Clinical illness with laboratory confirmation of infection:
- isolation of Brucella sp. from an appropriate clinical specimen OR
- a significant (e.g. fourfold or greater) rise in Brucella agglutination titre between acute- and convalescent serum specimens obtained 2 or more weeks apart and tested at the same laboratory
- clinical illness in a person who is epidemiologically linked to a confirmed case OR
- clinical illness with supportive serology (Brucella agglutination titre of 160 or higher in one or more serum specimens obtained after onset of symptoms)
Clinical illness is characterized by acute or insidious onset of fever, night sweats, undue fatigue, anorexia, weight loss, headache, and arthralgia.