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Infectious Disease 40-1 Organs of the immune system Why do you get sick? • 3 causes of disease: – 1. agents (pathogens) – 2. environment: cigarette smoke – 3. inherited genes: hemophilia, sickle cell anemia Germ theory of disease • L. Pasteur and R. Koch( 1850s) • Germ theory: infectious diseases are caused by microorganisms, called germs Louis Pasteur Koch’s postulates • Pathogen will always be found in the sick, not in the healthy • It must be isolated and grown as a culture • If placed in a new host, they will become infected • The pathogen taken from the 2nd host will be identical to the original Lyme disease • Isolated in 1975 in Lyme, Conn. • Symptoms: rash, joint inflammation • The disease is caused by a bacteria, the vector is a deer tick. Vector: animal that carries pathogens from person to person Disease pathogens • Viruses: tiny particles (not living) that invade cells. Takes over the cell’s functions Virus: influenza • Bacteria: cause disease by releasing toxins or by breaking down tissues for food Bacteria: E coli (dysentery) • Protists • Spread by water or vectors. Causes malaria Protist: plasmodium (malaria) • Worms • Flatworms and roundworms can be parasites, causing diseases Flatworm: sleeping sickness Fungi • Infects skin, causing athlete’s foot and ringworm Fungus: athlete’s foot How diseases are spread • Physical contact: touching an infected surface, then touching your mouth, nose, or eyes, or inhaling airborne particles • Contaminated food and water : salmonella, E coli • Infected animals: mosquitoes (vectors) carry West Nile virus, rabies Mosquitoes can inject diseases when they bite Fighting infectious diseases • Antibiotics: kill bacterial infections ONLY • Few viral medicines exist • OTC medicines: relieve the symptoms, not a cure • Your immune system becomes activated and launches an immune response. Today’s topic was…………… I already knew about…………. I just learned that…………….. I’m interested in……………..