Board Thread:Metal Gear Solid V/@comment-42.2.187.80-20150911172559/@comment-6747658-20151001140537

Uhm, it was never explicitly stated that Zero was infected with the English strain, only that he was infected by parasites which most likely were not even the Vocal Cord one else Zero would be dead rather then comatose, not to mention he would have infected everyone else he had gotten in touch with, Big Boss included when Zero went to visit him. So practically everything you've said is nothing more then an assumption, where as the game pretty heavily hints and implies that Quiet has the English strain.