Intercontinental travel and its effect on pre-existing illnesses.

Over 12,000 European air passengers were interviewed as to whether the status of any pre-existing illness changed as a result of their vacation in the tropics or in North America (United States or Canada). Of the travelers to tropical destinations, 1.6% reported their disease had improved, which significantly exceeded the rate of 0.5% in visitors to North America, mainly due to a more favourable influence in chronic respiratory tract infections and chronic rheumatologic impairment. Aggravation of pre-existing disease occurred in 0.9 and 0.7%, respectively, of the travelers in the two groups and was only rarely severe. In the tropics, patients below the age of 30 and those who suffered from digestive problems were most frequently adversely affected.