Most fungi that grows on dead or rotting trees won't present a hazard to healthy living trees nearby. There are various mechanisms for a tree to become the target of a fungal infection, including poor pruning practices, mechanical damage, age, and, quite frankly, death of the tree due to other reasons.  The fungal organisms that are responsible are always around.  If your other trees are healthy, pruned correctly, and are protected from mechanical damage and winter damage, they should remain healthy. Here is a good discussion (it is from California, put the principles apply):
http://ipm.ucanr.edu/PMG/PESTNOTES/pn74109.html

Thank you, the article was very informative but it seems as though this is part of nature. I have an arborist come annually to look at my trees and prune what seems to be necessary but still it’s an issue. I live next to woods with many dead trees and it’s impossible to remove them. I’ll keep trying to keep my own trees healthy.