Epidemiology
- 2. CONTENTS INTRODUCTION HISTORY AIMS OF EPIDEMIOLOGY EPIDEMIOLOGIC TRIAD CHAIN OF INFECTION TASKS OF AN EPIDEMIOLOGIST CONCLUSION
- 3. INTRODUCTION • Epidemiology is the cornerstone of public health, and shapes policy decisions and evidence – based practice by identifying risk factors for disease and targets for preventive health care.
- 4. DEFINITIONS • Epidemiology is the branch of medical science which deals with the treatment of epidemics. (Thomas Parkin,1873) • The study of the distribution and determinants of disease frequency in man. (MacMahon,1960)
- 5. THE MOST WIDELY ACCEPTED THEORY • Epidemiology is the study of the distribution and determinants of health-related states or events, in specified populations and the application of this study to the control of diseases and other health problems. • (John.M.Last ,1998)
- 6. ETYMOLOGY • The word ‘Epidemiology’ is based on the Greek words : • Epi = upon, or befall; • Demos = people • Logos = study, knowledge
- 8. HISTORY TIMELINE CIRCA 400 B.C. first person known to have examined the relationships between the occurrence of disease and environmental influences. Snow conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence. Epidemiologists focused their methods on acute infectious and non- infectious diseases. There has been an explosion in the development of research methods and the theoretical underpinnings of epidemiology. 1854 1930 - 1940 WORLD WAR
- 9. HISTORY TIMELINE Health workers applied epidemiologic methods to eradicate naturally occurring smallpox 1970 – 1980 1990 The related fields of molecular and genetic epidemiology took root
- 10. 1854 • John Snow, famous for his investigations into the causes of the 19th century cholera epidemics. • He is known as the ‘Father of Modern Epidemiology’. • Snow conducted studies of cholera outbreaks both to discover the cause of disease and to prevent its recurrence. • This has been perceived as a major event in the history of public health and regarded as the founding event of the science of epidemiology having shaped public health policies around the world.
- 11. AIMS OF EPIDEMIOLOGY • According to the International Epidemiological Association (IEA), Epidemiology has three main aims : • To describe and analyse disease occurrences and the distribution in human populations. (Descriptive Epidemiology) • To identify the etiologic factors in the pathogenesis of disease. (Analytical Epidemiology) • To provide the data essential in planning, implementation and evaluation of services for the prevention, control and treatment of disease and setting up priorities among those services. (Experimental Epidemiology)
- 13. DEFINITION • The triad consists of external agent, a susceptible host, and an environment that brings the host and agent together. • In this model, disease results from the interaction between the agent and the susceptible host in an environment that supports transmission of the agent from a source to that host.
- 14. AGENT • The first link in the chain of disease transmission is a disease agent. • The disease may have a single agent, but more factors are responsible for disease transmission.
- 16. OTHER AGENTS: • Mechanical Agents • Nutritional Agents • Social Agents • Hormonal and Chromosomal factors
- 17. HOST • It refers to the human who is susceptible to the disease. • A variety of factors intrinsic to the host, sometimes called risk factors can influence an individual’s exposure, susceptibility or response to a causative agent. • Susceptibility and response to an agent are influenced by factors such as age, gender, hereditary, nutrition, occupation, custom habits, immunity, marital status, socio-economic status and life-style factors.
- 18. ENVIRONMENT • It refers to extrinsic factors that affect the agent and the opportunity for exposure. • Environmental factors such as geology, and climate, biologic factors such as insects that transmit the agent, and socio-economic factors such as crowding, sanitation, and the availability of health services.
- 19. TYPHOID FEVER Polluted water. Open defecation. Salmonella Typhi Young age, more in the males, low immunity power, lack of personal hygiene
- 20. CHAIN OF INFECTION • The traditional epidemiologic triad model holds that infectious diseases results from the interaction of agent, host and environment. • Transmission occurs when the agent leaves its reservoir or host through a portal of exit, is conveyed by some mode of transmission and enters through an appropriate portal of entry to infect a susceptible host. This sequence is sometimes called the chain of infection.
- 22. PORTAL OF EXIT : The path by which an pathogen leaves the host. MODE OF TRANSMISSION : An infectious agent may be transmitted from its natural reservoir to a susceptible host in different ways. PORTAL OF ENTRY : The portal of entry refers to the manner in which a pathogen enters a susceptible host. SUSCEPTIBLE HOST : It depends on the genetic, constitutional factors, specific immunity, and non-specific factors that affect an individual’s ability to resist infection or to limit the pathogenicity. RESERVOIR : The habitat in which the agent normally lives, grows and multiplies.
- 23. DISEASE PREVENTION AND CONTROL • Knowledge of the portals of exit and entry and modes of transmission provides a basis for determining appropriate control measures. • Early diagnosis • Epidemiological Investigation • Isolation • Treatment • Quarantine
- 24. TASKS OF AN EPIDEMIOLOGIST • Surveillance • Investigation • Analysis and Interpretation • Communication • Evaluation • Research • Management
- 25. CONCLUSION • As the basic science of public health, epidemiology includes the study of frequency, patterns, and causes of health-related states or events in populations, and the application of that study to address public health issues. • Epidemiologists use a systematic approach to assess the What, Who, Where, When, and Why/How of these health states or events. • Core epidemiologic tasks of a public health epidemiologist include public health surveillance, field investigation, research, evaluation, and policy development. In carrying out these tasks, the epidemiologist is almost always part of the team dedicated to protecting and promoting the public's health.
- 26. REFERENCES • SOBEN PETER - ESSENTIALS OF PUBLIC HEALTH DENTISTRY (5th Edition) • https://en.wikipedia.org/wiki/Epidemiology • http://www.who.int/topics/epidemiology/en/