Page 202 - Berkshire Encyclopedia Of World History Vol Two

diseases, animal 551

Cunningham,A., & Williams, P. (1992). The laboratory revolution in med- spread through populations previously unexposed to
icine. Cambridge, UK: Cambridge University Press. epidemics, typically causing 90–95 percent mortality.
Ewald, P. W. (1994). The evolution of infectious disease. New York:
Oxford University Press. Overall, these diseases may have killed as many as 100
Grmek, M. (1989). Diseases in the ancient Greek world (L. Muellner & million people in the Americas.
M. Muellner,Trans.). Baltimore: Johns Hopkins University Press.
Kiple, K. (1993). The Cambridge world history of human disease. Cam- Prominent examples of infectious diseases that have
bridge, UK: Cambridge University Press. crossed from other animals into humans include small-
McNeill,W. H. (1998). Plagues and peoples (2nd ed). New York: Anchor pox, cholera, tuberculosis, bubonic plague, and influenza.
Books.
Although AIDS represents a major potential health prob-
lem in the modern world, it is contagious, but neither
infectious nor acute. In recent years there have been pan-
ics over other animal diseases such as hoof and mouth
Diseases, Animal disease, Hanta virus, and so-called mad-cow disease,
which may not be a disease in the usual sense at all.These
very disease that has caused epidemics and changed pathological conditions are trivial compared with the
Ethe philosophical traditions of societies throughout impact of the other diseases listed, yet they have received
human history has originated in nonhuman animals and more publicity, perhaps because of media-inspired fear
“jumped the species barrier” into humans. There is no and ignorance, combined with the fact that most people
meaningful separation between animal and human dis- do not understand how various diseases are transmitted.
eases when discussing the impact of disease on human Most infectious animal diseases that jump to humans
history. are caused by bacteria and viruses whose small size ren-
It is important to emphasize that because humans are ders them highly volatile and transmissible as aerosols,
mammals, diseases found in other nonhuman animals, hence more likely to be transmitted from one individual
especially other mammals, often cross readily into to another, which is the basis of contagion. A few dis-
humans.The most important diseases are infectious and eases, such as malaria and sleeping sickness, are caused
highly contagious. Noncontagious diseases have had lit- by protistans, single-celled eukaryotic organisms that are
tle or no impact on history. By definition, infectious dis- much larger than bacteria or viruses. The larger size of
eases are capable of being spread rapidly from infected to protistans means they cannot be transmitted as aerosols
healthy individuals. Infected individuals either die or and hence are transmitted primarily by injection, for
recover fully within a short period of time; those indi- example, through insect bites, rendering them much less
viduals who recover typically acquire immunity against infectious.
further infection by the same illness. Most infectious disease organisms co-evolve in inter-
The numerically greatest single documented epidemic actions with other nonhuman species.These nonhuman
in human history was an influenza outbreak that killed an species have evolved an immune response to the disease-
estimated 40 million people at the end of World War I. causing organisms, so they are not serious threats either
The epidemic having the greatest recorded impact was to health or population numbers in their original host
the bubonic plague that killed over 25 percent of the peo- species.What renders most of infectious diseases so viru-
ple in western Europe in the mid-fourteenth century. lent in human populations is that when first exposed, hu-
Despite a lack of documentation, however, the epidemics mans have no evolved immune response to these patho-
with the greatest overall impact both on human popula- gens; for example, smallpox is related to bovine pox,
tions and history were the series of epidemics that spread which causes minor problems in cattle but is often fatal in
through the Americas shortly after contact with Euro- its mutated form in humans. Similarly, the AIDS virus is
peans and their domestic animals. These epidemics closely related to a viral infection that occurs in African