Under the Health Insurance Portability and Accountability Act (HIPAA), an agency or authority of the United States: a state; a territory; a political subdivision of a state, a territory, or an Indian tribe; or a person or entity acting under a grant of authority from or contract with such public agency including the employees or agents of such public agency or its contractors, persons, or entities to whom it has granted authority that is responsible for public health matters as part of its official mandate.