emerging diseases

anonymous anonymous.scripps.edu
Wed Oct 25 23:07:36 EST 1995


   The hypothesis you are exploring is a good one, and I believe that
there are probably many instances of disease being initiated by human
actions.  You may find some interesting information in books such as "The
Coming Plague" or "New Guinea Tapeworms and Jewish Grandmothers" (The
latter of these...I'm not 100% sure about the title...is a terrific and
easy to read account of how some outbreaks have been caused by alterations
in human lifestyles, including environmental changes).  
   I think it would also be useful to comment upon some of the ways in
which improved sanitation measures have actually altered the face of a
disease. A terrific example of this is polio, which was caused a
relatively benign infection when it struck very young infants. The reason
for the benign infection was that they enjoyed a passive immunity
conferred from the mother.  Increasing effectiveness in sanitary measures
reduced the frequency of the poliovirus to the extent that children were
often infected slightly later in life, when they no longer possessed the
passive immunity of their mothers.  In this situation, the virus causes
much more serious infections, including poliomyelitis.  (See Fields
'Virology' for an interesting account of poliovirus epidemiology).
   While there are without question some interesting accounts of cases in
which alterations in lifestyle (including environmental changes) have
allowed a previously 'benign' virus to exploit a new niche, often with
dire consequences. Nevertheless, I think it would be unfair to focus
specifically on the negative aspects of human interventions...many
diseases have been brought under control (for now) which previously
wreaked havoc upon societies (i.e. smallpox, polio (through the Salk
vaccine & others, TB...for now, etc.)  I think one of the most interesting
hypotheses regarding 'emerging viruses' is that they are not 'new' at all,
but rather exploiting a presented niche when normal patterns are
disrupted.  The hantavirus outbreak, for instance, was caused b/c of a
mouse (the natural host) explosion following a bumper crop year.  This
brought the mice closer to humans, which they subsequently infected. 
While it is still possible to blame this outbreak on human actions (say,
agriculture and foodstocking), I think it is more reasonable to say that a
natural balance was disrupted which led to abnormal conditions for the
spread of a disease.

Anyway, I would recommend the two texts I mentioned above for a further
look into this question, which is undoubtedly a very interesting one.  I
must put in a plug for Field's Virology though...if you are truly
interested in learning about disease epidemiology, there is no substitute
for good scientific knowledge regarding the diseases in question. Many
popular texts (The Coming Plague in particular) come up short in
scientific detail.

John C. Tilton
The Scripps Research Institute

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