InfectiousDisease Final

InfectiousDisease Final - Infectious Disease Infectious...

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Infectious Disease
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The most dangerous of enemies that vertebrates have ever faced aren't lions, tigers, or bears, but rather, microscopic organisms called microbes . Microbes have caused diseases throughout history that have decimated human populations. The Black Death in the 1300s killed 25 million Europeans, nearly 50% of the population. More recently, the Spanish Flu from 1918-1920 killed 25-50 million people. Microbes include bacteria, viruses, protozoa and fungi and, until recently, they have been the leading cause of death among humanity (see figure 1). Even today nearly 30% of all deaths worldwide can be attributed to an infectious disease . The top three infectious disease killers include HIV/AIDS, tuberculosis, and malaria caused by a virus, bacteria and protozoa respectively. The connection between microbes and disease is called “germ theory” and although this seems obvious to us today, it was very controversial when first proposed. Throughout most of history it was thought that disease was spontaneously generated and even as late as the mid-1800s the prevailing theory was the “miasma theory” of disease. A miasma was believed to be a poisonous vapor filled with particles of decomposed matter that could cause disease. It took contributions from many scientists to slowly overturn these ideas, however two Infectious Disease Figure 1: Not all microbial species are pathogenic, but many do cause disease.
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Figure 3 Microbial Diseases Figure 2 Fathers of Microbiology of the most famous include Louis Pasteur (from which the word pasteurization comes) and Robert Koch (see figure 2). Pasteur's experiments confirmed the germ theory of disease and played a major role in convincing the rest of Europe as well. His ideas led Joseph Lister to develop and champion sterile technique during surgery. Keep in mind that before this, surgeons did not even wash their hands or surgical tools before operating and while a patient might survive the surgery, many died of post-operative infections. Robert Koch established “Koch's postulates” which are a series of proofs used to verify that a specific microbe causes a specific disease. This was important because although Pasteur had convincingly shown that “germs” cause disease, no one had ever demonstrated which “germ” caused which disease. In 1875, Koch used his postulates to successfully demonstrate that anthrax was caused by the bacterium Bacillus anthracis. The germ theory laid the foundation for the development and use of antibiotics, vaccines, hygienic practices and public sanitation. Practices that we take for granted today. All microbes have the same basic goal --to survive and reproduce. How they actually accomplish this varies from organism to organisms so let's look more closely at some similarities and differences between bacteria, viruses, protozoa and fungi and some of the disease they can cause if they are able to survive and reproduce within your body (see figure 3). Bacteria
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This note was uploaded on 04/21/2008 for the course BIOL 100 taught by Professor Lee during the Winter '07 term at San Diego State.

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InfectiousDisease Final - Infectious Disease Infectious...

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