Epidemiology Fundamentals

Epidemiology

• Study of the distribution and determinants of health-related states or events in specified populations, and application of this study to control of health problems.
• Focuses on frequency and pattern of health events in a population, including time, place, and person.

Distribution

• Refers to the frequency and pattern of health events in a population.
• Frequency includes the number of health events and its relationship to the size of the population.
• Pattern refers to the occurrence of health-related events by time, place, and person.
• Time patterns may be annual, seasonal, weekly, daily, hourly, or any other breakdown of time that influences disease or injury occurrence.
• Place patterns include geographic variation, urban/rural differences, and location of work sites or schools.
• Personal characteristics (person) include demographic factors, behaviors, and environmental exposures that may be related to risk of illness, injury, or disability.

Determinants

• Refers to the causes and other factors (risk factors) that influence the occurrence of disease and other health-related events.
• Any factor, event, characteristic, or other definable entity that brings about a change in a health condition or other defined characteristic.

Health-related States or Events

• Anything that affects the well-being of a population, including disease, illness, injury, or disability.

Application

• Applying the knowledge gained by the studies to community-based practice to control health problems.

History of Epidemiology

• Hippocrates (400BC): attempted to explain disease occurrence from a rational rather than a supernatural viewpoint.
• John Graunt (1662): first to employ quantitative methods in describing population vital statistics.
• Edward Jenner (1796): discovered that it is possible to vaccinate against Small Pox using material from Cow Pox.
• John Snow: investigated a cholera epidemic in mid-19th century London and is considered the "Father of field epidemiology".
• Koch (late 1800s): discovered that some diseases are caused by living organisms.
• Framing Heart Study (1949): identified risk factors for coronary heart disease.
• Salk (1954): developed the Polio Vaccine.
• Doll and Peto (Post WWII): associated smoking with Lung Cancer.
• Eradication of smallpox (1980).

Uses of Epidemiologic Studies

• To identify the etiology or cause of the disease.
• To determine the natural history and prognosis of the disease.
• To identify risk factors and high-risk groups.
• To determine the extent of disease found in the community.
• To identify health programs, adequate measures for diagnosis, treatment, and prevention of diseases.
• To evaluate the effectiveness of existing health programs, therapy, and preventive measures.

Types of Epidemiology

• Classical: population-oriented, studies the community origins of health problems, and focuses on discovering risk factors that might be altered in a population to prevent or delay disease, injury, and death.
• Clinical: studies patients in health care settings, goal is to improve the prevention, early detection, diagnosis, treatment, prognosis, and care of illness in individual patients.
• Infectious Disease: a disease caused by a microorganism, potentially infinitely transferable to new individuals, may or may not be communicable.

Communicable and Contagious Disease

• Communicable Disease: an infectious disease that is contagious and can be transmitted from one source to another by infectious bacteria or viral organisms.
• Contagious Disease: a very communicable disease capable of spreading rapidly from one person to another.

Pre-pathogenic and Pathogenic Phases

• Pre-pathogenic Phase: phase before man is involved, preliminary interaction of potential agent, host, and environmental factors in disease production, everyone is in the period of pre-pathogenesis.
• Pathogenic Phase: course of disorder in man from the first interaction with the disease, provoking stimuli to the changes in form and function which result or until equilibrium is reached or recovery, defect, disability, or death ensues.

Requirements for Successful Agent Invasion

• Conditions in the environment must be favorable to the agent.
• Susceptible host.
• Satisfactory portal of entry.
• Accessibility of portal of exit from the host.
• Appropriate means of dissemination and transmission to a new host.

Epidemiology

• Study of the distribution and determinants of health-related states or events in specified populations, and application of this study to control of health problems.
• Focuses on frequency and pattern of health events in a population, including time, place, and person.

Distribution

• Refers to the frequency and pattern of health events in a population.
• Frequency includes the number of health events and its relationship to the size of the population.
• Pattern refers to the occurrence of health-related events by time, place, and person.
• Time patterns may be annual, seasonal, weekly, daily, hourly, or any other breakdown of time that influences disease or injury occurrence.
• Place patterns include geographic variation, urban/rural differences, and location of work sites or schools.
• Personal characteristics (person) include demographic factors, behaviors, and environmental exposures that may be related to risk of illness, injury, or disability.

Determinants

• Refers to the causes and other factors (risk factors) that influence the occurrence of disease and other health-related events.
• Any factor, event, characteristic, or other definable entity that brings about a change in a health condition or other defined characteristic.

Health-related States or Events

• Anything that affects the well-being of a population, including disease, illness, injury, or disability.

Application

• Applying the knowledge gained by the studies to community-based practice to control health problems.

History of Epidemiology

• Hippocrates (400BC): attempted to explain disease occurrence from a rational rather than a supernatural viewpoint.
• John Graunt (1662): first to employ quantitative methods in describing population vital statistics.
• Edward Jenner (1796): discovered that it is possible to vaccinate against Small Pox using material from Cow Pox.
• John Snow: investigated a cholera epidemic in mid-19th century London and is considered the "Father of field epidemiology".
• Koch (late 1800s): discovered that some diseases are caused by living organisms.
• Framing Heart Study (1949): identified risk factors for coronary heart disease.
• Salk (1954): developed the Polio Vaccine.
• Doll and Peto (Post WWII): associated smoking with Lung Cancer.
• Eradication of smallpox (1980).

Uses of Epidemiologic Studies

• To identify the etiology or cause of the disease.
• To determine the natural history and prognosis of the disease.
• To identify risk factors and high-risk groups.
• To determine the extent of disease found in the community.
• To identify health programs, adequate measures for diagnosis, treatment, and prevention of diseases.
• To evaluate the effectiveness of existing health programs, therapy, and preventive measures.

Types of Epidemiology

• Classical: population-oriented, studies the community origins of health problems, and focuses on discovering risk factors that might be altered in a population to prevent or delay disease, injury, and death.
• Clinical: studies patients in health care settings, goal is to improve the prevention, early detection, diagnosis, treatment, prognosis, and care of illness in individual patients.
• Infectious Disease: a disease caused by a microorganism, potentially infinitely transferable to new individuals, may or may not be communicable.

Communicable and Contagious Disease

• Communicable Disease: an infectious disease that is contagious and can be transmitted from one source to another by infectious bacteria or viral organisms.
• Contagious Disease: a very communicable disease capable of spreading rapidly from one person to another.

Pre-pathogenic and Pathogenic Phases

• Pre-pathogenic Phase: phase before man is involved, preliminary interaction of potential agent, host, and environmental factors in disease production, everyone is in the period of pre-pathogenesis.
• Pathogenic Phase: course of disorder in man from the first interaction with the disease, provoking stimuli to the changes in form and function which result or until equilibrium is reached or recovery, defect, disability, or death ensues.

Requirements for Successful Agent Invasion

• Conditions in the environment must be favorable to the agent.
• Susceptible host.
• Satisfactory portal of entry.
• Accessibility of portal of exit from the host.
• Appropriate means of dissemination and transmission to a new host.

Epidemiology

• Study of the distribution and determinants of health-related states or events in specified populations, and application of this study to control of health problems.
• Focuses on frequency and pattern of health events in a population, including time, place, and person.

Distribution

• Refers to the frequency and pattern of health events in a population.
• Frequency includes the number of health events and its relationship to the size of the population.
• Pattern refers to the occurrence of health-related events by time, place, and person.
• Time patterns may be annual, seasonal, weekly, daily, hourly, or any other breakdown of time that influences disease or injury occurrence.
• Place patterns include geographic variation, urban/rural differences, and location of work sites or schools.
• Personal characteristics (person) include demographic factors, behaviors, and environmental exposures that may be related to risk of illness, injury, or disability.

Determinants

• Refers to the causes and other factors (risk factors) that influence the occurrence of disease and other health-related events.
• Any factor, event, characteristic, or other definable entity that brings about a change in a health condition or other defined characteristic.

Health-related States or Events

• Anything that affects the well-being of a population, including disease, illness, injury, or disability.

Application

• Applying the knowledge gained by the studies to community-based practice to control health problems.

History of Epidemiology

• Hippocrates (400BC): attempted to explain disease occurrence from a rational rather than a supernatural viewpoint.
• John Graunt (1662): first to employ quantitative methods in describing population vital statistics.
• Edward Jenner (1796): discovered that it is possible to vaccinate against Small Pox using material from Cow Pox.
• John Snow: investigated a cholera epidemic in mid-19th century London and is considered the "Father of field epidemiology".
• Koch (late 1800s): discovered that some diseases are caused by living organisms.
• Framing Heart Study (1949): identified risk factors for coronary heart disease.
• Salk (1954): developed the Polio Vaccine.
• Doll and Peto (Post WWII): associated smoking with Lung Cancer.
• Eradication of smallpox (1980).

Uses of Epidemiologic Studies

• To identify the etiology or cause of the disease.
• To determine the natural history and prognosis of the disease.
• To identify risk factors and high-risk groups.
• To determine the extent of disease found in the community.
• To identify health programs, adequate measures for diagnosis, treatment, and prevention of diseases.
• To evaluate the effectiveness of existing health programs, therapy, and preventive measures.

Types of Epidemiology

• Classical: population-oriented, studies the community origins of health problems, and focuses on discovering risk factors that might be altered in a population to prevent or delay disease, injury, and death.
• Clinical: studies patients in health care settings, goal is to improve the prevention, early detection, diagnosis, treatment, prognosis, and care of illness in individual patients.
• Infectious Disease: a disease caused by a microorganism, potentially infinitely transferable to new individuals, may or may not be communicable.

Communicable and Contagious Disease

• Communicable Disease: an infectious disease that is contagious and can be transmitted from one source to another by infectious bacteria or viral organisms.
• Contagious Disease: a very communicable disease capable of spreading rapidly from one person to another.

Pre-pathogenic and Pathogenic Phases

• Pre-pathogenic Phase: phase before man is involved, preliminary interaction of potential agent, host, and environmental factors in disease production, everyone is in the period of pre-pathogenesis.
• Pathogenic Phase: course of disorder in man from the first interaction with the disease, provoking stimuli to the changes in form and function which result or until equilibrium is reached or recovery, defect, disability, or death ensues.

Requirements for Successful Agent Invasion

• Conditions in the environment must be favorable to the agent.
• Susceptible host.
• Satisfactory portal of entry.
• Accessibility of portal of exit from the host.
• Appropriate means of dissemination and transmission to a new host.