Download Nov 21, 2011 Infectious Diseases

The Biogeography of Infectious
Diseases
One of the consequences of the domestication of plants and animals and the
resultant increase in human populations was the increased importance of
infectious diseases. There were two basic reasons for this: 1) the increased
density of human populations, and 2) the transmission of infectious diseases to
people from their domesticated animals (See Jared Diamond’s “Guns. Germs
and Steel” for a discussion of this theme). Below is his listing of “Deadly Gifts
from our Animal Friends.”
Measles
Tuberculosis
Smallpox
Flu
Pertussis
Falciparum malaria
Cattle
Cattle
Cattle
Pigs and Ducks
Pigs and Dogs
Birds (Chickens and Ducks)
How do infectious diseases spread through a population?
The spread of an infectious disease though a population
can be thought of as a wave like phenomenon. The graphs
on the next two pages show how this works. Note that the
term “epidemic” in medical geography means “always present in
the population.”
Two Examples of Infectious Disease
• The Plague
• Influenza
The Plague
This disease involves interactions between several species.
The Vector: Xenopsylla cheopsis
The Agent: Yersinia pestis a bacterium
The Host: Rattus rattus – the Black Rat
There have been three major outbreaks (pandemics)
during the last 2,000 years.
The population of Western Europe
PATTERSON, K. DAVID, The Geography and
Mortality of the 1918 Influenza Pandemic ,
Bulletin of the History of Medicine, 65:1
(1991:Spring) pp.4-21
25-40 million people died
My grandmother died of the flu in 1918.
For a model that shows the spread of a flu epidemic throughout the US
click here and start the movie:
http://www.nigms.nih.gov/News/Results/Flu
Model040306.htm
For a general summary of what the model does click here:
http://publications.nigms.nih.gov/Multimedi
a/Video/vaccine-19.html
The details behind the model are published in the following (very technical)
journal article. For a copy click here:
http://www.pnas.org cgi doi 10.1073 pnas
.0601266103
Germann et al. PNAS April 11, 2006 vol. 103 no. 15 5937