Therefore it makes its victims less sick so that it can stay inside them longer and be transmitted more frequently. As-yet unpublished work from his lab has, Ewald says, provided the strongest evidence that simply cleaning up a water supply not only reduces human exposure to the cholera germ, but makes the germ less virulent. The evolutionary perspective shifts the way microorganisms and disease are conceptualized. Microbes are ubiquitous and ineradicable-it can even be said that humans inhabit the microbial web rather than vice versa. Human and microbial fates are inextricably intertwined.
Interspecies relationshipsoccupy a spectrum, from mutualism to parasitism.
If we can do anything to make sure that those organisms that are living inside us are very mild, we'll be better off. The perspective is very promising, but not all microbes may respond to evolutionary nudging. And the human immune system is as complicated as the microbial web. Just deciding whether an organism is harmful has become difficult. Thus one person's benign companion may be another person's fatal germ.