Walmart is in talks with health insurer Humana for a closer partnership to provide health care to consumers at home and prevent illness, according to a person familiar with the matter.

Health-care spending accounted for about 18 percent of the U.S. economy last year, and continues to surge with an aging population, pricey medications, and a complex regime of reimbursements and middlemen. Companies have been trying to address some of the market’s inefficiencies by forging alliances or getting bigger: Cigna Corp. is acquiring Express Scripts Holding Co. for $54 billion, and CVS Health Corp. is buying Aetna Inc. for $68 billion.

Walmart and Humana have explored a wide range of options including a merger, though an outright combination isn’t likely at this point, said the person, who asked not to be identified discussing private information. The Wall Street Journal reported Friday that Walmart was in early talks to acquire Humana.