Rocky mountain spotted fever caused by blood transfusion.

Transfusion of 500 ml of blood, contributed by a donor three days before the onset of Rocky Mountain spotted fever and refrigerated for nine days, caused this disease in the recipient. The blood donor died of Rocky Mountain spotted fever after six days; rickettsia were identified in various tissues by immunofluorescence techniques. The recipient of the blood became mildly ill and recovered fully; specific antibiotic treatment was initiated on the fourth day of illness. Diagnosis of Rocky Mountain spotted fever was confirmed in the recipient by positive serologic reactions and isolation of Rickettsia rickettsii from blood after inoculation in animals and tissue culture.