>
> >The cause for polio was unknown then.


That observation brings up a thought re beekeeping:
"Before the 20th century, polio infections were rarely seen in infants
before six months of age, most cases occurring in children six months to
four years of age. Poorer sanitation of the time resulted in a constant
exposure to the virus, which enhanced a natural immunity within the
population. In developed countries during the late 19th and early 20th
centuries, improvements were made in community sanitation, including
better sewagedisposal and clean water supplies. These changes drastically
increased the proportion of children and adults at risk of paralytic polio
infection, by reducing childhood exposure and immunity to the disease."
 Wikipedia.

My point is that species co-evolve with their parasites (polio virus being
a parasite).  When we mess with the "equilibrium," we can upset the
"balance"--in the case of polio, the unintended consequence of better water
sanitation in the US was the likely cause of the 1952 polio epidemic.

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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