INTRO TO EPIDEMIOLOGY Flashcards
upon or leading the people
Study the occurrences and distribution of diseases
Distribution of determinants of health state or events in specified population and the application of this study to controls the health problems.
Epidemiology
Field of science given the relationship of various factors which determine the frequencies and distribution of an infectious process
Studies the patterns of disease occurrence in human populations and the factors that influence this pattern. The term obviously is related to epidemic
Epidemiology
Application of this study to the prevention or control of the disease or health problems
Epidemiology
Derived from the Greek words “epi” “demos” and “logos”
Epi: upon
Demos: people
Logos: study
Frequency vs Pattern:
Number of health events
Relative to population size
Frequency
Frequency vs Pattern:
Person (who)
Place (where)
Time (when)
Pattern
patterns of disease. pertains to the distribution of health-related states. This is under the descriptive statistics. We will study the frequency.
Epidemiology: Distribution
Ex: There are more deaths in males than on
females in an older age group.
The incidence of COVID-19 infection is
increasing in 15-24 age group in the
Philippines.
Cause of factors that bring about a change in health. Why? How? Biologic Chemical Other factors
Epidemiology: Determinants The focus is the risk factors. This falls under analytic. Example: People with family history of heart disease are more likely to developed heart disease than those without. Extreme sun exposure is a risk factor for skin cancer. Epidemiology
Dealing with population groups rather
than individuals as patients.
Epidemiology: Population
Clinical vs Epidemiological:
Signs and symptoms
Treatment
Clinical
Clinical vs Epidemiological:
Number of people affected
• Age groups affected
• Potential for spread
Epidemiological
Odd Man Out:
FUNCTIONS/SCOPE OF EPIDEMIOLOGY Describe health status Explain causal factors Predict occurrence of disease Approximate population distribution Control the spread of disease
Approximate population distribution
study of what the factors are, whether
risk factors or preventive factors.
Etiology
A if only the 1st statement is correct B if only the 2nd statement is correct C if both of the statements are correct D if neither of the statements is correct AIMS OF EPIDEMIOLOGY 1. To construct or complete the natural history of a disease so that adequate measures for diagnosis, treatment, and prevention will be made. 2. To study immediate and special problem in the field of health.
C
A if only the 1st statement is correct B if only the 2nd statement is correct C if both of the statements are correct D if neither of the statements is correct AIMS OF EPIDEMIOLOGY 1. To evaluate the effectiveness of therapy, preventive measures and program. 2. To give approximate about a parameter in a given population
A
EPIDEMIOLOGY: DEFINITION OF KEY TERMS: Frequency (including rates & risks) & pattern of health events (person, place, time).
Distribution
EPIDEMIOLOGY: DEFINITION OF KEY TERMS: factors or events that are capable of bringing about a change in health.
Determinants
EPIDEMIOLOGY: DEFINITION OF KEY TERMS: Epidemiology examines health events among population groups rather than individuals.
Human Population
EPIDEMIOLOGY: DEFINITION OF KEY TERMS: infections, chronic diseases & physiological events & various states of health such as disability, injury, mortality.
Health related states
EPIDEMIOLOGY: DEFINITION OF KEY
TERMS:
immunization, hospital attendance, bed occupancy.
Health related events
EPIDEMIOLOGY: DEFINITION OF KEY
TERMS:
basis for directing interventions.
Application
EPIDEMIOLOGY: DEFINITION OF KEY
TERMS:
an increase in the frequency (incidence) of a disease above the usual and expected rate, which is called endemic rate, thus epidemiology count cases of a disease, and when they detect the sign of epidemic, they ask who, when and where questions.
Epidemic
EPIDEMIOLOGY: DEFINITION OF KEY TERMS: surveillance made by the government before many people start dying
Notifiable disease
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
USES OF EPIDEMIOLOGY
1. Study the history of the health population and the rise and fall of diseases and changes in their
character.
2. Diagnose the health of individual patient only.
A
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
USES OF EPIDEMIOLOGY
1. Study the work of health services without even a view of improving them.
2. Estimate the risk of diseases, accidents, detects and the changes avoiding them
B
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
USES OF EPIDEMIOLOGY
1. Complete the clinical feature of acute disease and not describe their natural history.
2. Not focused in the search for cause of health and
disease.
D
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
Early explanations for disease: Ancient Greeks
- Wrath of Gods
- Evil Sprits
C
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
Early explanations for disease: Ancient Greeks
1. Religious Beliefs
2. Weather
C
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
Early explanations for disease: Ancient Greeks
1. “Bad Air” Theory (Miasmic theory)
2. The Great Cataclysm
A
Theory that says that Miasma (Bad Air) causes the disease, particularly fever. Thus, they build huge fires to purify the air.
“Bad Air” Theory (Miasmic theory)
He is considered as the
“Father of Medicine”, theorized the “Filth Theory”
Hippocrates (400 BC)
this theory associates the disease with physical environment. Changes in seasons, climate, temperature and overcrowding causes diseases. Diseases were due to poisonous substances and gases from the Earth.
“Filth Theory” Physical Environment as Factors influencing Disease. 1. Changing seasons 2. Hot and Cold Winds 3. Qualities of Water
Has written books and bills (Bills of Mortality in 1669). This bill contains his natural and political observations. He is the first one to perform descriptive statistics like the tabulated births and deaths, occurrences of census and patterns in mortality (organizing mortality data in a mortality table) which is referred as the Columbus of
statistics
John Graunt (1669)
During his time, they know that murder is
the number one cause of death. Later on,
he found out that it was infant mortality
created a warning system on
the Bubonic Plague (Yersinia pestis).
John Graunt (1669) Quantitative methods in describing vital population statistics. 1. Seasonal Variations 2. Infant Mortality 3. Excess male over female differences in mortality. 4. First to discover regularities in mortality
Considered as the
“Father of Handwashing”.
Pioneer of antiseptic procedures
He found out that medical students did not disinfect and follow antiseptic procedure every after patient
Ignaz Semmelweis (1840) Investigated why mortality rate from childbed fever was higher in the clinic for medical students than that for midwives
He is considered as the “Father of Modern Epidemiology”. Utilized methods that reflects modern field of epidemiology. Investigated the source of Cholera outbreak
John Snow (1849-1854) He performed the shoe leather epidemiology. He has direct door to door inquiry of the affected populations. He noted that districts with high cholera rates were serviced by two companies, which is the Lambeth and the Southwark and Vauxhall company
refuted the Miasmic theory (Bad
Air) for Cholera. Before, they know that
cholera was due to bad air
John Snow (1849-1854) Natural Experiment - naturally occurring circumstances in which groups of people have different levels of exposure to a factor causal in a way that is similar to an actual experiment
“Germ / Bacteriological Theory” Diseases caused by specific living organisms: Due to microscopic forms of life. Opened the concepts of isolation and quarantine.
Robert Koch (1884)
Postulates:
-Microorganisms must be observed in all cases.
-It must be isolated and grown in pure cultures.
-The pure cultures when inoculated in a susceptible animal, must reproduce the disease.
-The microorganisms must be observed in and recovered from the experimented diseased animals.
What year or era?
Explosion of investigation of disease occurrences.
Development of epidemiologic methods for non- communicable diseases.
1990s
It is a longitudinal study that started in 1949. They recruited diseased-free men and women. The initial medical history and physical examinations were taken and it was held for every 2 years
Framingham Study
The risk factors for CHD (congenital heart defect) and CVD (cardiovascular diseases).
This is for the smoking to lung cancer. This was during 1951- 2000. They enrolled thousands of male doctors and provided strong evidence linking smoking to lung cancer
British Doctors Study (Doll and Peto Study)
theory about disease results from the interaction of multiple ecological factors within a dynamic system. It is made up of the agent of the disease, host and the environment
Theories on Multiple Causation
MODELS OF DISEASE CAUSATION: States that effects never depend on single isolated causes but rather develop as the result of chains of causation → result of complex genealogy and antecedents.
THE WEB
MODELS OF DISEASE CAUSATION:
The host and agent are at the opposite ends of a hypothetical lever while the environment serves as fulcrum.
Based on biologic laws:
Disease results from an imbalance between disease agent and man
EPIDEMIOLOGIC LEVER
The nature and extent of the imbalance depends on the nature and characteristics of the host and the agent. The characteristic of the two are influenced considerably by the conditions of their environment.
A if only the 1st statement is correct
B if only the 2nd statement is correct
C if both of the statements are correct
D if neither of the statements is correct
TWO MAIN AREAS OF INVESTIGATION
1. Describes the distribution of health status in terms of age, gender, race, geography, and time
2. Patterns of disease distribution in terms of causal factor
C
In epidemiology of any disease or event, one studies the factor which contribute to its causation and behavior- AGENT, HOST, ENVIRONMENT
Epidemiology concept maintains that there can be no single cause of disease.
is any element, substance or force whether living or non- living thing; the presence or absence can initiate or perpetuate a disease process.
Agent
Types of Agents: Living
BVFPH (Biological organisms capable of causing
diseases)
Bacteria: Mycobacterium tuberculosis, Shigellosis • Viruses: AIDS, Hepatitis • Fungi: Candidiasis, Athletes Foots, Mycosis • Protozoans: Amoebiasis, Jorjasis • Helminths: Schistosomiasis, Ascariasis
Types of Agents: Non-living
PCN
• Physical and Mechanical: Extremes of temperature, light, electricity, physical trauma.
• Chemicals: could be exogenous (poisons) or endogenous (accumulation of toxic products of metabolism).
• Nutrients: Deficiency agents (Anemia
from iron deficiency) and Excess agents
(Obesity from over eating)
CHARACTERISTICS OF AGENT OF DISEASE: The physical features, the biological requirement, chemical composition, and the resistance
Inherent characteristics
CHARACTERISTICS OF AGENT OF DISEASE: It refers to the reservoir and the source of infection and the modes of transmission
Characteristic in relation to the
environment
CHARACTERISTICS OF AGENT OF DISEASE: ability to gain access and adapt to the human host to the extent of finding lodgment and multiplication
Characteristic directly related to man
(Infectivity)
CHARACTERISTICS OF AGENT OF DISEASE: measures the ability of the agent, when lodged in the body set up a specific reaction.
Characteristic directly related to man
Pathogenicity
CHARACTERISTICS OF AGENT OF DISEASE: refers to severity of the reaction produce and is usually measured in terms of fatality
Characteristic directly related to man
Virulence
CHARACTERISTICS OF AGENT OF
DISEASE
ability to stimulate the
host to produce antibody.
Antigenicity
Mechanisms by which an infectious
agent is transported from reservoir to
susceptible human host
MODES OF TRANSMISSION
MODES OF TRANSMISSION:
immediate transfer of infectious agent on a receptive portal of entry.
Direct transmission
MODES OF TRANSMISSION:
any substance that serves as an intermediate means to transport and introducing infectious agent into susceptible host through a suitable portal of entry. i.e. Fomites (inanimate objects or materials) such as handkerchiefs, toys, soiled clothes, cooking or eating utensils, and surgical instruments or dressing can act as a vehicle.
Indirect transmission
Vehicle borne
MODES OF TRANSMISSION:
Transmission may occur by injecting salivary gland fluid during biting or by depositing feces or other materials on the skin through the bite wound or a traumatized skin area
Indirect transmission
Vector-borne
MODES OF TRANSMISSION:
transmission is facilitated by a mechanical vector, an animal that carries a pathogen from one host to another without being infected itself. For example, a fly may land on fecal matter and later transmit bacteria from the feces to food that it lands on; a human eating the food may then become infected by the bacteria, resulting in a case of diarrhea or dysentery
Indirect transmission (Mechanical vector)
MODES OF TRANSMISSION:
occurs when the pathogen reproduces within a biological vector that transmits the pathogen from one host to another. Arthropods are the main
vectors responsible for biological transmission. Most arthropod vectors transmit the pathogen by biting the host, creating a wound that serves as a portal of entry
Indirect transmission
Biological vector
MODES OF TRANSMISSION:
dissemination of microbial aerosols to a suitable portal of entry usually the respiratory tract
Airborne a. Droplet- usually small residues which result from evaporation of fluid from droplets emitted by an infected host. b. Dust
It goes through chain of events leading from inapparent infection to a clinical case of a disease. We will check the gradient of the infection, the range from inapparent to severe disease
The HOST Factor of Disease
- Age
- Sex
- Race
- Habits, Customs and Religions
- Exposure to agent
- Defense mechanism of the host
The HOST Factor of Disease:
- immune system; deals with antigens from pathogens
that are freely circulating or outside the infected sites
Humoral defense
The HOST Factor of Disease:
occurs inside the infected cells and is mediated by T lymphocytes. Antigens are expressed on the cells surface or on an antigen presenting cell
(APC).
Cellular defense
This is the total property of an individual
to protect himself from an infectious
agent
IMMUNITY
Two types of immunity:
______- present at the time of birth or has developed
during maturation.
______- acquired as a result of prior exposure with a
foreign substance.
Non-specific resistance
Specific resistance
First line of defense: Skin mucosal surface Tears Saliva acid pH of gastric juice phagocytes & macrophages Age, nutrition status, genetic factors
NON-SPECIFIC DEFENSE
MECHANISMS
SPECIFIC RESISTANCE:
what has been introduced to the individual is the antigen (weakened type). Naturally acquired active immunity infective agent will gain entry to the body, it acts as a stimulant for the antibody formation as the organism acts as the antigen.
Artificially acquired active immunity when the antigen has been deliberately
introduced like injecting vaccines.
Active Immunity
Live vaccine: a vaccine in which a live virus is weakened or attenuated through chemical and physical properties. It is done for the vaccine to produce an immune response without causing the severe effects of the disease
SPECIFIC RESISTANCE:
when what has been introduced
is already your antibody
a. Naturally acquired passive immunity-exhibited by the transfer of antibodies from mother’s placenta to the fetus and transfer of antibodies from breast milk to the baby.
e. g. First drop of milk: Colostrum
b. Artificially acquired passive immunity- injection of artificially prepared substance like immune serum of your gamma globulin.
Immunity of a group or a community.
“Resistance” of a group to invasion and spread of an infectious agent based on the immunity of a high proportion of individuals member of the group. Important factor underlying the dynamics of propagated epidemics
HERD IMMUNITY
COMMUNITY REACTIONS TO AGENT:
Intermittent presence of a disease.
Occurrence of a few cases every now and then often without relationship to each other
SPORADIC
COMMUNITY REACTIONS TO AGENT:
Constant presence of a disease within a geographical area. (Malaria endemic in Palawan, Schistosomiasis which is endemic in region 8)
ENDEMIC
COMMUNITY REACTIONS TO AGENT:
Occurrence in a community of cases of
an illness clearly in excess of normal
expectancy
EPIDEMIC (OUTBREAK)
COMMUNITY REACTIONS TO AGENT: An outbreak of exceptional proportion spreading quickly from one area to another. Epidemic of worldwide proportion
PANDEMIC
It enhances or it diminishes survival of the agents. The environment can serve to bring the agent and the host into contact. Also, the environment is a reservoir that
foster the infectious disease agent.
The ENVIRONMENTAL Factors of
Disease
Physical Environment
Climate (certain disease have seasonal distribution, e.g., dengue during rainy season)
Geography and location
Biologic Environment (Living environment of a man consisting of plants, animals and fellow human beings)
Socio-economic environment
Living organism or inanimate matter in which an infectious agent normally lives and multiplies on which
the agent depends primarily for survival and reproduces itself in such manner that it can be transmitted to a susceptible host
RESERVOIR Reservoir of infection - Physical environment - Animals or insects - Human beings (main reservoirs)
______- each slice of the pie is a factor contributing to the development of the disease. It could be any host agent or environmental factors.
______- a component cause that is present in every sufficient cause. This is required. Factor must be present for the disease to occur. It must invariably precede an effect.
______- set of conditions that inevitably results to the outcome. It includes component causes. That is the completion pie. This completion will result to disease development.
Component cause
Necessary cause
Sufficient cause
TYPES OF CAUSAL RELATIONSHIPS:
Without the factor, disease never develops. With the factor, disease always develops. This situation rarely occurs.
Necessary and sufficient
TYPES OF CAUSAL RELATIONSHIPS:
The factor in and of itself is not enough to cause disease. Multiple factors are required, usually in a specific temporal sequence, such as the carcinogenesis
Necessary but not sufficient
TYPES OF CAUSAL RELATIONSHIPS:
The factor alone can cause disease but so
can other factors in its absence. An example of this is the benzene or radiation, it can cause leukemia
without the presence of the other
Sufficient but not necessary
TYPES OF CAUSAL RELATIONSHIPS:
The factor cannot cause disease on its own nor is it the only factor that can cause the disease. This is the Probable Model of Chronic Disease Relationships
Neither sufficient nor necessary
Progression of a disease process in an individual over time, on the absence of treatment (CDC)
NATURAL HISTORY OF THE DISEASE
2 Phases of NATURAL HISTORY OF THE DISEASE:
Phase before man is involved. Through interaction of the agent, host, and environmental factors, agent
finally reaches man. Under this is the Susceptibility and Adaptation
PRE-PATHOGENESIS
2 Phases of NATURAL HISTORY OF THE DISEASE:
includes the success invasion and establishment of the agent in the host. From incubation period to production of detectable evidence of the disease
process (Clinical Horizon), until it is interrupted by treatment. Under this is the Sub-Clinical, Clinical
Stage, and the Outcome
PATHOGENESIS
Pre-exposure period in the natural history of disease (pre-pathogenesis), in which the individual in the population is vulnerable or at risk to acquire the infection and/or amenable to get exposed to and be harmed by a health determinant.
SUSCEPTIBILITY STAGE During this stage, the individual in the population does not have the disease nor the infection. It is the risk factors that are present. The susceptibility stage ends with the effective exposure.
The etiological factors (e.g. infectious agent, risk behaviors, environmental toxins) are present in the body and are causing pathological changes, but
there are not yet any discernible signs or symptoms
STAGE OF PRESYMPTOMATIC DISEASE (SUBCLINICAL STAGE) There is no manifest of disease but pathogenic changes have started to occur. The time required for the agent to establish itself, multiply and produce toxins. Incubation and Latency: Asymptomatic
Refers to the period of time at the onset of signs or symptoms of the disease. Sufficient end-organ changes have occurred so that there are recognizable signs or symptoms of disease
STAGE OF CLINICAL DISEASE
Morphologic subdivision or on functional or therapeutic
considerations
Before the risk factors.
Prevent development of risk factors.
Target: The general population, mostly the young ones
PRIMORDIAL PREVENTION
The phase of disease of this one is the underlying social and environmental conditions leading to causation. The aim of this level is to establish and maintain conditions that minimize hazards to health
Pre-pathogenesis Prevent disease: - Reduction of risk factors - Immunization - Removal of harmful agents
PRIMARY PREVENTION
Target: Susceptible groups in the population.
The phase of disease of this is the specific causal factors.
The aim of this is to reduce the incidence of disease
Subclinical Early detection Prompt treatment Cure disease at the earliest stage Target: Patients that are at the earliest stage of disease
SECONDARY PREVENTION
The phase of disease of this is the earliest stage of disease. The aim of this is to reduce the prevalence of the disease by shortening its duration
Complete treatment Limit disability Rehabilitation Target: People with disease at the late stage
TERTIARY PREVENTION
The phase of disease of this is the late stage of disease (treatment and rehabilitation stage)
The aim of this is to reduce the number or impact on the complication
Method of grouping of diseases based on their specific features.
Ensures universal criteria for
diagnosing diseases
CLASSIFICATION OF DISEASES
Usually dependent on current level of knowledge about the disease
Diagnostic classification standard for all clinical and research purposes
Used by more than 100 countries worldwide
INTERNATIONAL CLASSIFICATION OF
DISEASES (ICD)
Assign codes for diseases, disorders, injuries, and other related health conditions.
