As the English, French, and Spanish explorers came to North America, they brought tremendous changes to American Indian tribes. Europeans carried a hidden enemy to the Indians: new diseases. Native peoples of America had no immunity to the diseases that European explorers and colonists brought with them. Diseases such as smallpox, influenza, measles, and even chicken pox proved deadly to American Indians. Europeans were used to these diseases, but Indian people had no resistance to them. Sometimes the illnesses spread through direct contact with colonists. Other times, they were transmitted as Indians traded with one another. The result of this contact with European germs was horrible. Sometimes whole villages perished in a short time.