The trend to merge health insurance companies into fewer unique entities continues apace as Anthem Inc. made a bid to buy rival health care insurer Cigna Corporation.

The latest bid for Cigna came after months of negotiations between the parties and a previous offer ten days ago. The latest takeover bid came when Anthem offered to buy Cigna for about $175 per share. Cigna is still saying no to the offers.

Health care giant Humana Inc. has also entered the fray, discussing a possible takeover of Cigna as well as Aetna Inc.

On Monday morning Anthem’s market value was estimated at $43 billion, and Cigna’s was approximately $35 billion.

Cigna stock soared in the wake of the Wall Street Journal story about the takeover bid, climbing 12 percent in active midday trading, reaching $153.74 per share. Anthem shares also grew, adding 2 percent to close at $164.22.