One possible cause of their vulnerability is that the virus has evolved around its problem, and found away to usea slightly different chemokine receptor as away into its target macrophages.
If the respective major tours were to go their own way it could lead to a situation where players could usedifferent putters in events on either side of the Atlantic.
They seem to have figured out away to produce an unlimited supply of clones efficiently-- which means they either usea completely different method to create those clones, or they have an unlimited supply of human egg cells.