Leprosy's decline caused by rise of TB

But not how you would think. Leprosy takes long-term intimate contact to spread. Since the two pathogens are similar leprosy sufferers in the Middle Ages were predisposed to catch TB. As people crowded into cities and TB became prevalent, the lepers were the first to catch it and die from it. TB selectively thinned the ranks of the lepers to the point that leprosy just became a rarer disease. This counters the earlier assumption that TB somehow transmitted an immunity to leprosy.