Brucellosis (Undulant Fever; Malta Fever; Mediterranean Fever; Gibraltar Fever) By Larry M Bush, MD, FACP, Charles E Schmidt College of Medicine, Florida Atlantic University; Maria T Vazquez-Pertejo, MD, FACP, Wellington Regional Medical Center Reviewed / Revised Apr 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Prevention Key Points More Information Brucellosis is caused by Brucella species, which are gram-negative bacteria.