Don J. Scott Berin

Towards the end of Louis Pasteur’s life, he confessed that germs may not be the cause of disease after all, but may simply be another symptom of disease. He had come to realize that germs seem to lead to illness primarily when the person’s immune and defense system (what biologists call “host resistance”) is not strong enough to combat them. The “cause” of disease is not simply a bacteria but also the factors that compromise host resistance, including the person’s hereditary endowment, his nutritional state, the stresses in his life, and his psychological state. In describing one of his experiments with silkworms, Pasteur asserted that the microorganisms present in such large numbers in the intestinal tract of the sick worms were “more an effect than a cause of disease. With these far-reaching insights Pasteur conceived an ecological understanding of infectious disease. Infectious disease does not simply have a single cause but is the result of a complex web of interactions within and outside the individual.

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