John Snow and the Story of the Broad Street Pump 

From discovering the causes of polio and smallpox to controlling epidemics all around the world, epidemiologists have been behind many of our current advancements in public health. While the field of epidemiology now encompasses a wide range of skills and methods, its origin is commonly traced back 1 to a single story; the tale of John Snow and the Broad Street pump.

Snow was born in England in 1813—a time when the prevailing notion behind disease transmission was the “miasma theory.” 2 According to this theory, diseases were spread through particles from decomposed matter that would then become part of the air. Snow, who had survived a number of cholera epidemics in his childhood before pursuing a career in medicine, was 3 cynical about this elegant but incorrect theory. However, it was not until the cholera epidemic of 1854 that he was able to acquire insurmountable evidence showing that cholera was caused by something other than “bad air.”

Within the first two weeks of September, 1854, over 500 people had mysteriously died 4 of cholera. Those who had died were all within 250 yards of the Cambridge Street and Broad Street intersection in the Soho district of London. Snow began analyzing the addresses of those who had contracted the disease. He found that, of the hundreds of cases of cholera near Soho, 5 and all but ten involving people who lived near the contaminated pump on Broad Street. Of the remaining ten cases, five involved people who preferred the water from the Broad Street pump and three involved children who went to school near the Broad Street pump. Snow’s research was too compelling for the local council to ignore: they eventually removed the Broad Street pump from service, 6 affectively ending the cholera outbreak in Soho.

  7 Today, epidemiology is considered a basic science of public health. It is a quantitative discipline built on probability, statistics, and research 8 methods, a method of causal reasoning based on developing and testing hypotheses, and a tool to promote and protect the health of the public. Examples of applied epidemiology include monitoring reports of communicable diseases in the 9 community; and tracking down the cause of a food- borne outbreak. While many epidemiologists work for health departments at the local and state levels, a number are also employed by colleges and universities. 10 In 2012, the median wage for epidemiologists in the United States was around $60,000, though this number was substantially larger for those working in the state government. For those interested in pursuing a career in this field, the prospects also look bright, 11 but employment is projected to grow 10 percent between 2012 and 2022.