Europeans also brought diseases against which the Native Americans had no immunity. Chicken pox and measles, though common and rarely fatal among Europeans, often proved fatal to Native Americans, and more dangerous diseases such as smallpox were especially deadly to Native American populations. It is difficult to estimate the total percentage of the Native American population killed by these diseases. Epidemics often immediately followed European exploration, sometimes destroying entire villages. Some historians estimate that up to 80% of some Native populations may have died due to European diseases.