Uncontacted people, also referred to as isolated people or lost tribes, are communities who live, or have lived, either by choice (peoples living in voluntary isolation) or by circumstance, without significant contact with global civilization. Few peoples have remained totally uncontacted by global civilization. Indigenous rights activists call for such groups to be left alone, stating that it will interfere with their right to self-determination. Most uncontacted communities are located in densely forested areas in South America, New Guinea, India, and Central Africa. Knowledge of the existence of these groups comes mostly from infrequent and sometimes violent encounters with neighboring tribes, and from aerial footage. Isolated tribes may lack  immunity to common diseases, which can kill a large percentage of their people after contact.