>Ewald showed that infectious agents that used intermediate vectors for transmission, such as malaria's mosquitoes and cholera's contaminated water, are free to evolve towards greater destructive power. >The theory predicts that a disease like Varroa, that spreads easily among colonies, will evolve towards being more benign to bees, while AFB, that can lay dormant in the environment, being vectored by next cavities, will tend to be more virulent. So, what does this mean for the virus diseases that are showing up in honey bees that are believed to be vectored by varroa? Regards, Dick