Syphilis

Unwashed savages!

Funny enough, Europeans of the 15th and 16th centuries were more likely to be unwashed than their medieval predecessors. Bath-houses had acquired something of a seedy reputation, a medical fad that suggested bathing was unhealthy was in vogue, and it was seen as a mark of humility (very Christian and virtuous!) to go long periods without such vanity as washing oneself. In the medieval period, at least, you’d have even rural people rinsing in the river on the regular!