Week 2

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What defines a case in epidemiological studies?

A potential source of infection that shows no clinical symptoms.

A person or group with discernible symptoms of a disease.

An individual identified as having a specific disease or condition. (correct)

An agent present without causing any observable illness.

Which statement correctly describes a carrier?

An infected individual without recognizable clinical disease. (correct)

A person with mild symptoms of a transmissible disease.

An animal that cannot transmit diseases to humans.

A person who has recovered from an infectious disease.

What are zoonoses?

Infections transferable from animals and birds to humans. (correct)

Illnesses caused solely by bacterial agents.

Diseases that can be spread through water sources.

Infectious diseases that originate from soil contamination.

Which of the following is NOT a mode of direct transmission?

Infected water supply ingestion. Signup and view all the answers

Which type of reservoir can harbor infectious agents without being alive?

Inanimate objects like soil and contaminated surfaces. Signup and view all the answers

Which disease is an example of one that can be transmitted through direct contact?

AIDS through skin-to-skin contact. Signup and view all the answers

What characterizes indirect transmission of infectious diseases?

Infection spread through vectors like insects. Signup and view all the answers

Which type of agent refers to substances or forces that can initiate or perpetuate a disease process?

Agent factors Signup and view all the answers

Which classification does 'fomite-borne' transmission fall under?

Indirect transmission. Signup and view all the answers

Which classification of agents includes substances such as viruses and bacteria?

Biological agents Signup and view all the answers

What are endogenous chemicals?

Chemicals produced within the human body Signup and view all the answers

Which of the following is considered a host factor that affects disease processes?

Genetic traits Signup and view all the answers

Which of these is not a component of the physical environment?

Social support Signup and view all the answers

What is a potential impact of chemical agents categorized as exogenous?

Toxic exposure from outside sources Signup and view all the answers

Which factor does not typically fall under host characteristics?

Global economic trends Signup and view all the answers

Which classification includes excessive exposure to heat or radiation?

Physical agents Signup and view all the answers

Which of the following is NOT a criterion for a disease to be suitable for screening?

The disease should be negligible or not significant for public health. Signup and view all the answers

What is a primary purpose of screening in healthcare?

To identify individuals likely to have a disease at an early stage. Signup and view all the answers

Which characteristic is crucial for the acceptability of a screening test?

It should minimize discomfort to participants. Signup and view all the answers

What does the repeatability of a screening test refer to?

The consistency of results upon repeated testing. Signup and view all the answers

Which of the following is NOT mentioned as a requirement for a screening test?

The test should be painful to ensure accuracy. Signup and view all the answers

How should the benefits of early detection be compared to its risks in screening?

The benefits should outweigh the risks and costs. Signup and view all the answers

Which statement accurately describes the natural history of a disease in the context of screening?

It includes recognizing the period before the disease becomes apparent. Signup and view all the answers

What is a potential consequence of screening when the expected benefits do not exceed the risks?

Unjustified medical interventions on healthy individuals. Signup and view all the answers

What does the term 'disease control' encompass?

Reducing the incidence and duration of disease. Signup and view all the answers

Which statement best describes the concept of disease eradication?

It signifies the complete termination of all disease transmission globally. Signup and view all the answers

What is the main purpose of screening for diseases?

To search for unrecognized disease or defect rapidly. Signup and view all the answers

What is a distinguishing feature of screening tests compared to periodic health examinations?

They are capable of wide application and are relatively inexpensive. Signup and view all the answers

In disease control, how is the disease agent typically treated?

It is allowed to persist at a manageable level. Signup and view all the answers

Which diseases have been seriously considered as candidates for global eradication?

Polio, measles, and dracunculiasis. Signup and view all the answers

What is an aspect that differentiates primary prevention from secondary prevention in disease control programs?

Primary prevention aims to prevent disease before it occurs. Signup and view all the answers

Which of the following statements about screening tests is accurate?

Screening tests can identify conditions early, requiring less time from physicians. Signup and view all the answers

What is the primary function of cell-mediated immunity in humans?

Rejection of foreign materials and infections Signup and view all the answers

What factor differentiates active immunity from passive immunity?

Duration of protection Signup and view all the answers

What is a critical consequence of severe defects in cell-mediated immunity in infants?

Mortality within the first 6 months Signup and view all the answers

Which statement accurately describes immunoglobulins?

They can be transferred from mother to child Signup and view all the answers

What role do macrophages play in the immune system?

Activation of other immune cells through signals Signup and view all the answers

Which of the following statements correctly describes the protective efficacy of active immunization?

May approach 100% in ideal conditions Signup and view all the answers

What characterizes passive immunity compared to active immunity?

It provides immediate but temporary protection Signup and view all the answers

What is the primary source of normal human Ig?

A pool of at least 1000 donors Signup and view all the answers

What does a sensitivity of 90% indicate regarding a screening test?

90% of diseased individuals will test positive Signup and view all the answers

How is specificity defined in the context of a screening test?

The ability to correctly identify non-diseased individuals Signup and view all the answers

What is the impact of increasing sensitivity on specificity?

Increasing one generally decreases the other Signup and view all the answers

What does the predictive value of a positive test signify?

The probability the disease is present given a positive test result Signup and view all the answers

When is the predictive value of a negative test most accurate?

When specificity is at its highest Signup and view all the answers

What does a test with 90% specificity indicate about false positives?

10% of non-diseased individuals will be incorrectly identified as diseased Signup and view all the answers

In a population with a higher disease prevalence, how does the predictive value of a positive test change?

It becomes more accurate as true positive results increase Signup and view all the answers

What type of result would be considered a false negative?

A diseased individual who tests negative Signup and view all the answers

Study Notes

Concepts of Health and Disease

Webster defines disease as a condition impairing body health, deviating from a healthy state, and altering human body functions.
The simplest definition of disease is the opposite of health—any deviation from normal physical or mental well-being.

Concepts of Causation

Before Louis Pasteur, various theories explained disease causation, including supernatural and humoral theories.
Microbiology discoveries marked a turning point in understanding disease causes.

Germ Theory of Disease

The germ theory gained prominence in the late 19th and early 20th centuries, shifting focus from environmental factors to microbes as the primary disease cause.
The germ theory often describes a one-to-one relationship between an infectious agent and disease.
Current understanding recognizes that diseases are usually caused by multiple factors.

Epidemiological Triad

The germ theory has limitations. Exposure to an infectious agent does not always lead to disease.
Other factors, such as host susceptibility and environmental conditions, are crucial in disease development.
The epidemiological triad considers the agent, host, and environment as key factors in disease causation.
The interaction of these three factors is essential for disease onset.

Agent Factors

Biological agents include viruses, bacteria, fungi, protozoa, and metazoa, exhibiting infectivity, pathogenicity, and virulence.
Nutritional agents include protein, fat, carbohydrates, vitamins, minerals, and water. Imbalances cause nutritional disorders.
Physical agents encompass extreme temperatures, humidity, pressure, radiation, electricity, and sound.
Chemical agents include both endogenous (body-produced) and exogenous (external) substances. Examples include urea, ketones, metals, allergens, fumes, and dust.
Mechanical forces such as friction and crushing injuries can also cause disease.
Social agents such as smoking, poverty, lifestyle choices, and social isolation are also considered factors.

Host Factors

Host factors are characteristics of the person/animal susceptible to infection.
These can include demographic characteristics (age, sex) and biological characteristics (genetics).

Environmental Factors

The physical environment includes air, water, soil, and living conditions.
The biological environment includes other living things.
Psychosocial environments include social, economic, and cultural conditions.

Multifactorial Causation

Advances in medicine showed that diseases of civilization (e.g., cancer, heart disease) are often multifaceted rather than solely caused by single causes.
Various factors including genetic, psychological, behavioral & social elements contribute to diseases.

Web of Causation

The web of causation model describes multiple factors interacting to cause diseases, like chronic illnesses.
The web emphasizes the interconnectedness of predisposing factors in such diseases, not a single cause.
Elimination or control of critical links in the web is often sufficient to control the illness.

Natural History of Disease

Disease development involves a complex interplay among host, agent, and environment.
The natural history of disease describes how a disease progresses over time from pre-pathogenesis to outcomes like recovery, disability, or death.

Prepathogenesis/ Pathogenesis

The pre-pathogenesis phase is the period before disease onset. Factors present in the environment support infectious agent interaction with susceptible hosts
In the pathogenesis phase, the infectious agent enters the host, leading potentially to disease with progression through incubation to early, late stages, possible outcomes like recovery, disability, or death. Disease processes may be modified by intervention.

Risk Factors

Risk factors are attributes or exposures associated with disease development.
Their presence doesn't guarantee disease, but their absence doesn't rule it out.
Identifying risk factors improves disease prevention and intervention strategies.

Spectrum of Disease

The spectrum of disease model shows disease manifestations with severity on a scale, mild to severe.
Subclinical infections exist on one end, and severe, potentially fatal illnesses are on the other.
States of immunity and receptivity affect the expression of disease manifestations

Iceberg of Disease

The iceberg model presents hidden disease cases (i.e., those undiagnosed), alongside observable overt cases.
It highlights the large portion of disease presence that isn't readily apparent in a population.
Detection and control of hidden diseases are important for effective preventive medicine strategies.

Disease Control

Disease control aims to reduce disease incidence, duration, transmission, complications, and financial burden.
Control strategies may focus on preventing disease (primary prevention) or reducing its impact after it occurs (secondary prevention).

Disease Elimination

Elimination of disease interruption focuses on stopping disease transmission within defined regional areas.

Disease Eradication

Eradication aims to eliminate a disease completely from the entire global population by eradicating the infectious agent.
Smallpox is the only disease eradicated till date.

Screening for Diseases

Screening is a method for detecting unrecognized diseases in individuals with no symptoms.
Screening tests are designed to detect conditions in the early stages, while the disease is still reversible.
Criteria for screening include the disease's importance, recognizable latent stage, and an understanding of its natural history.

Test Acceptability, Repeatability, and Validity

Screening tests should be acceptable to the screened population, repeatable in their results, and valid in measuring the target condition.

Evaluation of Screening Tests

Sensitivity, specificity, predictive values of positive and negative tests are used to evaluate screening tests
These measure the tests' accuracy in identifying diseased and non-diseased individuals.

Uses of Screening

Screening detects unrecognised diseases, controls disease spread, helps researchers learn more about a disease’s natural history, and educates the public.

Infection - Definition, Dynamics, and Sources

Infection is the entry and establishment of an infectious agent in the body.
Disease transmission involves a reservoir of infection, transmission methods, and a susceptible host.
Reservoirs of infection can be humans, animals, or nonliving objects like soil.

Modes of Transmission

Infectious diseases can be transmitted directly (contact, droplets) or indirectly (vehicles, vectors, air, fomites).

Susceptible Host

Infection/disease stages are: Incubation, onset/prodromal, advance/fastigium, defervescence, and convalescence.
Stages from infection to overt disease.

Active Immunity

Active immunity develops through infection or vaccination, leading to the production of antibodies and immune cells.

Passive Immunity

Passive immunity provides temporary protection through pre-formed antibody transfer.
This type of immunity, from maternal transfer or pre-made antisera, is temporary.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the fundamental concepts of health, disease, and causation through various historical perspectives. Understand the transition from early theories to germ theory and its implications in modern epidemiology. This quiz covers key definitions and frameworks essential for studying health sciences.