Environmental Engineering Reference
In-Depth Information
tion contact and conflict, there have been several distinct transitions in the
relationships of
with the natural world (McMichael 2001a).
Each of these transitions in human ecology and in inter-population interac-
tion has profoundly changed the patterns of infectious disease.
The three great historical transitions since the early emergence of agri-
culture and livestock herding from around 10 000 years ago occurred when:
Homo sapiens
i
early human agrarian-based settlements enabled various species of
animal-infecting microbes (usually as mutant strains) to enter
Homo
sapiens
, thereby creating new human diseases such as smallpox,
measles, typhoid, tuberculosis, leprosy, the common cold, influenza,
and dozens of others;
ii
early Eurasian civilisations (such as the Roman Empire, China and
South Asia) came into military and commercial contact, around 2000
years ago, swapping their dominant infections; and
iii
European expansionism, over the past five centuries, caused the
transoceanic spread of oft-lethal infectious diseases.
This latter transition is best known in relation to the conquest of the
Americas by Spanish conquistadors, when the inadvertent spread of measles,
smallpox and influenza decimated the vast native Amerindian populations
of Central and South America. Similarly, the introduction of smallpox (and
other infectious diseases) to Australian Aboriginals soon after European set-
tlement caused local devastation of many Indigenous communities.
Today, we may be living through a fourth great transitional period. The
contemporary spread and increased adaptability of various infectious dis-
eases, new and old, reflects the impacts of demographic, environmental,
behavioural, technological and other rapid changes in human ecology.
Within the realm of clinical medicine, there are various manoeuvres that we
now routinely use that have provided very inviting opportunities for oppor-
tunistic microbes. These include blood transfusion, organ transplantation
and the widespread use of hypodermic syringes. These have contributed to
the rising iatrogenic (caused by medical examination or treatment) prob-
lems of hepatitis C, HIV/AIDS, and several other viral infections. The
increasing problem transmission of hepatitis C via blood transfusion in Aus-
tralia, identified during the 1990s, has necessitated new procedures for
screening blood donation.
