Perhaps sneezing is also a sharing mechanism, not because of vaccination effect, because of the cappacity to spread the disease in a not so virulent form. If the microorganism can infect the most quantity of hosts without a very agressive strategy it will be stable and not evolve to increase virulence. If killing hosts is what infects the most hosts it will be selected to do so. Maybe the body developed this sneeze reflex as a prophylactic measure. Facilitating the spread of non-lethal diseases and in doing so preventing them from being seduced by the lethal option which is a very juicy alternative.
I once saw a talk which described how when a country with cholera controlled the sewage in a way that corpse & dying patient contaminated water was prevented from reaching the public supply, forced the bacterium to be less virulent, keeping people alive more as the fittest way to survive. The strategy didn’t eradicate, but attenuated the disease. Better to have seasonal flu than SARS.
Seth: Good points.
