A bacterial illness characterized by fluctuating fever, caused by Brucella bacteria. In humans, the condition can result in general fatigue, weight loss, and anemia. While it is rarely passed from person to person, it commonly spreads from animals to humans, often through the consumption of unpasteurized milk from an infected animal. The main sources of infection are cattle, goats, and pigs. The disease is also known as brucellosis, Malta fever, Mediterranean fever, and undulant fever.