Study Guide for Midterm

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HLTA01 Notes I
Chapter 1: The Nature of Plagues
Legionaries Disease 1976 - Turner
- in the lobby of the Bellevue-Stratford Hotel
- bacteria: Legionella in aerosolized water
- symptoms: high fever, chills, headache, muscle aches, dry cough, chest pains, shortness
of breath, vomiting, and diarrhea
- death: lungs filled with fluid and pus, confusion, disorientation, hallucinations and loss of
Toxic Shock Syndrome 1979 ± Mary Benton
- isolated to females, tampons cross linked with carboxymethyl cellulose w/ polyester foam
- bacteria: Staphylococcus aureas
- symptoms: nausea, chills, diarrhea, headache, sore throat, brownish discharge pelvic
- death: multi-organ failure, low blood pressure, hepatitis, renal insufficiency, internal
blood clots
SARS (severe acute respiratory syndrome) 2003 ± Chinese Physician
- in Hong Kong, virus
- symptoms: fever, dry cough, sore throat, headache
- death: respiratory failure
Transmission ± the movement of parasite from host to host (direct or indirect - vectors)
Vector ± animate intermediaries ex: flies, mosquitoes, fleas, ticks etc.
- Transmission by vector ± mechanical(the bite wound of a mosquitoes) or developmental
(parasites that grow in snails or mosquitoes)
Parasite ± obtain resources needed for their growth and reproduction, parasite may harm host,
but may not outright kill them [ex: malaria parasite, red blood cell killer, white blood cell
killer (HIV)]
Micro parasite: 1600 microscope
Prokaryotes ± 1-5 um in size, free living or parasitic
o Bacteria ±spherical (coccus), rod shaped (bacillus), corkscrew (spirillum or
Protozoa ± 5-15 um in size, one-celled eukaryotes, can lead an independent existence (in
water) or be parasitic
Virus ± smaller than bacteria, must be in living cell to reproduce, neither cell nor
Macro Parasite: do not require microscope to see
- composed of many cells [ex: flatworm, roundworm, tapeworm, mosquitoes, flies, lice]
- usually do not multiple within an infected host (except in larvae stages in an intermediate
hosts) instead, produce infective stages that usually pass out of the body of one host
before transmission to another
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Plagues and Parasites
Incubation Period ± the period in which the disease is not active
Carriers ± infectious but asymptomatic individuals, can infect others but do not
experience symptoms themselves
- requires a infectious individual, susceptible individual and means of transmission
Plague - Epidemic ± the sudden increase in the number of people in a population infected by a
disease, disease outbreak
Epidemiologists ± disease forecasters
Mutiplier R ± predicts how fast a disease will spread thru the population
R is the number of touch taggers that UHVXOWVIURPWKHLUEHLQJLQFRQWDFWZLWKµLW
R > 1 the seeds of transmission will lead to an ever expanding spread of disease (plague)
R < 1 each infection produces fewer than one transmission stage and parasite cannot
establish itself
Parasite Virulence ± how strong is it? higher virulence require more population to survive, less
virulence can survive in a smaller population
Epidemic Types
Type I ± ENDEMIC - population is large and the pattern shows a regular series of
outbreaks (peaks), never completely disappears and cases persist (R > 1)
Type II ± NO ENDEMICTY - peaks are discontinuous but there is a regular pattern of
occurrences of cases, there are temporary absents of disease because of not
enough people to infect (R < 1)
Type III ± irregular outbreaks with long fadeouts occurring between peaks (R very < 1)
Pandemic ± when an infectious disease becomes worldwide or widespread
Factors affecting spread of disease
- size of population
- communal activities that bring susceptible individuals in contact with infectious
- countermeasures used (ex: quarantine, hospitalization)
- Seasonal Patterns (temperatures)
Reducing number of Susceptibility
- immunization, sociological changes, quarantine
Herd Immunity ± reduce the number of susceptible individuals below a critical point
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Benign Evolution ± Over time virulent parasites may become benign, coexistence with host
- although parasite virulence tends to decline over evolutionary time it never becomes
entirely benign
Pathogenic ± causing disease
- how severe or how pathogenic the disease will be, is determined by two components:
virulence and host resistance
Parasite survival requires:
- reaching and infecting new hosts, effective dispersal mechanisms
- the victorious parasite is the one that most ruthlessly exploits the pool of resources (food)
provided by the host and produces more offspring
Reducing Virulence
- clean water, clean needle exchange, and condom use, immunization
Chapter 2: Plagues, the Price of Being Sedentary
Zoonoses/Zoonotic Infections ± animal infections transmitted to humans
Hunter-Gathers ± small groups, human to human transmission were absent
3 surges to human population:
1) Tool-Making Revolution: killing meat
2) Agriculture Revolution: change from hunter-gather to farming, irrigation, human waste as
fertilizer, politics, banking, urbanization(city building), domestication of animals
3) Scientific-Industrial Revolution:
Impact of Disease
- population density
- character and quality of the water supply, food and shelter
- frequency of contact among individuals
- human contact with animals (big 5 ± sheep, goat, pigs, cows, horses)
- climate
- ³DFFLGHQWRIJHRJUDSK\´± different plants and animals available in different areas
- Measles ± dogs and cattle
- Smallpox ± cows, pigs and fowl
- Tuberculosis ± bovine TB
- HIV ± chimpanzees
- SARS ± civet cats
- hematuria - snails
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