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MU - MBI 111 - Class Notes - Week 3

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background image Historical Impact of Infectious Disease on Human Societies (pt.1) MBI 111 I. City Living & Disease (10,000 yrs ago)
a.
large numbers of hosts and live close together b. sanitation problems (garbage, sewage, lack of clean water sources) c. animals live in close proximity—rat­infested ships d. Plague brought to the U.S. through port of San Francisco in early 1900s. II. Infectious Diseases Become Endemic a. Invading microbes often lead to an  infection (where pathogenic microorganism  penetrate the host’s defenses, enter the tissues, & multiply). When all of the 
effects of the infection damage/disrupt tissues and/or organs, the 
pathologic state  that results is called a  disease (defined as any deviation from health). Infectious  disease: disruption of a tissue or organ caused by microbes & their products b. Best scenario for infectious agents: infect, multiply, release from host without 
killing them
c. Contamination without colonization and colonization without disease­­RULE d. Best scenario for host: survive in microbial world i. Immune system would build up against diseases e. Gradual genetic changes (thanks evolution) lead to host populations adapting to 
infectious agents and agents adapting to host populations
i. Diseases most of the time become  endemic in a specific population III. Local Endemic Diseases & Travelers a. If an infectious agent exists at an endemic level, it is constantly active in the 
population
b. Travelling to a new region came with a high risk of acquiring new diseases 
endemic to that region
i. Those travelers would also bring new diseases with them IV. Leprosy & Plague a. Two significant diseases of ancient times: i. Leprosy: skin & nerve disease cause by  Mycobacterium leprae  bacteria ii. Tuberculoid Leprosy: shallow & irregular skin lesions. Can lose some 
sensation due to the nerve damage in affected areas
iii. Leptromatous Leprosy: disfiguring, significant damage to nerves occur 
which may lead to more serious unrecognized injuries
b. Ancient leprosy: i. Term “leprosy” may have included other skin disease besides actual 
leprosy
c. Long term impact of leprosy (ideas originating possible after disease surfaced) i. Diseases can be  contagious ii. Isolation can be used as prevention
background image 1. Leprosy not that contagious iii. Leprosy now called Hansen’s Disease d. Plague: complex disease which can affect multiple organs caused by  Yersinia  pestis  bacteria. Y. pestis carries genes that help it to cause disease in mice & to  survive in the flea vector. Three forms: i. Bubonic Plague: Yersinia pesits transmitted from ratshumans by rat flea
bites
1. lymph nodes become infected & swell (“bubos”), and become 
necrotic (tissue death)
2. fever, chills, headache [fatality rate= 15%] 3. BOOK: bacterium injected by bite of a flea, enters the lymph and 
is then filtered by a local lymph node. Infection causes 
inflammation and necrosis of the node, resulting in a swollen 
lesion, or a 
bubo.  a. Incubate period lasts 2 to 8 days ii. Septicemic “Black” Plague: occurs when Yersinia pestis spread from 
lymph nodes to bloodstream. Immune system provides excessive reaction 
to endotoxin of bacteria 1. Result is intravascular coagulation a. Clotted capillaries b. Blood pools under skin c. Tissue death, blackened  2. Death occurs by septic shock [fatality rate = 100% (30­50% w/ 
treatment)]
3. BOOK: presence of the bacteria in the blood results in 
disseminated intravascular coagulation (small blood clots 
developing, blocking small blood vessels, depleting platelets & 
clotting factors needed to control bleeding=excessive bleeding), 
subcutaneous hemorrhage (bleeding under the skin), & purpura 
that may turn into necrosis & gangrene iii. Pneumonic Plague: when Y. pestis spread from the bloodstream of the 
host to the lungs or when the lungs become infected directly by airborne 
transmission  1. Pneumonia (inflammation of the lungs) then occurs leading to 
fatal respiratory failure
2. Death may also occur from septic shock a. Fatality rate = 100% 3. This type disease outbreak results in rapid spread of Y. pestis from 
host­to­host by airborne transmission
a. Rats are not the only cause for outbreak, there have been 
cases of pneumonic plague in the population

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School: Miami University
Department: Microbiology
Course: MBI 111
Professor: Josephcarlin
Term: Spring 2019
Tags: Microbiology, Human, disease, smallpox, plague, leprosy, syphilis, and Introduction
Name: Class Notes Week 3: Historical Impact of Infectious Disease on Human Societies
Description: These notes will cover the second week of material including: history of infectious diseases, leprosy, plague, syphilis, and smallpox. Includes class slides & book notes. Will be on exam 1.
Uploaded: 02/06/2019
6 Pages 72 Views 57 Unlocks
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School: Miami University
Department: Microbiology
Course: MBI 111
Professor: Josephcarlin
Term: Spring 2019
Tags: Microbiology, Human, disease, smallpox, plague, leprosy, syphilis, and Introduction
Name: Class Notes Week 3: Historical Impact of Infectious Disease on Human Societies
Description: These notes will cover the second week of material including: history of infectious diseases, leprosy, plague, syphilis, and smallpox. Includes class slides & book notes. Will be on exam 1.
Uploaded: 02/06/2019