Map of the Week 11-28-2011:The Spread of Disease

There is perhaps no more natural use of the flow-type thematic map than to show the spread of disease.  This map, by Haisam Hussein, shows the origins and pathways of some of the most historically common and deadly of the world’s diseases, especially those with a global reach.  From: http://www.laphamsquarterly.org/visual/maps/contagion.php (go there to see detail of map)

Smallpox, leprospy, and malaria are or were all widespread health problems for millions of people, for millennia, and it is fascinating to see how these diseases diffused across the oceans and continents over time.  Now-a-days, of course, contagious diseases have a much more rapid and far-reaching diffusion, due to higher rates of international travel, increased travel between well-populated and remote areas, and the prevalence of air travel.  A new disease can get from one continent to another in a matter of hours, and diseases that were relatively local in extent can now spread throughout the world.   

We have probably all seen the maps of how the Black Plague was carried from Asia to Europe on ships, and major port cities were the ones that were affected first, in a kind of hierarchical diffusion.  Within weeks, however, the disease usually spread out from the port cities into increasingly smaller towns and villages, generally along trade routes overland, or secondary shipping routes to smaller ports.  

Trade ways in the 14th century

This is an abstract from a paper about the spread of the Plague in Sweden in the 14^th century, showing just that sort of diffusion. 

“GIS (Geographical Information Science) is used to describe and visualize the effects of the 'Black Death,' the worst pandemic in man’s history. The study is limited to models for the dissemination of the disease in Sweden in 1350. Simulations are made to depict different scenarios on the dissemination of the disease as well as the drastic changes in the overall population of Sweden over a couple of hundred years.

This work is based on the prevailing theory that the disease called the “Black Death” was plague (bubonic plague), caused by the bacterium Yersinia Pestis. The model assumes that the bubonic plague is caused by the bacteria Yersinia pestis through rat flea borne transmission to humans. For purpose of validation the population decrease estimated in each parish is compared with independent historical documents. Results from model scenarios are visualized in a series of maps and/or as animated video sequences. Generated map documents can be published as web map services.” From: A GIS BASED MODEL FOR DISSEMINATION OF THE BLACK DEATH IN SWEDEN IN 1350, Skog, Lars, Hauska, Hans, Broström, Anna.  Transactions in GIS.

  

Infected rats enter ports of Southern Sweden on 1st , 10th, 20th and 30th of June 1350. Therafter

the Black Death is spreading, parish by parish…

At the end of October 1350 the Black Death has spread all over Sweden, up to the latitude of Umeå

Of course, the bubonic plague is still with us, still affecting people, it is not an extinct disease, like smallpox.  This paper is about the current conditions in Africa pertaining to the spread of plague. 

Figure 1 - Geographic overview of plague in Africa

Overall figure: projection of the ecological niche model based on all 45 occurrence locations from Sub-Saharan Africa. Dark shades indicate areas with greater model agreement in predicting areas as suitable for plague. Occurrence points in sub-Saharan Africa on which predictions were based, are shown in light blue; independent test points in Madagascar and North Africa are shown in green.  Inset: 45 occurrence points, colored differently to indicate the four regional subsets: subset A (dark blue triangles); subset B (light blue squares); subset C (green circles); subset D (pink diamonds). Sub-Saharan region shown in inset covers training region used for ENM development.

From: Geographic distribution and ecological niche of plague in sub-Saharan Africa

International Journal of Health Geographics 2008, 7:54 doi:10.1186/1476-072X-7-54

Simon Neerinckx, A Townsend Peterson, Hubert Gulinck, Jozef Deckers,

Herwig Leirs

And here is something interesting from MIT's Senseable City Labs - HealthInfoScape - a way to visualize the connections between various medical conditions using 7.2 million electronic medical records of patients.
See the YouTube video at: http://www.youtube.com/watch?v=ln6arKcE99E&feature=channel_video_title
Here are the interactive maps: http://senseable.mit.edu/healthinfoscape/

Contagion Diffusion – The Euro Crisis

The euro zone’s single currency makes it easy to shift money across borders from risky economies to safer ones.  That and the lack of central banks in each country -- those went away in 1999 with the arrival of the euro — make the euro zone “the ultimate contagion machine,” says Kenneth Rogoff, a Harvard economist.

Arrows show imbalances of debt exposure between borrowers in one country and banks in another; arrows point from debtors to their bank creditors.  Arrow widths are proportional to the balance of money owed.  For example, French borrowers owe Italian banks $50.6 billion; Italian borrowers owe French banks $416.4 billion.  The difference — their imbalance — shows France's banking system more exposed to Italian debtors by about $365.8 billion.

The risk to countries’ debts and economies is indicated by color. 

The euro zone’s single currency makes it easy to shift money across borders from risky economies to safer ones.  That and the lack of central banks in each country – those went away in 1999 with the arrival of the euro – make the euro zone ‘the ultimate contagion machine,’ says Kenneth Rogoff, a Harvard economist. 

Arrows show imbalances of debt exposure between borrowers in one country and banks in another; arrows point from debtors to their bank creditors.  Arrow widths are proportional to the balance of money owed.  For example, French borrowers own Italian banks $50.6 billion; Italian borrowers owe French banks $416.4 billion.  The difference – their imbalance – shows France’s banking system more exposed to Italian debtors by about $365.8 billion.  The risk to countries’ debts and economies is indicated by color.  From: http://www.nytimes.com/interactive/2011/10/23/sunday-review/an-overview-of-the-euro-crisis.html?nl=todaysheadlines&emc=thab1

         Many of you undoubtedly remember the topic of geographic diffusion from Geography 101 or the equivalent class.  You know, the four major types of spatial diffusion: relocation diffusion, expansion diffusion, hierarchical diffusion, and contagion (or contiguous) diffusion.  The New York Times this morning published a very nice set of interactive graphics explaining the current situation with the Euro debt crisis, and how it’s all connected in one big old global web.  They use the term “contagion diffusion,” which strictly speaking from a spatial analysis perspective, is not an entirely correct use of the term.  However, if you have any confusion about the problem with the Euro and how Greek debt can influence events in the U.S. and worldwide, it is worthwhile to read the short text accompanying the graphics, and to poke around in the interactive graphics a bit.  And I think the term "contagion diffusion" is a more-or-less apt description to get the main point across, although in this case the contagion or contiguity is not referring to geographic contiguity but to monetary contiguity, since the countries influencing one another are not necessarily geographically contiguous, but are connected via this non-spatial network of money. Maybe, to coin a new term, it could be called "network diffusion" since the diffusion is occurring via the international monetary network, as opposed to any of the other typical types of diffusion. If anyone has a better name for it, please let me know!   In any event, the Times showcases here some good examples of conceptual flow maps, and as usual, the Times graphics are excellent.  I am slightly envious of the high school kids in our GISc Science Academy this summer who got to take a field trip to the New York Times graphics dept. 

      Check out the six different conceptual flow diagrams which give an overview of the crisis at:  http://www.nytimes.com/interactive/2011/10/23/sunday-review/an-overview-of-the-euro-crisis.html?nl=todaysheadlines&emc=thab1

      For NY Times print version, see: http://www.nytimes.com/imagepages/2011/10/22/opinion/20111023_DATAPOINTS.html?ref=sunday-review

The Four Major types of Spatial Diffusion.  From: http://www.spatial.maine.edu/~max/KEH_i21.html

The euro zone’s single currency makes it easy to shift money across borders from risky economies to safer ones.  That and the lack of central banks in each country -- those went away in 1999 with the arrival of the euro — make the euro zone “the ultimate contagion machine,” says Kenneth Rogoff, a Harvard economist.

Arrows show imbalances of debt exposure between borrowers in one country and banks in another; arrows point from debtors to their bank creditors.  Arrow widths are proportional to the balance of money owed.  For example, French borrowers owe Italian banks $50.6 billion; Italian borrowers owe French banks $416.4 billion.  The difference — their imbalance — shows France's banking system more exposed to Italian debtors by about $365.8 billion.

The risk to countries’ debts and economies is indicated by color. 

The euro zone’s single currency makes it easy to shift money across borders from risky economies to safer ones.  That and the lack of central banks in each country -- those went away in 1999 with the arrival of the euro — make the euro zone “the ultimate contagion machine,” says Kenneth Rogoff, a Harvard economist.

Arrows show imbalances of debt exposure between borrowers in one country and banks in another; arrows point from debtors to their bank creditors.  Arrow widths are proportional to the balance of money owed.  For example, French borrowers owe Italian banks $50.6 billion; Italian borrowers owe French banks $416.4 billion.  The difference — their imbalance — shows France's banking system more exposed to Italian debtors by about $365.8 billion.

The risk to countries’ debts and economies is indicated by color.