the environment  Hookworms from the soil ◦ From food  Trichina from raw or undercooked meats

9. Viruses Much smaller that most bacteria A virus is not a cell based organism ◦ It is made of a protein coat ◦ It contains a type of genetic material They only reproduce inside other cells ◦ It takes over the cell ◦ Destroys the cell ◦ Infects nearby cells

10. More about Infectious Disease The ability of one person or organism to transfer the infection to another person or organism describes a communicable disease Some diseases do not transfer well from one individual to another A highly infectious disease may stay in one kind of organism ◦ “bird flu” found in poultry ◦ Not HIV, found in several types of organism

11. AIDS AIDS is a communicable disease caused by a virus AIDS is caused by HIV It is possible to test for AIDS There are treatments, but as yet no cure for AIDS See page 522, Table 16.1 to see methods of disease transmission

12. Non-Infectious Diseases NOT caused by pathogens NOT communicable These diseases may be inherited ◦ Muscular dystrophy, sickle cell anemia, cancer These diseases may be caused by the environment or exposure to toxins ◦ Cancer, heart diseases, arthritis

13. Summary Infectious diseases are caused by pathogens ◦ Bacteria, protozoa, fungi, worms, and viruses Pathogens invade the body, reproduce, causing an infection Communicable diseases are infectious diseases that can be spread from person to person Non-infectious diseases are NOT caused by pathogens, but by genetic factors, the environment, or both

14. Definitions Pathogen is a virus or microorganism that causes disease Infectious disease is an illness caused by a pathogen Infection is the invasion and multiplication of pathogens in the body Toxin is a poisonous substance

15. Definitions Communicable disease is an infection that can be spread from person to person AIDS, (acquired immuno-deficiency syndrome) is a viral disease that destroys the body’s ability to resist other diseases by disrupting the immune system HIV, human immuno-deficiency virus) is the virus that causes AIDS