In yet a new first part of an ongoing series of posts, I will try to blog about concepts of epidemiology that will be covered on the comprehensive examinations (hereto referred to as “comps”). In the interest of efficiency and time, I’ll only briefly cover concepts and ideas I feel that I do not quite remember well or understand. For example, if asked to recall the five rubrics of epidemiology (quantity, location, causes, mechanisms, prevention and control), it would not be difficult, thus I should not waste my time blogging about them.
Today, I will cover concepts from EPI 810 – Introductory Epidemiology. In subsequent posts I may continue to discuss issues of EPI 810, or jump around to other courses.
- Epidemiology comes from Greek, ‘epi’ meaning ‘upon, among’, ‘demos’ meaning ‘people’, and ‘ology’ or ‘the study of’. It literally means ‘what falls upon the people’.
- Epidemiology is defined by Last as “the study of the distribution and determinants of health related states and events in the population and the application of this study to control of health problems“. It is important to note that this definition emphasizes epidemiology’s concern with quantity/location, causes of disease, a focus on the population, and the importance of prevention/control.
- It is important to remember the difference between a vector and a vehicle in the transmission of infectious disease. A vector is an animate carrier, such as a mosquito, fly, or even human being. A vehicle is an inanimate carrier.
- It is likely that JCA will ask about Geoffrey Rose’s distinction between “causes of cases” and “causes of incidence“. Basically, the cause of disease in an individual (cause of a case) may not be the same as the cause of disease in a population (cause of incidence). They address different question and may have different answers.
- Another important point in the Rose article worth remembering are the pros and cons of the ‘high-risk strategy‘ of disease prevention/control and the ‘population strategy‘. I may return to this idea in the future, but for now, remember that the high-risk strategy has a large benefit for those individuals, but low for the population, and does little to impact the root cause. Conversely, the population strategy can have the largest impact on the population, but may have very little individual benefit.
- Also remember Rose’s observation that “a large number of people at a small risk may give rise to more cases of a disease than the small number who are at a high risk.”
- Recall that the four major methods of person-to-person transmission are:
- Direct contact – <3' without an intermediate object
- Indirect contact via a vehicle (e.g., bacteria on a tooth brush)
- Indirect contact via airborne dust or droplet (>3′)
- Indirect contact via a vector
- Remember that a contagion is ‘a mechanism of disease transmission that must be identified as an after-effect of a prior effect‘.
Unfortunately, I have to end this post prematurely. The PowerPoint slides from JCA on EPI 810 were removed from the Angel site, and I have no other source of information for the content.