When people move from one city or country to another, the spread of disease may result. People often bring in germ that may not have been present there before. These new germs can spread quickly and cause previously unknown diseases. If a germ is completely new to a region, people who already live there have no natural protection against it. As result, they become ill more easily and died often. Sometimes, newcomers can catch disease that were not present where they come from. If they go back, they may carry the disease with them and bring about an epidemic there too.