The presence of large groups of people in close proximity proved a fertile breeding ground for all manner of epidemic and endemic diseases throughout the early modern period. Water supplies were often contaminated as people empted their waste into the nearest available stream or river. Plague was certainly present during the sixteenth and early seventeenth centuries in Welsh towns, although it appears to have made less impact here than in some parts of England. Smallpox too was an endemic disease which often became epidemic, and was certainly notorious throughout Wales during this period, killing around a quarter of those who contracted it. Urban areas tended to follow different patterns of mortality to those in the countryside. Diet was another strong factor affecting susceptibility to disease. Malnutrition lowered immunity to disease, especially during harvest failures and poor weather when staple crops were in short supply.