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31.1 Pathogens and Human Illness KEY CONCEPT Germs cause many diseases in humans. 31.1 Pathogens and Human Illness • Diseases caused by germs, such as the E. Coli bacteria can be fatal (death) • 1330-1352, the bacteria that caused the “Black Death” or the Plague originated from fleas on rats – Has killed approx. 100 MILLION people – New diseases - HIV SARS Avian Flu (bird flu) Swine Flu 31.1 Pathogens and Human Illness • Germ theory proposes that microorganisms cause diseases. – led to rapid advances in understanding disease – Can be infectious (polio, flu), caused by germs – or noninfectious (cancer, heart disease) caused by genes or lifestyle 31.1 Pathogens and Human Illness • Disease-causing agents are called pathogens. • What would happen if pathogens were eliminated? – We wouldn’t get sick 31.1 Pathogens and Human Illness There are different types of pathogens. • Bacteria are single-celled organisms. – cause illness by destroying cells – release toxic chemicals – – – – Exs: E. Coli Salmonella “Food Poisoning” 31.1 Pathogens and Human Illness • Viruses are disease-causing strands of DNA or RNA that are surrounded by a protein coat. – Take over a healthy cell – Force cells to produce more of the virus – Smaller than bacteria – Exs: – HIV – – – – Influenza Herpes *Common Cold AIDS 31.1 Pathogens and Human Illness • Fungi can be multicellular or single-celled. – take nutrients from host’s cells – occur in warm and damp places Ex: Athlete’s foot, yeast, mold 31.1 Pathogens and Human Illness • Protozoa are single-celled organisms – Prey on other cells – use host cells to complete their life cycles – take nutrients from host cell – Ex: Malaria, dysentery 31.1 Pathogens and Human Illness • Parasites are multicellular organisms. – grow and feed on a host – possibly kill the host Ex: Heart worm Round worm Elephantiasis- mosquitos 31.1 Pathogens and Human Illness • Vectors any person or animal that carries and transmits a pathogen to another living organism. • Direct contact requires touching an infected individual. Includes: – kissing – sexual intercourse – hand shaking – bite tick Ex: Lime Disease- ticks Malaria- mosquito West Nile Virus- mosquito Rabies- rabid animal HIV- infected person 31.1 Pathogens and Human Illness Pathogens can enter the body in different ways. • Direct contact require an infected person or animal to physically touch a healthy person Ex: Rabies, HIV • Indirect contact does not require touching an infected individual. – touching an infected surface – breathing in infected air Ex: SARS Tuberculosis 31.1 Pathogens and Human Illness • Different pathogens cause common infectious diseases.
