CHICAGO--(BUSINESS WIRE)--Fitch Ratings has placed Humana Inc.'s (HUM) ratings on Rating Watch Positive. The rating action follows HUM's July 3 announcement that it had entered into a definitive agreement under which it will be acquired by Aetna Inc. (AET) in exchange for cash and AET shares valued at $37 billion. Fitch rates HUM's senior unsecured notes 'BBB' and the Insurer Financial Strength (IFS) ratings of certain HUM insurance company subsidiaries 'A'. KEY RATING DRIVERS Fitch's decision