Brucellosis, also known as undulant fever or Mediterranean fever, is caused by the bacterium Brucella.
Brucellosis is a zoonosis (an infection acquired from animals). The most commonly affected animals are sheep and goats (with Brucella melitensis), cattle (with Brucella abortus), and pigs (with Brucella suis).
Brucellosis has been virtually eliminated from most developed countries, but it is still endemic in Africa, the Middle East, central and south-east Asia, south America and in some Mediterranean countries.
Humans can become infected by ingestion of unpasteurised milk or milk products, or via direct or indirect contact with infected animals.