Trends in Epidemiology
We like to think of the development of science as following a straight path. First, some of our primitive ancestors made an astute observation, such as how summer rain storms are often accompanied by thunder and lightning. This led to the hypothesis that a god on Mount Olympus was throwing things at us, which was later replaced by a correct theory (correct because it’s what we believe today). Based on our improved knowledge, we are now able to intervene, such as by seeding clouds to produce rain when we want it or to prevent tornados when we don’t want them. Thus we move from observing and hypothesizing (classical epidemiology) to intervening and improving (clinical epidemiology).
Comforting as this picture is, it doesn’t correspond too closely with reality. As we’ll see in the next chapter, epidemiology did in fact start with observation and hypothesis generation, about the time when the major health threats were infectious diseases: tuberculosis (TB), cholera, influenza, and the like (the Age of Pestilence and Famine). Some time during the middle of this century in the Western world (and about now in the rest of the world), we entered into the first epidemiologic transition, which could be called the Age of Receding Pandemics (a term we’ll define in the next chapter), when we thought most infectious diseases were either completely wiped out (e.g., small pox) or contained (e.g., polio, TB). This was followed by a second transition into the Age of Degenerative and Man-made Diseases (e.g., cancer, cardiovascular problems) because a significant portion of the population is now surviving beyond the reproductive years. We could also call it the Age of Useful Interventions as we learn which medications, surgical treatments, and “lifestyle” interventions actually produce more success stories than failures.
So far, so good; epidemiology is following the pattern that we would like to see. But at the same time that we’re moving into this latest age, we are suddenly rediscovering outbreaks of infectious diseases in the developed world. Within the past few years, a new Hantavirus outbreak occurred in the mid-western United States, and it took all the tools of the classical epidemiologists to trace it to the droppings of mice. Similarly, TB, which we thought was almost completely wiped out through a combination of better drugs and improved housing, has come back in a more treatment-resistant form to attack people living in the city cores and especially people with compromised immunologic systems as a result of human immunodeficiency virus (HIV) infection. So it’s back to making observations about acute infections and testing hypotheses.
In many ways, this is similar to the prediction made in about 1900 by an eminent professor who decreed that, given the natural history of physics, approximately 3 more years of research would suffice to solve all the remaining problems. His major mistake was underestimating the survival instinct of researchers. Epidemiologists have been equally adaptive, moving from infections to chronic diseases to drug trials. They have been just as adaptable by moving back to studying infectious and chronic diseases as these have reemerged as major problems.
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| 5476. | Streiner DL, Norman GR. PDQ Epidemiology. 2nd ed. Hamilton, Ontario: BC Decker Inc.; 1996. |
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