I recall the great anticipation of my first class in medical epidemiology where we learned the principles of incidence, prevalence, point prevalence, transmission of disease, vectors, hosts, fomites, and so on. The class seemed daunting and unimaginably boring. Despite this initial impression, the instructor had an unmistakable aura about him that was accentuated by his gold-rimmed, rounded spectacles. He was a sage US Army Colonel and physician who specialized in “tropical medicine.” You could easily imagine him wearing a British khaki uniform, complete with Bermuda shorts and a pith helmet, tromping around in faraway places.
Unexpectedly, the instructor began the session with a story about the “Broad Street pump.” This single story ignited and held my interest in the concepts of medical investigation, the basics of epidemiology, and preventive medicine, even to this day.
In 1854, the English physician (the father of epidemiology) John Snow discovered the link to the lethal cholera epidemic, which killed tens of thousands of people in England between 1831 and 1854. Although the etiology of cholera was unknown, the strong belief at the time was that it was caused by breathing vapors, a “miasma,” or foul air. In 1854, the London suburb of Soho was the epicenter of an endemic cholera outbreak that led to 500 deaths in 10 days.1–3 Snow used what are now known as epidemiologic principles to investigate the causation through interviewing people (cases) who were stricken with cholera and those who were not. He compared the incidence and prevalence of those who lived in the “surveillance” area with and without the disease. Snow discovered that the commonality between those with the disease was where they drew their drinking water—the Broad Street Well.
One major source of evidentiary contamination was a case of a mother washing diapers and dumping the waste into a leaky cesspool, just 3 feet from the Broad Street pump, which was probably the tip of the iceberg. Through meticulous recordkeeping and epidemiologic interviewing techniques, Snow was able to triangulate commonalities and establish causation. He observed that all of its victims drew their drinking water from the same well. Snow removed the pump handle, and the epidemic ended. The infamous Broad Street pump is now a memorial to the triumph of medical epidemiology. Although cholera was endemic to London in the 19th century, its original reservoir was in the Ganges Delta in India. And during the 20th century, 6 subsequent pandemics killed millions of people across all continents. The current (seventh) pandemic started in South Asia in 1961 and reached Africa in 1971 and the Americas in 1991. Cholera is now endemic in many countries. We now know that cholera is spread by contaminated water and not from person to person. And finally, we now have vaccines for cholera.1–3
This month’s continuing medical education activity on page 35 is a primer on medical intelligence in wound care. Wound care professionals who operate at the point of service need to develop core competencies in gathering intelligence data about incidence and prevalence of pressure ulcers. In this case, the intelligence is in the form of gathering epidemiological information to be used by the institution providing and improving care, to feed the data to interested parties in general, and, in particular, to payers, hospital credentialing, and accreditation organizations. In addition, the use of prevalence and incidence data can be used to implement the plan-do-study-act cycle for quality improvement and clinical management, patient care, and educational continuous quality improvement plans, especially as we move into an area of accountable care and pay for performance.4
Recently at the 27th Anniversary Clinical Symposium several of the poster winners included epidemiologic studies demonstrating the importance of using statistical measures in wound care and reducing the incidence of new pressure ulcers in a given hospital organization. One case used a multinational study to illustrate the applicability of the use of data to institute prevention programs and improve patient outcomes. Medical surveillance in wound management is a strategy that is as important as any.
Richard “Sal” Salcido, MD
1. Newsom SW. Pioneers in infection control: John Snow, Henry Whitehead, the Broad Street pump, and the beginnings of geographical epidemiology. The J Hosp Infect 2006; 64: 210–6.