Friday, April 22, 2011

Infection: the uninvited universe

Infection: The Uninvited Universe by Gerald N. Callahan is about the human ecosystem.  I don't mean the ecosystem humans inhabit.  I mean the ecosystem that is the human body. 

The human body contains more microbial cells than it does human cells.  A wide variety of bacteria call us home.  The usual inhabitants of the human ecosystem are benign or even helpful.  Callahan describes the important role they play in our everyday lives, and their necessity to the immune system and other bodily functions.

I find myself thinking about a question I've been pondering for some time.  Since the human body is an ecosystem, what is the impact of removing one species?  As we vaccinate for more and more diseases, are we potentially opening the door for bigger issues?

Chicken pox comes to mind.  This is a disease that has co-evolved with humans.  At this point in human history, it is mostly benign.  Very few people suffer any long-lasting or serious effects from the disease.  For most humans, it is merely a rite of passage.  But now it is a mandatory vaccination for school-age children. 

If we eradicate chicken pox from the human ecosystem are we opening that niche for a new species to move into?  Is it possible that removing chicken pox is going to free up room for a new disease-causing microbe to move in?  If so, the risk of a new microbe being deadly instead of benign is great.  Our first encounters with microbes tend to go in the microbes favor.  It takes time for us to get used to each other and learn to co-exist. 

Perhaps we should choose our battles wisely.

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