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HLTA01 Study Guide


Department
Health Studies
Course Code
HLTB21H3
Professor
Caroline Barakat

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Definitions
Parasites organism that grows, feeds, and is sheltered on or in a different organism and that does not
contribute to the survival of its host
Virus ultimate micro-parasite smaller than bacteria; neither cells not organisms; can only reproduce
within their host
Macro-parasites composed of many cells; cycles through transmission stages (eggs and larvae) which
pass into the external environment
Transmission - movement of a parasite from host to host
Incubation period: interval of time required for development of a disease
Latent period: seemingly inactive period between exposure to an infection and subsequent illness
Parasite virulence: capacity of a parasite to cause disease
Zoonotic infection: animal infections that can be transmitted to humans
R0: Reproductive ratio of disease
Incidence: newly diagnosed cases
Prevalence: combination of new(incidence) and existing cases
Low prevalence=low herd immunity
Virulence: how quickly and severe a case can be
What are the main factors that influence the occurrence of a disease?
Host: immunity, genetics, nutrition e.g. person
Agent: Biological, physical, chemical. Psychosocial, rate of growth, persistence e.g. bacterium
Environment: promotes exposure e.g. contaminated water
Modes of Disease Transmission
- Direct transmission - from person to person
- Indirect through a common route / vector, e.g. contaminated air / water, mosquito
Portal of entry:
-Dermal through the skin, e.g. fungus
-Ingestion through the mouth, e.g. E.coli in water
-Inhalation during respiration, e.g. particulate matter
-Aspiration airway entry
Types of diseases
Broad spectrum of disease severity Iceberg concept
Subclinical disease
Exposure without infection
Infection without clinical illness(asymptomatic infection)
Clinical disease
Moderate severity mild illness
Classical & severe disease
Class A: inapparent infection frequent
Tuberculosis infectious disease that most commonly attacks the lungs
Class B: Clinical disease frequent; few deaths
Measles common skin rash, transmitted from respiration
Class C: Infections usually fatal
Rabies affects central nervous system, transmitted through saliva
Types of disease outbreaks
Three main types
1)Endemic usual occurrence of a disease within a given geographical area
2)Epidemic occurrence of a disease in excess of normal expectancy
3)Pandemic worldwide epidemic
Determinants of disease outbreaks:
Herd immunity resistance of a group to an disease attack due to immunity
-For measles estimate that 94% of the population must be immune
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Incubation period
Attack rate ratio of the #people in whom a certain illness develops / total #people at risk
Definition of Plagues
Legionnaires Disease - 1976
Peter turner, Philadelphia
Fatality rate: 15%
Toxic shock syndrome (traced to 1979)
Death rate: 4%, gendered, not STD
Median age: 22
S.aureus, Mary Benton UCLA
SARS(severe acute respiratory syndrome)
64yr old chinese physician, HK, Feb2003
Typhoid Fever
Mary Mallon, 1906
Irish immigrant to US
Carrier of Salmonella enterica aka Typhi
Type 1 Epidemic
Require big population
Regular series of peaks
Disease never completely disappears
R0 greater than 1
Type 2 Epidemic
Medium pop.
Peaks are discontinuous
Regular occurrence of cases
R0 less than 1
No endemicity
Temp. absences of the disease
Type 3: small pop.
Long period with no disease
Cases occur at irregular intervals
R0 much smaller than 1
Immunization
Measles: 95% Mumps: 90% Rubella:85%
R0: 50-100 require 99%
Measles: dogs, Rinderpest: cattle, Smallpox: cow,
Poxvirus: pigs&fowl, human TB related to bovine TB, HIV:chimps, SARS: civet cats
Mosquitoes and flies are vectors of Malaria, yellow fever and African sleeping disease
Disease that would affect Hunter gatherers: high transmission rates, macroparasites w/o vectos or STDs
In 8000BC human pop settled in villages
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Six Plagues of Antiquity
Predominant diseases during hunter-gatherer society
Move to agriculture and the emergence of epidemic diseases
Emergence of cities - urban life
Plagues of Antiquity
5000 BC to 700 AD
Characterised by parasites with long lived transmission stages
Person to person contact.
The Pharaohs Plague
1900 BC
Nile Valley of Egypt Agriculture and irrigation
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Snail fever or blood fluke disease / endemic hematuria(blood urine) / schistosomiasis
Transmission stages: Sporocysts: larval stages. Ceraria: tailed larva. Miracidia: ciliated larvae
1799 1801 Europeans invade Egypt
Currently, 1 million deaths annually
Schistosoma haematobium(bladder), Africa
S.Japonicum(eggs without spine), Asia
S. mansoni(spine on its side) Liver, America
Adult worm can live to 20-30yrs
The Plague of Athens
430 BC
Route: Ethiopia, into Egypt, then Athens
Athenians defeated, 404BC
High death rates including ``Pericles``
Identity of this plague - unknown to this day
Greek colonies: Ionia
1200BC-750BC: Dark ages
The Roman Fever
Roman Empire established in 27 BC
Malaria became prevalent , Europe from Africa
Thought to result from the bad air
Epidemics every 5 to 8 years
Reduced life expectancy to 20 from 40-50
Targeted children, no immunity
Recurrent fevers on 3rd day(benign tertian) Plasmodium Vivax
`` `` on 4th day (quartan) P. malariae
Enlarged spleens
The Antonine plague
AD 166, the Huns(Mongolia) brought infection
Route: Mesopotamia, into Roman Empire - Europe
Symptoms: pustules on skin after 9 days
Identity of the plague not known likely to be the first record of smallpox
Return in AD 189 (2000deatday) less widespread
Emperor Marcus Aurelius Antoninus died May 17 AD180 command repel invasion by Parthian
The Cyprian plague
250 AD contagious from persons
Originated in Ethiopia, moved to Egypt, then to the Roman colonies of North Africa.
Pandemic, lasted 16 yrs.
4 horsemen of the Apocalypse: disease, famine, war and death
Gangrene on hands n`feet
Justinian plague
First pandemic of the Bubonic plague
Arrived in 541 in Constantine (5yrs later reach Ireland)
Raged Europe, North Africa and the Middle East until 757
1 million people died in 5 years period
By 600 AD, mortality at 100 M in western Europe
Recurred every 3 or 4 yrs
Impacts
Quarantine
Pest houses
Quick burials
Burning of clothes and bedding
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