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EPIDEMIOLOGY definition and concept part -1.pptx
- 1. EPIDEMIOLOGY
- 2. • Introduction • History of definitions of epidemiology • Standard definition and Concept of epidemiology • Aims of epidemiology Contents
- 4. Epidemiology is all about asking questions…and getting answers that lead to further questions.
- 5. The science of the mass phenomena of infectious diseases or the natural history of infectious diseases. (Wade Hampton Frost 1927) DEFINITION OF EPIDEMIOLOGY HISTORY
- 6. DEFINITION OF EPIDEMIOLOGY HISTORY Epidemiology is, study of the distribution and determinants of diseases frequency in man. (MacMohan and Pugh,1960) The study of the disease, any disease, as a mass phenomenon. (Major Greenwood 1935)
- 10. Epidemiology is the study of the distribution and determinants of health related states or events or behaviour (including diseases) and application of this study to the control of diseases and other health problems. DEFINITION BY WHO
- 11. • The word ‘Epidemiology’ is based on the Greek words : • Epi = upon, or among; • Demos = people • Logos = study, knowledge
- 12. STANDARD DEFINITION OF EPIDEMIOLOGY “The study of the occurrence and distribution of health related events, states and processes in specific population, including the study of determinants influencing such processes and application of this knowledge to control relevant health problems.” (John.M.Last,1988)
- 14. Disease frequency Distribution of Disease Determinants of Disease The three important components of the definition of Epidemiology
- 15. Disease frequency Measures the occurrence of the disease Morbidity Mortality Incidence Number of deaths Prevalence
- 16. Basic tools to make measurements in epidemiology Disease frequency Rate Ratio Proportio n
- 17. Is Numerator a part of Denominator? Is time included in the denominator? Ratio (Sex ratio, MMR) Yes No Yes No Rate (Incidence) Proportion (Prevalence) Disease frequency
- 18. Disease distribution 3 parameters Time Place Person When ? Where ? Whom ?
- 20. • For diseases that occur seasonally Eg: Malaria Dengue Respiratory d/s - Eg: Influenza • Cyclical Eg; Measles- 2-3 yrs Influenza-5-6 yrs Rainy Winter
- 21. Seasonal Pattern of Rubella, Influenza and Rotavirus
- 23. Common source , single exposure epidemic
- 24. Common source , continuous exposure epidemic
- 26. Covid wave in India - Time distribution
- 27. Covid wave in Maharashtra-Time distribution
Editor's Notes
- You are asked to exercise regularly, you are asked to wear seat belt while driving, You are asked to get protected from mosquito bites. What are these? These are public health decisions. Who are responsible for this? Policy makers and health programmers . How they do this? . With help of epidemiology. shapes policy decisions and evidence – based practice by identifying risk factors for disease and targets for preventive health care.
- In 1927, W.H. Frost became the first professor of epidemiology in US. Later Major Greenwood became the first professor of epidemiology and medical statistics in the University of London
- Later Major Greenwood became the first professor of epidemiology and medical statistics in the University of London. In mid 1930s definition included any disease and also the prevalence of the disease and not just mere new cases. Mac mohan in 1960 gave almost the definition in use today, but they mentioned in man. Current def of epidemiology can also be applied to animals.
- The definitions of epidemiology available in online dictionaries and other media were easy to find but the quality of the definitions was heterogeneous. To determine the quality of definitions, quality criteria need to be used. For the definitions from 1978 to 2017, the quality criteria may seems subjective. Moreover, no weights were assigned to definitions. The choice of weighting criteria may be subjective. The purpose of the study was to identify concepts related to epidemiology and not to prioritize them. Given the variety of definitions, the fact that the method used to identify terms and concepts was easy to use and the fact that the majority of terms and concepts were present in more than 10% of definitions suggests that for the definitions retained all of the terms and concepts related to epidemiology were identified.
- Basic science of public health , both qualitative and quantitative
- Let us say if an under graduate medical student was asked to write an essay on common disease such as malaria.
- ow much is the disease? How frequently does it occur? For that we have to quantify the disease occurance
- Rate: N a part of D Ratio: N not a part of D Proportion: N a part of D
- That is, the epidemiologist examines whether there has been an increase or decrease of disease over time span; whether there is a higher concentration of disease in one geographic area than in others; whether the disease occurs more often in men or in a particular age-group, and whether most characteristics or behaviour of those affected are different from those not affected Epidemiology addresses itself to a study of these variations or patterns, which may suggest or lead to measures to control or prevent the disease. An important outcome of this study is formulation of aetiological hypothesis. This aspect of epidemiology is known as "descriptive epidemiology".
- Long term fluctuation/ secular trends. Based on the time trend, we can plan the preventive measures. Public health surveillance systems provide the data to monitor the frequency of health problems over time, and this is vitally important for identifying outbreaks and trends in disease frequency over time Epidemic: Occurrence of disease in particular area at a particular time
- For diseases that occur seasonally, health officials can anticipate their occurrence and implement control and prevention measures, such as an influenza vaccination campaign or mosquito spraying. For diseases that occur sporadically investigators can conduct studies to identify the causes and modes of spread, and then develop appropriately targeted actions to control or prevent further occurrence of the disease
- Figure 1.6 shows the seasonal patterns of rubella, influenza, and rotavirus. All three diseases display consistent seasonal distributions, but each disease peaks in different months — rubella in March to June, influenza in November to March, and rotavirus in February to April. The rubella graph is striking for the epidemic that occurred in 1963 (rubella vaccine was not available until 1969), but this epidemic nonetheless followed the seasonal pattern.
- For example, aseptic meningitis peaks at consistent yearly rates.
- In all situations, displaying the patterns of disease occurrence by time is critical for monitoring disease occurrence in the community and for assessing whether the public health interventions made a difference.