Privileged classes of people and sometimes common people with difficult medical problems have always traveled to undergo treatment outside their home country. Nineteenth-century centers of medicine in Europe attracted patients from colonies in Africa and the Far and Middle East. In the 20th century, the growing fame and prestige of specialized centers such as the Mayo Clinic, Cleveland Clinic and Johns Hopkins attracted large numbers of patients to the United States. The numbers grew along with the expansion of air travel and the development of new technologies and procedures, such as bypass surgery, which were unavailable elsewhere.
Hospitals and Health Network Magazine, By David Ellis, 1/17/2012