As I understand BD (and I think I do) it is in
no way contagious from one coin to the next. Coins which were buried in acidic,oxygen-free soil may develop an unstable layer under the
patina, When dug up, they are exposed to oxygen and moisture which reacts with this unstable material to destroy the
patina.
BD cannot transmit from coin to coin but the spread of this rot across the surface ( though the source of the problem is beneath) gives one the idea of a "disease". It cannot be cured but it can be stopped. The bad reaction requires moisture so, as Joe mentions, drying out your coins after you have cleaned them and keeping them dry is the best prevention.
Regards, Dave