Chicago’s top federal prosecutor has established a new unit in his office to battle health-care fraud.Acting U.S. Attorney Joel R. Levin said Tuesday the unit will “bring even greater focus, efficiency and impact to our efforts in this important area.”The unit will prosecute defendants accused of offenses that include submitting fraudulent bills, falsifying diagnoses to justify expensive tests and performing procedures that are not medically necessary.“Every year, health care fraud causes millions …