Home 
Contact 
Profile 
Videos 
Presentation at a course held online via Zoom on March 21, 2021. By Professor Omar Hasan Kasule Sr. MB ChB (MUK). MPH (Harvard), DrPH (Harvard) Chairman of the Institutional Review Board
- The word epidemiology is derived from Greek. Epi = among, demo = people, and logos = study.
- Epidemiology is both a methodology (for example study design) and substantive information (for example the epidemiology of coronary heart disease).
- Being a methodological discipline epidemiology does not have a coherent specific subject matter. It is not a definable body of knowledge. It is a methodology of how to get knowledge.
- Epidemiology studies health and disease in a community or a group of individuals rather than an individual.
- Epidemiological conclusions are based on comparison of groups. It is important to select the groups carefully to avoid bias.
- Epidemiology is the study of the distribution and determinants of disease and injury frequency in human populations.
- Epidemiologic study of disease distribution includes study of disease occurrence in terms of time, place and persons affected (age, sex, race, socio-economic status, occupation, and culture).
- Epidemiologic study of disease determinants includes factors that cause or contribute to disease occurrence.
- Epidemiology also includes study of the natural history of disease (antecedents & consequences) with view to prevention.
- Epidemiology also includes study of all phenomena that are related to disease causation and prevention.
- Epidemiology can be visualized as 2 types of triads. The first triad is a study of the agent, host, and environment of a disease. The second triad is study of the time, place, and persons involved in disease.
- The primary goals of epidemiology are prevention, control, and in rare instances eradicate disease and injury.
- Basic issues of epidemiology are: definition, diagnosis, prognosis, measurement, transmission, determinants, natural history, treatment, prevention and control, as well as health care research.
- 1st era: Epidemiology started as a study of epidemics.
- 2nd era: Epidemiology became study of infectious disease.
- 3rd era: Epidemiology was later extended to study of non-infectious diseases.
- 4th era: Epidemiology has now become a methodological discipline.
- 5th era: Epidemiology is even beyond study of disease.
- Until the mid-19th century M, epidemiology was only a study of epidemics. Epidemics of infectious disease were frequent and epidemiologists were pre-occupied with them.
- The epidemic prevalence of a disease is markedly higher than the non-epidemic prevalence.
- Epidemics may be acute such as cholera or slow such as lung cancer or coronary heart disease.
- Epidemiology can be defined as a study of epidemics if we consider chronic diseases like coronary heart disease and cancer as slow epidemics.
- The last quarter of the 19th century witnessed many new discoveries in the microbiological disease etiology. The microbiological agents, their vectors, and modes of transmission were described.
- Disease patterns were studied and it was found that disease was not randomly distributed in the population and that there were factors determining the local patterns of distribution.
- Epidemiology in that era was closely related to microbiology.
- The book on infectious disease epidemiology is not yet closed. New agents of disease are being discovered. There is change in pathogenesis and transmission of known agents. Changes in human behavior led to new patterns of disease transmission.
- New and recent discoveries are uncovering an infectious basis for chronic diseases that were considered non-infectious before.
- Studies in the period after the Second World War showed increasing incidence of chronic diseases due to an older population and relative decrease of infectious disease.
- Study of chronic diseases became a major pre-occupation of epidemiologists in Europe and America.
- Epidemiologists studied risk factors, the natural history, and preventive interventions.
- In the chronic disease era use of the statistical methodology became more wide-spread.
- Epidemiology in the chronic disease era was closely related to study of cancer which is the most serious of the non-communicable diseases.
- The term chronic is a misnomer because both infectious and non-infectious diseases can be chronic. It is better to talk about communicable and non-communicable diseases.
- Epidemiology has now become a purely methodological tool applied to several disciplines.
- Epidemiology in the field of health and disease is applied to communicable and non-communicable diseases.
- Epidemiology is used in the fields of health policy & management, health quality assurance, health planning and health evaluation.
- Epidemiology is finding increasing application in the social and human sciences.
- Epidemiology will have to contend with new challenges and frontiers: global warming, ozone depletion, environmental pollution, demographic changes, emerging infections, and re-emerging infections.
- Global warming will lead to increase of disease vectors because of higher ambient temperatures, melting of the polar ice cap leading to rising sea levels thus disrupting coastal ecosystems with yet unknown effects on health, affect the weather patterns and agricultural production.
- The depletion of the ozone layer will allow ultra-violet radiation to reach the earth and cause damage to human, animal, and plant DNA.
- As countries develop industrially, their population structures change. They get more elderly dependent citizens and fewer young workers to support them. Rural to urban migration is creating megacities that have many social problems.
- New infectious diseases are appearing: HIV, Ebola, Hantavirus, and Lyme disease.
- Infectious diseases that had been defeated are re-emerging: dengue and tuberculosis. Drug resistance is increasing.
- Epidemiology has expanded so much and has involved itself in so many fields of endeavor that it risks losing its original identity without at the same time picking up a new identity. This may result in its disappearance as a coherent discipline.
- As a scientific methodological discipline, epidemiology need not be confined to its public health origins. As a methodological discipline it can find applications in the clinical as well as health policy fields.
- The divorce of epidemiology from public health should be blamed on modern public health practitioners who have moved the field from the narrow confines of scientific investigations to social and policy issues that are more political than scientific.
- The pressure to be politically correct has also forced epidemiologists to present and interpret their evidence in ways that are considered appropriate. They have had to do this in order to have the audience of the public and the policy makers.
- Another force pulling epidemiology from its scientific base lies in its very nature. Over the decades we have been able to decrease the risk of disease by preventive measures before we understood the causal chain in full.
- The argument is that the epidemiologist should be more involved in the field with social and other interventions against disease rather than spend time doing careful but slow-yielding studies to understand causal mechanisms.
- The possibility of dividing the discipline into basic epidemiology emphasizing causal research and applied epidemiology emphasizing intervention against disease in the field can be considered but would be difficult to realize in practice.
- The emerging field of molecular epidemiology may resolve many of the dilemmas discussed above.
- The availability of a lot of data online is posing a new challenge to epidemiology.
- Exponential growth in the quantity and sophistication of statistical techniques also poses a novel challenge to traditional epidemiology. System analysis and meta-analysis are powerful tools that enable deeper understanding of phenomena but which may lead to loss of sight of the simplicity of epidemiology.
- Qualitative epidemiology describes the disease patterns as attributes without quantification.
- Quantitative epidemiology uses exact numerical data.
- There was a relatively slow development of the epidemiological methodology when the discipline was qualitative. This changed rapidly when epidemiology became quantitative and started being treated as a serious science.
- Epidemiological data can be obtained by observation of human phenomena (observational epidemiology) or by experimental intervention (experimental epidemiology).
- Observational epidemiology can be descriptive or analytic. Descriptive epidemiology describes the burden of disease and associated characteristics. It is the extension of demography into medicine. Analytic epidemiology studies causal relations between exposures and disease.
- Experimental epidemiology involves intervention against a disease phenomenon and assessment of the effects of the intervention. It is in essence analytical.
- We can talk of theoretical (basic) epidemiology and applied epidemiology. Those involved in theoretical epidemiology consider themselves the elite of the discipline who do not dirty their hands with data. They tend to work on the mathematical and philosophical aspects of the discipline which with time find application in the field.
- Epidemiological knowledge can be applied in various settings such as hospital epidemiology, clinical epidemiology, disease screening epidemiology, drug epidemiology, radiation epidemiology, genetic epidemiology, nutritional epidemiology, environmental epidemiology, occupational epidemiology, geriatric epidemiology, and public health epidemiology.
- Theoretical epidemiology deals with the mathematical and statistical methodology used in data analysis and data interpretation.
- Descriptive epidemiology describes the patterns of disease occurrence in terms of place, time and person.
- Analytic epidemiology seeks to discover the underlying causes of diseases.
- Public-health epidemiology is a general term for the study of public health and preventive medicine which includes risk factors, outcome, treatment, and prevention of disease.
- Clinical epidemiology is concerned with the diagnosis and management of disease as well as assessing its prognosis. It can alternately be called clinical decision making.
- Hospital epidemiology deals with nosocomial infections and other aspects of hospital operations that can be studied using epidemiological methodology.
- Drug or pharmaco-epidemiology studies phenomena of adverse reactions and side-effects of drugs.
- Genetic epidemiology studies the patterns of inheritance of disease from the parents and how genetic and environmental factors interact in the final pathway of disease causation.
- Molecular epidemiology will revolutionize all our understanding of diseases, their causation, classification, and treatment.
- Occupational epidemiology studies diseases due to exposure to hazardous material or working conditions in the work-place.
- Environmental epidemiology studies the impact of air, water, and soil pollution on health.
- Clinical sciences
- Demographical sciences
- Data and information sciences
- Behavioral sciences
- Environmental sciences
- Clinical medicine
- Public health
- Risk and actuarial sciences
- Hippocrates made the first recorded epidemiological observations.
- Galen introduced a theory of disease based on constitutions, humors, and temperaments.
- John Snow (1813-1858) recognized the importance of field epidemiology in his study of the London cholera.
- William Budd (1811-1880) described the spread of typhoid due to ingestion of infected material from patients.
- William Furr realized that cycles of epidemics could be described mathematically and contributed a lot to vital statistics.
- Major Greenwood (1880-1949) was chief of epidemiology and vital statistics at the London School of Hygiene and Tropical Medicine and worked on models of epidemics