GPH 380E Foundations of Biostatistics and Epidemiology - Lecture 2

A set of practice flashcards covering core epidemiology concepts from Lecture 2, in a QUESTION_AND_ANSWER format.

What is epidemiology, in one concise definition?

The study of how diseases or health characteristics are distributed in populations and the factors that influence or determine that distribution.

What are the three broad categories of factors that influence disease distribution according to the notes?

Biological, Environmental, and Behavioral factors.

List the five main objectives of epidemiology.

1) Identify etiology (cause and risk factors) 2) Determine the extent of the disease (burden in the community) 3) Study the natural history and prognosis of the disease 4) Evaluate prevention and therapeutic measures and health-care delivery 5) Provide the foundation for developing public policy on environmental, genetic, and social/behavioral aspects of disease prevention and health promotion.

What does the term ‘epidemiologic transition’ refer to?

The shift in disease patterns over time from infectious/communicable diseases to chronic noncommunicable diseases as population conditions change.

Name at least four factors contributing to the re-emergence of infectious diseases mentioned in the notes.

Antibiotic resistance, globalization/increased travel, climate change, and vaccine hesitancy.

What is the difference between a population-based preventive approach and a high-risk preventive approach?

Population-based: preventive measures applied to the entire population. High-risk: preventive measures targeted only to high-risk groups.

How does epidemiology contribute to clinical decision-making, according to the notes?

By using population data to inform diagnosis and management; for example, correlating clinical findings with pathology results from large groups.

Name three historical epidemiology-driven figures highlighted in the notes.

John Snow (cholera), Ignaz Semmelweis (handwashing), and Edward Jenner (vaccination).

What are the components of the Triad of Disease?

Agent, Host, Vector, and Environment.

List the primary modes of transmission described.

Direct transmission (person-to-person), Indirect transmission (common vehicle, single exposure, multiple exposures, continuous exposure), and Vector transmission.

Explain the Iceberg Concept in epidemiology.

Most disease cases are subclinical or not clinically apparent; only a small portion are visible (the tip of the iceberg). Subclinical cases can still transmit disease.

What are endemic, epidemic, and pandemic definitions?

Endemic: disease habitually present at a stable level in a region. Epidemic: sudden increase in cases in a community beyond expected levels. Pandemic: a worldwide epidemic affecting many countries.

What is incubation period in infectious diseases?

The time between exposure to an infectious agent and the onset of symptoms.

What is the difference between preclinical, subclinical, persistent, and latent disease states?

Preclinical: disease not yet clinically apparent. Subclinical: disease not clinically apparent and not destined to become apparent. Persistent: infection persists for years. Latent: infection with no active multiplication of the agent.

Define carrier status in epidemiology.

An individual harbors a pathogen but shows no clinical illness and often no serologic evidence, yet can transmit the infection.

Who was Typhoid Mary and why is she notable in epidemiology?

Mary Mallon, a healthy carrier of Salmonella typhi who caused multiple typhoid outbreaks; she highlighted the concept of asymptomatic carriers.

What is herd immunity and why is it important?

The resistance of a population to disease due to high levels of immunity, which reduces transmission and protects unvaccinated individuals; it depends on a disease-specific threshold.

What is the approximate herd immunity threshold for measles based on the notes?

About 91–94% immune.

How do you calculate the attack rate in an exposed group?

Attack Rate = (Number of people at risk who develop illness) / (Total number of people at risk in the group). The food-specific attack rate applies the numerator and denominator to those who ate the food.

Define the secondary attack rate (SAR).

SAR = (New cases among contacts of a primary case) / (Total number of susceptible contacts).

What are the key questions in an outbreak investigation?

Who is affected? When did it occur (temporal pattern)? Where are cases clustered (geography)?

What is cross-tabulation used for in epidemiology?

To determine which exposures are associated with an outbreak by comparing exposure groups and their illness rates.

In the Dade County Jail outbreak, what did cross-tabulation help identify?

It helped compare exposures (e.g., beverages and egg salad) and their associated attack rates to identify likely sources of illness.

What is the significance of geographic clustering in disease epidemiology?

Cases are not randomly distributed in space; clustering helps identify where transmission is concentrated and directs control measures.

Give two examples of climate- or environment-related factors contributing to re-emergent infectious diseases.

Rising temperatures expanding habitats of vectors (e.g., mosquitoes for malaria, dengue, Zika) and environmental degradation increasing exposure to pathogens.

What are the “Two Approaches to Prevention” mentioned, and an example of each?

Population-based approach (e.g., broad dietary advice to reduce coronary disease) and High-risk approach (e.g., cholesterol screening focused on high-risk children).

What is the role of surveillance in addressing subclinical disease?

Public health surveillance and testing are needed because subclinical cases contribute to transmission and are not captured by clinical case counts.

What factors influence whether a disease shows a local, national, or global pattern (place, time, and person)?

Place (geographic clustering), Time (seasonal/annual trends), Person (age, sex, behavior, genetics) — the core questions in disease occurrence.

What is the significance of the relationship between dental caries and fluoride content in water as an example of epidemiologic methods?

It illustrates how ecological data and environmental factors (fluoride levels) relate to disease outcomes (caries rates) across communities.

What major point about disease causation is highlighted by epidemiologic reasoning in the notes?

An observed statistical association between exposure and disease does not automatically imply causation; causal inferences require careful analysis of patterns.