CVS Health, the giant drugstore chain that also runs walk-in clinics and a pharmacy benefit business, is in talks to buy Aetna, one of the nation’s largest health insurance companies, according to people briefed on the talks.

Negotiations between the two companies could still fall apart, these people say. But if consummated, the deal could be worth more than $60 billion based on Aetna’s current market value, which would make it one of the largest corporate acquisitions this year and one of the largest in the history of the health industry.

The proposed combination reflects the blurring of traditional boundaries in health care, as established companies seek to find their footing in a rapidly changing environment. Congress is deadlocked over the future of the Affordable Care Act, and employers and consumers are struggling to contain rising medical costs, particularly skyrocketing drug prices.

“I think this deal has been a long time coming,” said Adam J. Fein, president of Pembroke Consulting, a management advisory and business research company. “CVS has been positioning itself as a health care company and not a pharmacy for a long time.”