Epidemiology Basics Quiz

Epidemiology in Community Health Care

• Epidemiology is the science that examines the distribution and determinants of health-related states or events in specified populations.
• It bridges biomedical, social, and behavioral sciences.

Historical Roots of Epidemiology

• Ancient Times: Hippocrates (460-375 BCE)
• Middle Ages: 1348 Plague (Black Death)
• 18th Century: Florence Nightingale (1820-1910).
• 19th Century: Causal thinking, Sanitary statistics, Infectious-disease epidemiology, Chronic-disease epidemiology.
• Current: Eco-epidemiology

Classically Speaking

• Epi = upon
• Demos = people
• Ology = science
• Epidemiology is the science of what falls upon people.

A Modern Definition

• Study of occurrence and distribution of health-related diseases or events in specified populations, including the study of influencing determinants and applying knowledge to control health problems.

Terms to Know

• Disease: A pattern of response to invasion or injury, leading to alterations in organism functioning.
• Pathogens: Organisms or substances (e.g., bacteria, viruses, parasites) capable of causing disease.
• Pathogenesis: The development, production, or process of generating a disease.
• Pathogenic: Disease-causing.
• Pathogenicity: The potential ability and strength of a pathogenic substance to cause disease.
• Toxins: Poisonous substances from living organisms, often metabolic products.
• Antibiotics: Substances produced by or derived from microorganisms to inhibit or kill other microorganisms.
• Incidence: The extent that people, within a population not having the disease, develop it during a specific time period.
• Prevalence: The number of people within a population who have a certain disease at a given point in time, including point prevalence.
• Immunity: The host's ability to resist a particular infectious disease-causing agent.
  • Acquired immunity: Resistance to an infection acquired through prior exposure.
  • Nosocomial infection: An infection not present or incubating upon admission to a hospital.
  • Herd immunity: describes the immune level present in a population group.
• Etiology: The factors contributing to the origin and cause of a disease.

Theories of Causality in Health and Illness

• Relationship between a cause and its effect.
• Chain of causation (in noninfectious diseases), incorporating environmental exposure and potential health outcomes (nine elements).
• Multiple causation (Dever's epidemiological model or Web of Causation).

Purposes of Epidemiology

• Investigate nature/extent of health-related phenomena in communities and identify priorities.
• Study the natural history and prognosis of health-related problems.
• Identify causes and risk factors.
• Recommend and evaluate interventions (preventive and therapeutic).
• Provide a basis for public policy.

Uses of Epidemiology

• Study the cause (etiology) of conditions such as diseases and disorders.
• Determine the primary agent and causative factors.
• Determine the characteristics of the agent.
• Define the mode of transmission.
• Identify and define geographic patterns
• Determine, describe, and report on the natural course of disease, disability, injury, and death.
• Aid in the planning and development of health services and programs
• Provide administrative and planning data

Uses of Epidemiology in Disease Control and Prevention

• Identify characteristics of those suffering from diseases.
• Explore differences in location/environment, living conditions, and development
• Determine common time factors of disease acquisition
• Identify factors for risk of developing a disease

Epidemiological Methods

• Descriptive epidemiology: Focuses on the amount or distribution of health problems in populations by describing characteristics of protected/affected groups (person, place, time).
• Factors of Interest: age, sex, ethnicity, socioeconomic status, occupation, family status
• Morbidity and mortality rates help clarify extent and risk factors.

Basic Triad of Descriptive Epidemiology

• Person: Relevant characteristics like age, gender, socioeconomic status.
• Place: Geographic location, environmental factors, etc.
• Time: Time trends and patterns of disease occurrences within a certain time frame.

Personal Characteristics

• Age
• Gender
• Socioeconomic status (education, occupation, income)
• Marital status
• Ethnicity/race/genetic profile
• Behavior/habits

Place

• Geographically restricted or widespread (outbreak, epidemic, pandemic)
• Climate effects (temperature, etc.)
• Urban/suburban/rural, etc. Exposure to environmental factors (water, food supply)
• Multiple clusters or one?

Time

• Changing or stable?
• Clustered (epidemic) or evenly distributed (endemic)?
• Time trends: point source, propagated, seasonal, secular, combinations.

Analytic Epidemiology

• Investigates disease causes.
• Determines reasons behind disease rate differences among populations.
• Evaluates hypotheses using descriptive data.
• Establishes cause-and-effect relationships between preexisting factors, conditions, and diseases.

Phenomena Assessed in Analytic Epidemiology

• Agent: Biological, physical, chemical, environmental, psychological factors.
• Host: Genetic makeup, immunologic status, personal characteristics, personal behavior, etc.
• Environment: Living conditions, climate, resources, etc.

Agents

• Biological (micro-organisms)
• Physical (temperature, radiation, trauma)
• Chemical (acids, alkalis, poisons, tobacco)
• Environmental (nutrients, allergens)
• Psychological experiences

Host Factors

• Genetic endowment
• Immunologic status
• Personal characteristics
• Personal behavior
• Definitive versus intermediate diseases (vector-borne)

Environment

• Living conditions (housing, water, refuse, sewage)
• Climate
• Modes of communication (vector, vehicle, reservoir)

Type of Analytic Epidemiology

• Prevalence studies
• Case-control studies
• Cohort studies
• Experimental epidemiology

Sources of Epidemiologic Information

• Vital statistics
• Census data
• Reportable diseases
• Disease registries
• Environmental monitoring
• National Center for Health Statistics data
• Health surveys
• Informal observational studies
• Scientific studies

Disease Transmission

• Fomites: Inanimate objects (pencils, etc.) that transmit diseases.
• Vectors: Living organisms (like insects or rodents) that transmit diseases.
• Reservoirs: Living organisms, or inanimate matter in which infectious agents live and multiply (food, soil).
• Zoonois: When animals pass diseases to humans.
• Carriers: Individuals who carry a disease without experiencing symptoms.
  • Active carriers: Have recovered, carry the disease.
  • Convalescent carriers: In recovery, still infectious.
  • Healthy carriers: Do not show symptoms, but are contagious.
  • Incubatory carriers: Show symptoms, and are contagious during incubation stage.
  • Intermittent carriers: Can intermittently spread the disease, Show symptoms.
  • Passive carriers: Carry, but have no symptoms or signs of diseases.

Modes of Disease Transmission

• Direct: Person-to-person contact, immediate transfer.
• Indirect: By intermediary such as agents, items, or animals, including
  • Airborne (droplets, dust).
  • Waterborne (water sources.)
  • Vehicleborne (fomites.)
  • Vectorborne (host intermediaries.)

Diseases for which vaccines are used

• Anthrax, Chicken pox, Cholera, Diphtheria, German measles, Hepatitis A & B, Influenza, Malaria, Measles, Meningitis, Mumps, Plague, Pneumonia, Polio, Rabies, Small pox, Spotted fever, Tetanus, Tuberculosis, Typhoid Fever, Typhus, Whooping Cough, Yellow Fever

Risk

• Probability of a disease or unfavorable health condition developing.
• Directly influenced by biology, environment, lifestyle, and healthcare systems.
• Epidemiologists study populations at risk to collect data relating health risks and problems, present or absent factors.
• Measurement of relative risk: Incidence rate in exposed compared to unexposed groups.

Risk Factors

• Variables that increase the rate of disease in individuals and groups.
• Identification is critical for preventing diseases.
• Examples include genetic predisposition, infectious agents, or dietary habits.

Risk Estimates

• Probability of a negative event, observed or calculated within specified time after exposure to particular hazards.
• Examples such as walking in snow (light clothing = risk factor), cold occurrence (risk event)

Risk Rate

• Introduces time factor to frequency of new health event cases, observing each participant's duration of exposure.

Relative Risk

• Reflects increase in disease frequency in one group (exposed) versus another (unexposed).
• Measures strength of association and likelihood of causality.

Methods in Epidemiologic Investigative Process

• Descriptive Epidemiology: Uses counts and rates
• Counts: Absolute numbers of cases
• Rates: Incidence (new cases) and prevalence (existing cases)
• Computing rates: Mortality and Morbidity

Rates

• Statistical measures of proportion of health problems within a population.
• Used to compare occurrences across time and places.

Specific Rates for Maternal and Infant Populations

• Crude birth rate
• General fertility rate
• Maternal mortality rate
• Infant mortality rate
• Perinatal mortality rate

Epidemiologic Research Steps

• Identify the health problem.
• Review existing literature.
• Design the study carefully.
• Collect the data.
• Analyze the findings.
• Develop conclusions and applications.
• Disseminate the findings.

Aggregate Health

• Epidemiology provides methodology to assess health of aggregates.
• Provides framework for improving clinical practice.
• Wellness models may expand to include behavioral aggregates

Use of Epidemiology in Disease Prevention

• Primary Prevention: Measures taken before disease development (e.g., informing people about preventive measures).
• Secondary Prevention: Measures taken after disease’s pathogenesis has occurred (e.g., early diagnostics).
• Tertiary Prevention: Measures taken to limit disability after disease occurrence (e.g., rehabilitation).

Establishing Causality

• Criteria for establishing causality, especially in noninfectious diseases.

Criteria of Establishing Causality

• Strength of association
• Consistency
• Specificity
• Temporality
• Biological gradient
• Plausibility
• Coherence

Additional Information

• Methods in Epidemiological Investigative Process (counts, rates of incidence, prevalence)
• Questions and Answers on Epidemiology concepts: True/False statements to identify important concepts.