Aetna Inc.’s $34.1 billion deal to buy Humana Inc., announced early Friday, marks the first combination following weeks of deal talks among the largest health insurers as they race to bulk up in a market reshaped by the federal health-care overhaul.

Aetna will pay $230.11 a share for its smaller rival, 54% in cash and the rest in Aetna shares. The tie-up would create the No. 2 health-insurance company by revenue, pairing Humana’s strong Medicare franchise with Aetna’s core business of selling coverage to employers.

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