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Questions and Answers
What defines a pandemic in terms of its geographical impact?
What defines a pandemic in terms of its geographical impact?
Which of the following correctly describes a point-source outbreak?
Which of the following correctly describes a point-source outbreak?
Which term best describes an epidemic that affects a specific geographic region at a constant, low level?
Which term best describes an epidemic that affects a specific geographic region at a constant, low level?
How can epidemic patterns be visualized for analysis?
How can epidemic patterns be visualized for analysis?
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Which of the following describes an intermittent common-source outbreak?
Which of the following describes an intermittent common-source outbreak?
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Which factor is NOT typically used to classify epidemic patterns?
Which factor is NOT typically used to classify epidemic patterns?
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In a continuous common-source outbreak, how does the epidemic curve typically appear?
In a continuous common-source outbreak, how does the epidemic curve typically appear?
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What characterizes epidemic outbreaks that are defined as sporadic?
What characterizes epidemic outbreaks that are defined as sporadic?
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What is a characteristic of a propagated source outbreak?
What is a characteristic of a propagated source outbreak?
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In terms of incidence, which of the following statements is correct?
In terms of incidence, which of the following statements is correct?
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How can a vehicle-borne transmission occur in a propagated epidemic?
How can a vehicle-borne transmission occur in a propagated epidemic?
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What distinguishes a common-source outbreak from a propagated outbreak?
What distinguishes a common-source outbreak from a propagated outbreak?
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What is the primary transmission mechanism identified by John Snow in the Broad Street cholera epidemic?
What is the primary transmission mechanism identified by John Snow in the Broad Street cholera epidemic?
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Which of the following factors can affect the susceptibility of a host during an epidemic?
Which of the following factors can affect the susceptibility of a host during an epidemic?
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Which of the following factors is considered when identifying a susceptible host in epidemiology?
Which of the following factors is considered when identifying a susceptible host in epidemiology?
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Which transmission mechanism is specifically referred to in the propagation of the Ebola virus?
Which transmission mechanism is specifically referred to in the propagation of the Ebola virus?
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How did John Snow demonstrate the inoculation of cholera in susceptible hosts during the outbreak?
How did John Snow demonstrate the inoculation of cholera in susceptible hosts during the outbreak?
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What is the primary measure indicated by prevalence rates?
What is the primary measure indicated by prevalence rates?
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Which classification category would the Broad Street cholera epidemic fall under?
Which classification category would the Broad Street cholera epidemic fall under?
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What defines a continuous common-source outbreak?
What defines a continuous common-source outbreak?
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In the context of the epidemiologic triangle, which component is represented by the River Thames in the cholera outbreak?
In the context of the epidemiologic triangle, which component is represented by the River Thames in the cholera outbreak?
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What is the significance of the removal of the pump handle in Snow's investigation?
What is the significance of the removal of the pump handle in Snow's investigation?
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Which of the following does NOT belong to the categories of epidemic patterns?
Which of the following does NOT belong to the categories of epidemic patterns?
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What is the primary objective of epidemiologists when studying disease spread?
What is the primary objective of epidemiologists when studying disease spread?
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Study Notes
Public Health & Preventive Medicine (PMBc303)
- Course: Public Health & Preventive Medicine
- Course code: PMBc303
- Academic year: 2024/2025
- Professor: Reham Elkased
Lecture 2: Introduction to Epidemiology
- Topic: Health
- Topic: Public health
- Topic: Epidemiology
Epidemiology: The Science of Disease
- Definition: A branch of public health that studies disease and its spread in populations (human and non-human). Its aim is to limit pathogens and other negative health issues.
- Greek Origin: Epi - upon, demos - people, ology - study
- Epidemiologists: Often called "Disease Detectives," they investigate the cause of disease, identify those at risk, and find ways to stop its spread and prevent future occurrences.
Pioneers of Epidemiology: John Snow
- 1854 Broad Street Cholera Epidemic: Snow observed that cholera was spread by contaminated water from the River Thames, downstream from London.
- Fecal-oral route of transmission: Water contaminated with sewage and human waste.
- Water pump investigation: he mapped cholera cases and linked infections to a specific water pump on Broad Street.
- Public health response: Local officials removed the pump handle, controlling the epidemic.
- First known public health response to an epidemic.
Epidemiology Triangle
- Agent: The cause of the disease (e.g., bacteria, virus). Factors include pathogenicity and dose.
- Host: The person who can get the disease. Factors include susceptibility, genetic composition, nutrition, and immunity.
- Environment: The surroundings and external conditions that support disease transmission (e.g., climate, insects, crowding).
- Time: Incubation period and duration of illness; time period from infection to epidemic threshold.
Chain of Infection
- Infectious Agents: Bacteria, Fungi, Parasites, Viruses
- Reservoirs: Sources where these agents live, grow, and reproduce (e.g., humans, animals, environment).
- Portal of Entry: How the agent enters the susceptible host (e.g., respiratory tract).
- Portal of Exit: How the agent leaves the reservoir (e.g., respiratory tract, skin).
- Modes of Transmission: How the agent moves from reservoir to host (e.g., direct contact, airborne, vector-borne).
Human Reservoir: Carriers
- Classifications of carriers:
- Passive carriers (healthy carriers): People who never experience symptoms but can transmit the disease.
- Active carriers: Infected individuals who may or may not show symptoms.
- Incubatory carrier - shed the microorganism during the incubation period
- Convalescent carrier - shed the microorganism after recovery.
- Incubation period: The time between the entry of the microorganism and the onset of symptoms.
- Convalescent period: The time between the end of symptoms and when the microorganism is no longer present.
Levels of Disease
- Endemic: Constant presence or usual prevalence of a disease in a geographic area (e.g., Hepatitis A, schistosomiasis in Egypt).
- Epidemic: Sudden increase in disease cases above the normal expectancy for a geographic area (e.g., SARS in 2003).
- Outbreak: Same as epidemic, but in a more limited geographic region.
- Pandemic: Epidemic that spreads over multiple countries or continents and affects a large number of people (e.g., Spanish Flu, Covid-19).
- Sporadic: Disease that occurs infrequently and without any geographic concentration.
Epidemic Patterns
- Common source: Outbreak from a single source (e.g., contaminated food/water). Subtypes include point source (exposure within a short time), continuous sources (exposure over a prolonged period), and intermittent sources (exposure that is not continuous).
- Propagated source: Direct person-to-person contact, vehicle-borne, or vector-borne outbreaks (e.g., Hepatitis B, Yellow Fever).
Measures of Disease Frequency
- Incidence: Proportion of people who develop a condition during a specific time period(number of new cases divided by the population).
- Prevalence: Proportion of people who have a condition at or during a specific time (number of cases divided by the population).
Additional Topics
- Portal of exit
- Susceptible host
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Description
Dive into the fundamentals of epidemiology with this quiz from PMBc303. Explore the science behind disease spread, the role of epidemiologists, and the historical context provided by pioneers like John Snow. Test your knowledge and understanding of public health and disease prevention strategies.
