Legionnaires' disease imported to Denmark from Italy.

Three cases of imported Legionnaires' disease are reported. All 3 patients became ill after their return to Denmark from a holiday tour in northern Italy. High titers of antibodies to Legionella pneumophila in the indirect immunofluorescence (IF) test confirmed the diagnosis. The fact that the onset of illness was within 10 days of the last day the patients spent in Italy strongly suggests that the disease was imported to Denmark from Italy. 10 of the 77 tourists who participated in the study had IF titers of at least 256. Of these 6 had clinical signs of Legionnaires' disease. An additional case of legionella infection occurred months after the case described in this report and was probably contracted in Italy.