Bio171-F08-lec38 - Biology 171 Lecture 38 Friday December 5...

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Lecture 38: Friday December 5, 2008 Biology 171 Today’s Topic: Emerging Infectious Diseases Announcements Course Evaluations online Final Exam Tues. Dec 16 7-9PM – covers lectures 30-39 & last 3 discussions Review Sun. Dec 14 4-6PM - 1800 Chem Human Disease: Transmission Modes Human‐Human – tuberculosis, HIV/AIDS Water‐borne ‐ cholera Vector‐borne diseases human only – dengue fever zoonotic diseases: West Nile fever, Lyme disease Text Reading Lec. 38: none Lec. 39: none
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The phrase ‘emerging infectious diseases’ was coined by Nobel Prize winner Joshua Lederberg. It is applied to infections that newly appear in a population, or have existed but are increasing in incidence or geographic range. Throughout history, disease causing pathogens and parasites have acted as selective pressures on human populations. In 14 th century Europe, plague, caused by the bacterium Yersinia pestis , and transmitted by fleas, killed one‐third of the population. Yersinia pestis Rat flea, Xenopsylla cheopis
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The field of Epidemiology is the study of disease transmission through human populations. Human diseases are transmitted via several modes: 1. Directly from person to person 2. Via inanimate objects (e.g. food or water) 3. Via animal vectors
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Reservoirs of disease An Anthroponosis is a disease that affects only humans e.g. smallpox, malaria A Zoonosis is a disease that has animal reservoirs e.g. Lyme disease, Ebola hemorrhagic fever
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Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis that affects mainly humans (animal reservoirs are rare) . Throughout history, tuberculosis has killed millions of people. TB kills between 2 and 3 million people each year and is the leading cause of death among young adults and a major cause of death among women of childbearing age. Tuberculosis
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Perhaps the most alarming aspect of the present epidemic is the rise in multidrug‐resistant TB (MDR‐TB). According to a survey conducted by the WHO, up to four percent of all TB cases worldwide are resistant to more than one anti‐tuberculosis drug. In parts of Eastern Europe, nearly half of all TB cases resist at least one first‐line drug. Most of the burden of MDR‐TB falls on poor countries, but the United States has seen outbreaks of drug‐ resistant TB as well. In early 1990s, New York City had an epidemic of MDR‐TB that cost almost $1 billion to control. (NIH, 2005) Tuberculosis
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Why is tuberculosis an emerging disease? Encapsulated bacteria are difficult to kill, leading to many people not completing antibiotic treatments. This selects for resistant strains. Many cases are asymptomatic. Crowded conditions foster spread. Immune‐compromised people are at particular risk. Tuberculosis
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AIDS (Acquired Immune Deficiency Syndrome) was first described in 1981. The virus now known as HIV (Human Immunodeficiency Virus) was first characterized in 1983. Evidence of the virus was recovered from tissue samples from a Congolese man taken in 1959, the oldest known record of the virus in humans.
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