Medical geography

August 1854. London was experiencing an outbreak of cholera. People were dying in alarming numbers. A physician, Dr John Snow, did some very innovative investigating. He plotted cases of cholera on a map of London, using dots to show where the cases were occurring. Then using interviews with local people and sophisticated statistical methods, he achieved a breakthrough that was to become a famous story in geographical history and help stimulate a field of modern geography called medical geography. His discovery was that the cases were centered around a water pump on Broad Street in the Soho area of London. He further figured out that cholera was a water-borne disease and that contaminated water was the cause of the spread and not air, as people had believed.

He had that pump’s handle removed and the cases came down. The problem had been that the well from which that pump was drawing water was contaminated by raw human sewage from a cesspit (where human waste accumulated instead of being flushed out).

Every epidemic features a contagious disease. Contagious diseases spread in many ways. Cholera spreads through the medium of contaminated water. It does not require person to person contact.

When the Human Immuno-deficiency Virus (HIV) outbreak occurred and discovered in the USA in 1982, one of the first questions was a geographical question: where is it occurring? It was initially discovered to be in San Francisco. As cases of its occurrence started getting reported, that geographical question became more and more important. It helped address two other questions: (1) how was it spreading, and (2) where did it originate?

Geographers got to work quickly and soon were able to report geographical patterns of the HIV’s movement. As the geographical questions were answered, it became increasingly clear how it was spreading (direct person-to-person contact, exchange of body fluids, contaminated blood and organs being transplanted). This is called contagious diffusion in geography.

A geographical pattern of another kind also emerged. This was shown in a very interestingly animated map that showed how AIDS (Acquired Immuno-Deficiency Syndrome, the condition that HIV causes) spread in the USA from 1985–1997. The map shows the first appearance of AIDS in major cities that are also important hubs for international travel. Then, over time, the disease appears in other smaller and smaller places. You can see this animated map and if you keep an atlas handy, you could easily figure out the main cities where clusters of AIDS cases appear. This pattern shows what geographers call cascade diffusion — where a disease spreads from top-tier places (high population, great transportation connectivity with other places, large size, culturally and financially important, and so on) to smaller and smaller places (lower population, less transportation connectivity, etc.).

Even globally, this pattern can be deduced for many parts.

Geography also helped understand how the HIV, the virus that causes AIDS originated as SIV (Simian Immuno-deficiency Virus) in a species of monkeys in humid, tropical Africa. From the monkeys, the virus jumped across species to humans (humans there used to consume the meat of this monkey as part of their diet). Rivers connected human beings because they traveled on these rivers. This is said to have helped the spread from humans to other humans.

Geography also helped understand the connections among colonialism, language, culture, and commerce that facilitated the movement of HIV. This is very involved and I cannot cover it in the space available in this column. The geography of HIV/AIDS is the topic of a three-hour workshop I conduct for students of classes 11 and above.

Now, another disease is in the news. Ebola. Ebola Virus Disease (EVD), or Ebola Hemorrhagic Fever (EHF), is caused by the Ebola virus. This is a deadly disease. Within 2–3 days of contracting the virus, symptoms start with fever, headache, and pain in the throat and muscles. This escalates to diarrhea, nausea, vomiting, and failure of liver and kidneys. It is usually fatal unless immediate care is taken. The diffusion is by contact with infected humans’ body fluids (therefore, contagious diffusion).

Again, we find that the origins are in the environment where the virus is present. This is mainly in the Central African Republic. Human consumption of certain kinds of meat is the main bridge across which the virus travels to the human body. You can find very informative maps related to the outbreak of Ebola at this site of the World Health Organization (WHO).

Recently, the media have been carrying many stories of Ebola outbreaks in Africa. This is still going on and massive efforts are on to control it. The images of people who work with this problem are eerie — they are dressed in protective clothing head to toe and look like space aliens. That is how dangerous this disease is.

In brief, understanding the geography of an epidemic is crucial to combating it. This is one part of medical geography. There are many epidemic and non-epidemic diseases. Medical geography helps us understand the geographical (or spatial) patterns and processes of these. In turn, that understanding helps provide care for those affected and to devise ways of containing the diseases, or even preventing them in the future! Medical geography is a burgeoning field of study within geography.

You should consider this field for a very rewarding, fulfilling, and challenging career.

Things you can do:

1. Looking at the maps on the WHO site, consider each map and observe what each map shows about Ebola: where cases are reported, where different kinds of species of animals are found, the species in which Ebola have been found, and national and natural boundaries.
2. From these, observe and note how points, lines, and areas are used to depict this particular topic (namely, Ebola) on these maps.
3. From newspaper reports of recent days, try to find out the locations of the latest Ebola outbreaks and where the people who got infected are from (not all of them are natives). What brought these people to that location in the first place?
4. Make a list of communicable diseases that can spread spatially (from place to place). Pick an example or two and figure out where they break out and how they spread. This exercise should be able to give you some idea of contagious diffusion and possibly cascade diffusion. Talk to a doctor for information.
5. If you want to do a project involving medical geography, contact me (geo@tiigs.org). I will be glad to help.

(A version of this article appeared in the Deccan Herald Student Edition on 31 July 2014.)