KEY CONCEPT Germs cause many diseases in humans.

Diseases caused by germs, such as the E 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

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

Disease-causing agents are called pathogens. What would happen if pathogens were eliminated? We wouldn’t get sick

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”

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

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

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

Parasites are multicellular organisms. grow and feed on a host possibly kill the host Ex: Heart worm Round worm Elephantiasis- mosquitos

Direct contact requires touching an infected individual. Includes: 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 Ex: Lime Disease- ticks Malaria- mosquito West Nile Virus- mosquito Rabies- rabid animal HIV- infected person tick

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

Different pathogens cause common infectious diseases.