Cholera: You Know Nothing, John Snow

Aliases: cholera

Cholera moves in lockstep with extreme poverty; the pathogen capitalizes on the frailty of poor infrastructure to spread. Tragically, that means it is incredibly common around the globe. Worldwide, there are an estimated 1.4-4.3 million cases and 28,000-142,000 deaths from the disease each year. Its short incubation period (the time between a person contracting the disease and being able to pass it to someone else) of 2 hours to 5 days means that it can appear to emerge out of nowhere in explosive epidemics. And its effects are devastatingly lethal; if left untreated, cholera can kill within hours.1

Despite how truly terrible it is, cholera has had some positive effects on society. The disease has become iconic in epidemiology, the study of the patterns, causes, and effects of disease, after inspiring the birth of the field. During a major cholera epidemic in London’s Soho neighborhood in 18542, Dr. John Snow (yes, really) painstakingly mapped deaths caused by the disease and documented the household water usage. He personally visited 658 homes to determine their water source3, systematically compiling evidence to support his theory that cholera was water-borne and combat the prevailing “miasma” theory, which suggested that cholera was spread by “bad air” containing particles of decomposed matter.2

Eventually the data became overwhelming (all the deaths had occurred within 250m of one street intersection), and indicated that the source of the cholera was the now infamous Broad Street pump. Snow succeeded in having the handle of the pump removed3, and the epidemic came to a halt. Yet despite the fantastic results, doubts lingered about Snow’s theory. As he himself admitted, without knowing the cause of the disease he couldn’t prove that the removal of the pump handle had stopped disease spread; the epidemic could have been waning anyway for any number of reasons.2 Snow’s work was unpopular with the medical community and his ideas were widely rejected.3 He was only vindicated posthumously, when Robert Koch identified Vibrio cholera (the bacteria that causes cholera) in 1885.2

Education saved John Snow’s groundbreaking work. It was lost to obscurity until the 20th century, when it was revived by WH Frost, the first professor of epidemiology at the Johns Hopkins University School of Hygiene and Public Health. Frost edited a reprint of Snow’s book on cholera in 1936 and proceeded to popularize it in his classes. He used Snow’s efforts to combat cholera as a classic case study of epidemiology in action, and this view spread throughout academic circles globally.4 Today John Snow is acknowledged as one of the fathers of epidemiology, and he and the Broad Street pump have become icons.2,4

Come at me, bro.

Cause: Cholera is caused by ingesting the bacteria Vibrio cholera in either contaminated food or water. It affects all age groups, afflicting adults and children. When it comes to cholera, humanity may be its own worst enemy; humans are a main reservoir for the disease and global warming (which is at minimum partially our fault) creates favorable environments for the bacteria. But it is our predilection for inequality that may be our greatest gift to the disease; it is especially common in areas of poverty or crisis, where there is generally poor infrastructure.1

Consequence: 80% of cases are asymptomatic. That means that 80% of people who contract cholera experience no ill effects, although they can still potentially infect others. Of those that develop symptoms, 80% have a mild to moderate course of the disease; only 20% are severe cases that can be fatal, experiencing acute watery diarrhea and severe dehydration.1

Cure: Finally some good news: cholera is amazingly responsive to treatment. Up to 80% of cases can be successfully treated simply with rehydration salts and with proper treatment the case fatality rate plummets below 1%. There are also two WHO pre-qualified oral vaccines. But although the disease is treatable, the best protection against cholera is prevention. Safe water and sanitation are critical to long-term control and prevention. That means piped water and treatment plants, water filtration and safe storage in homes, and safe sewage and waste disposal systems. Here’s the rub: this kind of systemic change demands economic development to offset the significant initial investment and high maintenance costs.1


  1. Cholera. World Health Organization. July 2015. Web. 17 September 2015.
  1. Kukaswadia, A. John Snow− the first epidemiologist. PLOS Blogs. 11 March 2013. Web. 17 September 2015.
  1. Paneth, N. 2004. Assessing the contributions of John Snow to epidemiology: 150 years after removal of the Broad Street pump handle. Epidemiology, 15: 514-516.
  1. Vandenbroucke, JP, HM Eelkman Rooda, & H Beukers. 1991. Who made John Snow a hero? American Journal of Epidemiology, 133: 967-973.

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Primary Care in America: Falling Fast

Primary care physicians are critical; adding just one primary care doctor per 10,000 people decreases annual deaths by 5.3% and reduces health care costs. Yet of the 800,000 practicing physicians in the United States, only 32% practice primary care, and this number is expected to drop. It is estimated that a mere 18% of current medical school graduates will go into primary care, and that by 2016 the number of retiring primary care physicians in America will exceed the number entering the field5. This is –to put it mildly—concerning. The situation seems to be the result of an unfortunate mismatch between supply and demand that is playing out in American medical schools.


Demand for primary care is on the rise. The silver tsunami, the vast wave of Baby Boomer retirements that began in 2011, is expected to continue at a rate of 10,000 per day until 2029, tallying up a total of 80 million retirees in less than 20 short years. This includes doctors, and they are leaving behind an increasing number of empty posts throughout the US healthcare system. The Affordable Care Act (ACA) will also ratchet up demand for primary care physicians by extending insurance coverage to an additional 32 million Americans by 2019. However, even without the ACA, the national primary care workload is expected to increase by 29% between 2005 and 20255.


On the other hand, the supply of primary care physicians is diminishing. Starting in 1980, a series of reports predicted a physician surplus in the US4. As a consequence, while the American population continued to increase, the number of students graduating from medical school remained essentially static from 1975 to 2000 (between 15,000 and 16,000 per year)5. It’s now expected that the US will have a 30% physician deficit by 20201. In addition to this bottleneck, a compensation gap emerged, with the average income for specialties far outstripping primary care. The average income for specialties has increased 37.5% since 1998, while the average income of primary care physicians only rose 21.4%, not even enough to keep pace with inflation5.

It is utterly unsurprising that doctors are looking for appropriate compensation and financial security. The demands of their profession are herculean, and the trials start early. Admission to medical school in the US requires a bachelor’s degree, admission testing (the infamous MCAT), medical, leadership, and volunteer experience, as well as an excellent grade point average, personal statement, and letters of recommendation. Once in medical school, students receive an average of 21 hours of direct instruction per week for the first two years. In the third and fourth years, which are dedicated to clinical clerkships, that number jumps to 38-47 hours of direct instruction each week. To add insult to injury, after this fairly arduous education, the average medical student in the US will graduate with more than $100,000 in debt2.

And their education is actually far from over. In the final year of medical school, students apply for positions in one of the 4,100 graduate medical education (GME) programs for further training. They can expect to spend the next 3-7 years as a resident in a GME, after which they can choose to gain additional training in one of the 4,800 specialty fellowship programs in the US. Residents and fellows are wildly overworked. Until 2003, there were no restrictions on resident work hours and they routinely worked 80-100 hours per week. Thankfully, that has changed. As of 2011, first year residents work (a still ludicrously high) maximum of 16 consecutive hours, and no more than 24 consecutive hours in subsequent years. Residents take board certification exams, which must then be retaken every 6-10 years. Typically, physicians are also required to log 50 continuing education hours each year2. In medicine, there is truly no rest for the weary.

primary care
I’ll be here all day. Literally.

Primary care

Medical schools are trying to fill the gap. Since 2005, 75% of medical schools have undergone curriculum reform3. With the aim of expanding the medical student body by 30% (5,500 students per year) to match the projected physician deficit, many schools are increasing enrollment, and 12 new medical schools are under construction. This will have a profound effect on medical education. Teaching more students will demand greater numbers of faculty, more facilities and equipment. Clerkships may shift from the classic academic model to a preceptorial model, where students are assigned to one clinician and accompany him/her throughout the day. It could negatively impact student-professor relationships, and the heightened demand for teaching may reduce professors’ ability to simultaneously run robust research programs. There is also some concern that the applicant pool will be exhausted and raising enrollment will decrease the quality of applicants.

Several other possibilities are also being pursued. There are initiatives for incentivizing (paying more for) primary care. Primary care may come to rely more heavily on non-physician practitioners (NPP), physician assistants and nurse practitioners, the fastest growing sector of primary care. NPP are also more likely to work in underserved areas and with underserved populations. The growing need may also be met by international medical school graduates (IMG), foreign physicians who practice in America. In 2011, IMGs accounted for 40% of primary care residency positions in the US5.

Increasing the number of primary care physicians is essential to the success of both the American healthcare system as a whole and the Affordable Care Act (ACA). Simply put, people need doctors. Even if it succeeds in its sweeping mission to radically expand insurance coverage, the ACA will fall flat if there are no primary care doctors accepting new patients5. Closing the 30% physician deficit while balancing specialization with primary care will be no easy task, and the stakes are high. The medical education system will bear the brunt of this challenge; let’s hope it’s a quick study.


  1. Bonaminio, GA, SB Leapman, JJ Norcini, RM Patel, & DM Elnicki. (2008). The educational realities of increasing medical school class size. Academic Medicine, 83(10):S101-S104.
  1. Dezee, KJ, AR Artino, DM Elnicki, PA Hemmer, & SJ Durning. (2012). Medical education in the United States of America. Medical Teacher, 34:521-525.
  1. Drake, RL. (2014). A retrospective and prospective look at medical education in the United States: trends shaping anatomical sciences education. Journal of Anatomy, 224:256-260.
  1. Gevitz, N. (2009). The transformation of osteopathic medical education. Osteopathic Medicine and Medical Education, 84(6):701-706.
  1. Schwartz, MD. (2011). Health care reform and the primary care workforce bottleneck. Journal of Gernal Internal Medicine, 27(4):469-472.

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