The book, The Ghost Map: The Story of London's Most Terrifying Epidemic-and How It Changed Science, Cities, and the Modern World by Steven Johnson tells the story of the London cholera epidemic in 1854 from the perspective of individuals who were succumbing to the disease, the community affected, and the city of London as a whole.  Johnson shows how a single pump, mixed with deplorable sewage and waste infrastructure, brought about a deadly epidemic.  Johnson also tells the story of Henry Whitehead and John Snow who both, coming from completely different backgrounds, tried to combat the epidemic, quell the fears of a community, and explain how cholera was being transmitted.  This was not an easy task considering the medical establishment blamed "miasma," or bad air and smells, instead of relying on scientific evidence that came from Dr. Snow.  Johnson details how Snow's perseverance led him to bring epidemiology, and not superstitions, into the forefront of public health.  

One of the main purposes for Johnson writing this book was to describe how London, as a modern, growing city, became so vulnerable to a cholera epidemic, and almost any infectious disease for that matter.   He lays out the negative, but also highlights positive, ramifications of rising population density, cultural convergences, and urbanization.  He stresses lessons to be learned about taking science into consideration when organizing cities in order to prevent conditions from compromising a population's health.  Finally, Johnson aims to put the London cholera outbreak in a historical context so the public can see a prime example of how the scientific community learned about the emergence of diseases, theories of disease transmission, and the organization of public health infrastructure. 

The obvious environmental health issue addressed in The Ghost Map is the disease cholera, otherwise known as the bacterium, Vibrio cholera.  Cholera is an infectious disease spread through ingesting contaminated food, liquid, or ingesting the bacteria through other means.  Having the bacteria and then spreading it through excrement is the main hazard that puts populations at risk for the disease.  Cholera is most often spread through feces entering a public water source and then people using the contaminated water for drinking, washing, or preparing food.  Water is most likely to be contaminated when waste and garbage disposal is inadequate, when people live in crowded living situations, or when sewage systems are not functional, properly built to handle large populations, or not maintained. 

In the case of London in the 1800s, the waste disposal systems were either completely nonexistent or not able to handle the amount of use the bourgeoning population of the city demanded.  There was also no water treatment system or reliable way to get clean, fresh water.  The living conditions in the city especially lacked cleanliness and order for the urban poor.  They would most often dump human waste into huge cesspools (that were not regularly emptied) or right onto the street or other people's property.  People also lived in very tight quarters, an easy breeding ground for infectious diseases. 

The source of the particular cholera outbreak that occurred late into the summer of 1854 is thought to have been originally caused by the disposal of a diaper of a baby who was sick with the disease, leading the Broad Street well to become contaminated with the bacteria.  When people got water from the pump and then drank it, or washed food in the water, they were exposed to the bacteria and at risk for developing the disease and further spreading it to others. 

The consequences of cholera are downright scary.  First off, at the time of the London outbreak, hardly anything was known about how to treat or cure the disease, so it had high mortality and case-fatality rates.  It was also a quick killer; once you were exposed it could be just a day or two before you succumbed to the disease.  The main symptoms of cholera are a stomach ache, frequent and debilitating diarrhea, vomiting, cramping, and thirst.  Your body shuts down from dehydration, you become cyanotic, and then you die if not treated properly. 

Johnson used many different sources for writing The Ghost Map.  Most were historical backgrounds and writings on London during the time of the epidemic, biographies and other information about John Snow's work and the life of Reverend Whitehead, and information about this, and other cholera outbreaks.  This was all supplemented by primary documents of the times, particularly some by famous authors who lived in or visited the city, but also first-hand accounts of the actual epidemic.  These primary documents included writings by Charles Dickens, George Eliot, Stephen Gould, and Jane Jacobs. 

By no means is cholera a disease of the past.  A study published in April 2009 in the American Journal of Tropical Medicine and Hygiene describes a retrospective case-control study of a cholera outbreak in 2005 in a refugee camp in Kenya.  [See: Shultz A, Omollo JO, Burke H, et al.  Cholera outbreak in Kenyan refugee camp: risk factors for illness and importance of sanitation.  Am J Trop Med Hyg.  2009;80(4):640-5.  Link: http://www.ncbi.nlm.nih.gov/pubmed/19346392?ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

The purpose of the study was to identify what the risk factors for contracting cholera were and how, in the future, interventions might be used to prevent and treat the disease.  Shultz and colleagues describe why inhabitants of refugee camps are extremely vulnerable to diseases like cholera because of the unstable and temporary nature of the living conditions.  The researchers found that being a recent arrival to the camp was associated with a significantly higher risk of being infected compared to residents who had been there for longer periods of time.  Those residents who shared a latrine with three or more other households were also at a higher risk.  The study also showed that protective factors included storing water in the home and sealing or covering it while not in use and using soap during hand washing.  The study concluded that improving sanitation, applying interventions to protect drinking water, and targeting prevention messages to newcomers to the camps would be the most effective in preventing future cholera outbreaks. 

After reading both The Ghost Map and this case-control study on a cholera outbreak in a Kenyan refugee camp, my view of the disease has definitely changed.  First of all, the main -- and most shocking -- difference between the setting of the disease in the book and in the study is time.  The events in The Ghost Map took place about 150 years ago; the outbreak studied in this article took place in 2005.  This is especially noteworthy because part of the point of the book was that because of the 1854 outbreak in London, the epidemiological pattern of cholera was identified and elsewhere around the same time, the bacteriological cause was also uncovered.  Once John Snow mapped his 'ghost map' and the Broad Street Pump was shut down, the mystery of cholera was all but solved.  Yet centuries later the disease, with the same horrible symptoms, is still a killer. 

The difference now is who is affected.  Cholera outbreaks are no longer studied in London or pretty much anywhere else in the developed world.  The cholera that you hear and read about is in the developing world.  It is affecting largely the same vulnerable populations -- the poor, urban dwellers -- and the same risk factors are the culprit -- lack of sanitation systems and waste disposal, and crowded living conditions -- but these conditions tend to exist only in the 'third world'.  This study in particular looked at a very vulnerable population even within a developing population.  I would imagine that the squalor described in The Ghost Map of London during the 19th century is not unlike what refugee and internally displaced persons camps in Africa are like; all conditions which are perfectly ripe for spreading cholera.  The only problem with this reasoning is that even though the conditions are perfect for cholera (which is a problem in itself), the scientific and public health communities now know how exactly cholera works, how it is transmitted, and spread, and how it can be treated or how it kills.  With this knowledge, one would think that cholera outbreaks, like the one in the study in Kenya, or in Zimbabwe, should be more easily prevented or at least controlled.  I applaud the article for not just identifying risk factors for contracting cholera in this refugee camp, but also for making recommendations for interventions about how to prevent future outbreaks and how to apply what was learned in the study to other similar sets of circumstances and living situations. 

What struck me most about comparing the two articles was that it doesn't matter what century you contract cholera in, it will still be a horrendous disease -- time hasn't changed that.  The cholera bacteria is just as deadly if not treated now as it was in London in 1854, and when outbreaks occur today in developing countries, the lack of health care infrastructure makes finding a cure or treatment just as difficult as it was back then when none was known.  Symptoms described in the study such as water diarrhea were also the symptoms that Reverend Whitehead and John Snow saw consume citizens in the  Golden Square community of London. 

The lessons that Johnson tries to get across in The Ghost Map about organizing cities, controlling population and urbanization, taking scientific evidence into account, and using reason as a preventive measure need to be heeded more in current times.  If John Snow were alive today he would surely say that the first problem that needs to be tackled in developing countries is constructing proper water and sanitation systems and making sure people have uncontaminated water sources to drink and eat and that human waste is dealt with properly.  Although this is a daunting task considering the infrastructure and resource situation in most of the developing world, having safe drinking water and a sewage and waste disposal system would not only prevent cholera outbreaks, but also improve the living situations for millions of people. 

Although there are clear differences between the story by Johnson in The Ghost Map and the situation in Kenya researched in the study I read, the disease is the same, the symptoms are the same, and the effects are just as devastating.  The knowledge we have gained about cholera, starting with John Snow and continuing for the next 150 years, should be more rigorously applied to preventing outbreaks from occurring anywhere in the world today.