Payer

Salem Health (Ore.) and United Healthcare have renewed their contract, according to a Statesman Journal article.

Cigna has rejected Anthem's latest takeover bid, according to The New York Times.

Jacksonville, Fla.-based St. Vincent's HealthCare and Florida Blue have yet to reach a deal to keep St. Vincent's in the Florida Blue network, even thought their contract has nearly expired, according to The Florida Times-Union.

Recent merger frenzy talks involving five of the nation's largest health insurers have become a cause of concern for many in the healthcare industry.

Here are 125 things to know about Blue Cross Blue Shield, UnitedHealthcare, Aetna, Cigna and Humana — five leading health insurers in the U.S.

Aetna's roots go back to the 1850s, when Aetna Insurance Company organized an annuity fund to sell life insurance. Since then, Hartford, Conn.-based Aetna has become one of the nation's largest insurance companies, providing insurance to roughly 46 million people.

Activity is bubbling in the healthcare payer market, as rumors of acquisitions are surfacing. One of those payers, among the big five key companies, is UnitedHealthcare.

Bloomfield, Conn.-based Cigna was formed through the combination of INA Corporation and Connecticut General Corporation in 1982. The company has since evolved into one of the "big five" health insurers in the U.S.

UnitedHealth Group has approached Aetna about a takeover deal within the past few days, according toThe Wall Street Journal.

Shares of health insurer Cigna jumped nearly 12 percent Monday after it was reported that Anthem had made two takeover bids for Cigna within the past two weeks, according to a Hartford Courant report.