1. Disease Disease Communicable Disease – Communicable Disease – Pathogen Pathogen is an illness. - An illness caused by a pathogen. is a disease carrying is a disease carrying organism. organism. Passed from one person to another

2. Disease Carrying Pathogens Disease Carrying Pathogens 1. Viruses A. Programmed to infect only certain body cells B. Directs infected cell to produce more viruses C. E.G. – common cold, measles, chickenpox, and influenza.

3. 2. Bacteria A. Single-celled microorganisms B. In excess of 1000 types of bacteria of which only about 100 cause diseases C. E.G. – strep throat, tuburculocis (TB), E.coli, pnuemonia, and Lyme disease.

4. 3. Rickettsia A. Grow inside living cells and resemble bacteria B. Much smaller than bacteria C. E.G. – Rocky Mountain spotted fever and typhus

5. 4.Fungi A. Single-celled or multicelled plantlike organisms, such as yeast and molds B. Cause diseases of the skin, mucous membranes, and the lungs C. E.G. – athletes foot, ringworm, jock itch, and nail infections

6. 5. Protozoa 1. Tiny, single celled parasites 2. E.G. – malaria, disentery

7. Skin – unbroken skin prevents pathogens from entering the body. Skin – unbroken skin prevents pathogens from entering the body. Tears, Saliva, and Perspiration – contain chemicals that kill pathogens. Tears, Saliva, and Perspiration – contain chemicals that kill pathogens. Mucous Membranes – secrete mucous that trap and destroy pathogens Mucous Membranes – secrete mucous that trap and destroy pathogens Stomach Acids – when pathogens are swallowed they are killed by stomach acids. Stomach Acids – when pathogens are swallowed they are killed by stomach acids.

8. Fever – the higher temperature is an unfavorable environment for many pathogens to live. Fever – the higher temperature is an unfavorable environment for many pathogens to live. Immune system response Immune system response T cells – WBC that regulate the action of the immune system T cells – WBC that regulate the action of the immune system Phagocytes – WBC that surround and kill pathogens by ingesting Phagocytes – WBC that surround and kill pathogens by ingesting B cells – cells that produce antibodies (proteins that help fight infection) B cells – cells that produce antibodies (proteins that help fight infection)

9. Active immunity – antibody resistance from vaccines Active immunity – antibody resistance from vaccines Passive immunity – antibodies from blood transfusion defend against pathogens – short term – only when development of disease in imminent Passive immunity – antibodies from blood transfusion defend against pathogens – short term – only when development of disease in imminent