The French have solved this problem.
You are speaking of the hypovirulent strain that attacks but doesnot kill the European Chestnut. It is a natural condition.
It does not spread naturally in America however. Individual trees can be innoculated with the hypovirulent fugus and will survive, but it doesn’t happen naturally in large populations.
I have actually done the procedure and it was successful in about 3 out of 5 All American Chestnut trees in the groves I tend to.