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UNIT III NATURAL HISTORY OF DISEASE PDF.pdf
The document discusses the natural history of disease and the epidemiological triad. It defines the natural history of disease as the progression of a disease from exposure to an agent until resolution via recovery or death without intervention. There are typically stages of susceptibility, subclinical disease, clinical disease, and finally recovery, disability, or death. The epidemiological triad model describes the interaction between an external agent, host, and environment that results in disease. When these factors are not in balance, epidemics can arise. The document also notes that epidemiology examines disease patterns and causation at the community level.
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UNIT III NATURAL HISTORY OF DISEASE PDF.pdf
- 1. Natural History ofDisease
- 2. Burhan Uddin, Karachi 2 Objectives At thecompletion of this unit, the learners will be able to: 1. Define the host, agent and environment terms. 2. Identify the concept of epidemiology and diseases with the help of Epidemiological Triad. 3. Identify Epidemiological approach in community setting.
- 3. Natural History ofDisease Iceberg Theory of Disease 3 Burhan Uddin, Karachi
- 4. 4 Iceberg Model /Theory • The iceberg model is a systems thinking tool designed to help an individual or group discover the – patterns of behavior, – supporting structures, and – mental models that underlie a particular event. Burhan Uddin, Karachi
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- 6. 6 Natural History ofDisease • The natural history of disease is the course a disease takes in individual people from its pathological onset ("inception") until its eventual resolution through complete recovery or death. • Natural history of disease refers to the progress of a disease process in an individual over time, in the absence of intervention. • This is the continuous progression in an individual of the disease from the moment of exposure to the causal agents. Burhan Uddin, Karachi
- 7. 7 Natural History ofDisease • Reflect on the four major possible outcomes in an individual of exposure to a causal agent. – First, the exposure may have no visible effect. – Second, there may be demonstrable damaging effect of the exposure which may be repaired. – Third, the effect may be an illness that is rapidly contained by the body's defence mechanism. – Finally, the illness may progress until it leads to continuing long term problems, irreversible damage or death. Burhan Uddin, Karachi
- 8. 8 Natural History ofDisease • The process begins with exposure. • Without medical intervention, the process ends with – recovery, – disability, or – death Burhan Uddin, Karachi
- 9. 9 Stages in NaturalHistory of Disease • The stages in the natural history of disease are: – stage of susceptibility – stage of subclinical disease – stage of clinical disease – stage of recovery, disability or death Burhan Uddin, Karachi
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- 12. 12 Stages of NaturalHistory Disease Stage of Susceptibility – Begins with appropriate exposure to accumulation of factors sufficient for the disease process to begin in susceptible host. Stage of Sub clinical disease – not clinically apparent and disease will not develop; pathological changes occur but individual unaware, diagnosed by antibody response or culture. Best time for screening. Stage of clinical disease – clinically apparent, this is the best time for diagnosis. Stage of Recovery, Disability or Death – Ultimately, the disease process ends either in recovery, disability or death. Burhan Uddin, Karachi
- 13. Figure: Time Infancy childhood adolescenceadulthood old age Full health Death 13 Burhan Uddin, Karachi
- 14. Figure: Causes begin toexert their influence here Disease and first manifestationcan be diagnosed here, e.g.. MI Time Infancy childhood adolescence adulthood old age Full health Death Recurrence and death 14 Burhan Uddin, Karachi
- 15. Class Group Activity •Take name of common disease in Pakistan • Relate that disease into stages of Natural History Disease • Then share with whole class 15 Burhan Uddin, Karachi
- 16. 16 Applications of NaturalHistory ⚫Natural history is vital for disease prevention policies. ⚫It underlies secondary prevention based on screening ⚫It provides a rationale for all health care. ⚫Purpose of health care, including medicine, is to influence the natural history of disease by reducing and delaying ill-health. ⚫When achieved through purposeful actions by societies the collective endeavour is public health. Burhan Uddin, Karachi
- 17. past Present future Public health andmedical action Time Infancy childhood adolescence adulthood old age Full health Death 17 Burhan Uddin, Karachi
- 18. 18 Population Pattern ofDisease (PPOD confused with the changing pattern of disease ⚫ Natural history of disease should not be (but is) in populations. ⚫ The distribution of a disease across socio-economic groups may change as it has for coronary heart disease. ⚫ This is called as “Population pattern of disease” ⚫ Main measures of PPOD are the disease incidence and prevalence. Burhan Uddin, Karachi
- 19. 19 Disease Process The aspectsof disease process include ⚫Etiology ⚫ Pathogenesis ⚫ Morphologic changes ⚫ Clinical manifestations ⚫ Diagnosis ⚫Clinical course Burhan Uddin, Karachi
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- 22. Web of Causation 22 BurhanUddin, Karachi
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- 24. Epidemiologic Triangle ⚫A traditionalmodel of infectious disease causation, known as the Epidemiologic Triad ⚫The triad consists of an external agent, a host and an environment in which host and agent are brought together, causing the disease to occur in the host. ⚫Epidemiologic Homeostasis Host Agent Environment Host Environment Agent 25 Burhan Uddin, Karachi
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- 27. Epidemiologic Triangle 27 BurhanUddin, Karachi
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- 36. 36 Concept of Epidemiology& Disease vs Epidemiological Triad Epidemics arise when host, agent, and environmental factors are not in balance Due to new agent Due to change in existing agent (infectivity, pathogenicity, virulence) Due to change in number of susceptibilities in the population Due to environmental changes that affect transmission of the agent or growth of the agent Burhan Uddin, Karachi
- 37. Epidemiology Approach in CommunitySetting 37 Burhan Uddin, Karachi
- 38. Epidemiology Approach in CommunitySetting 38
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