When population transfer occurs, it inevitably creates health concerns. A historical example is the removal of Native American Indians from their homelands in the southeastern states to reservations west of the Mississippi beginning in 1831. The forced marched resulted in exposure to harsh weather conditions, starvation and disease. Approximately 4,000 Cherokees died during the march that became known as the Trail of Tears. Wars cause direct and indirect population transfers as seen in the current mass exodus from Syria, many on overcrowded rafts and boats. Millions have fled and over 80,000 Syrians live in the Zaatari refugee camp in Jordan. The World Health Organization (WHO) and other aid organizations provide health care, education, food, security and social services. Nearly 75 percent of the visits to clinics within the refugee camp are due to communicable diseases. In addition, one of the most needed services is mental health counseling, which is often in short supply. Children comprise approximately half of the population and need immunizations and proper nourishment. Teams of volunteer health professionals from around the world provide medical care for the refugees. In 2016, a team of 80 volunteers from a Catholic community hospital in Chicago provided cardiac, eye and orthopedic surgeries and care in pediatrics, obstetrics, dentistry, pain management and nephrology. Doctors Without Borders is one of many organizations that provide medical care for Syrian refugees in Jordan, Iraq, and Lebanon. These medical teams are comprised of physicians, nurses, and medical staff that often work in dangerous conditions.