I recall way back in college i think 1999 or 2000 I've read a book for a history class something called guns, steel and bugs or sometihing along those lines. It basically stated the difference in success of European settlers between attempting to settle in North America and thus using diseases like yellow fever etc etc to aid in expenasion (native Americans had very bad immunity against European strains) vs pilgrims going to holly land and having them asses handed to them because the disease profiles between Europe and middleeast we're similar but middleeast also has zoonotic diseases like malaria and dengue.