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NEW YORK, Aug 24 (Reuters) - Ohio's Department of Insurance said on Thursday that non-profit managed care company CareSource will sell health plans in Paulding County next year - the last county in the United States that would have been without Obamacare individual coverage in 2018.

The Centers for Medicare and Medicaid Services (CMS) said on Wednesday that only Paulding County in northwestern Ohio was projected to be a "bare county" with no insurers in 2018, while 1,478 counties could have only one issuer next year.

Just a month ago, CMS said there were 40 counties projected to have no insurers next year.

Health insurers are facing an upheaval in their businesses amid growing uncertainty about healthcare legislation under President Donald Trump, who seeks to follow through on his promise to dismantle former President Barack Obama's signature healthcare law, formally known as the Affordable Care Act.

Insurers such as UnitedHealth Group Inc, Aetna Inc and Humana Inc have exited most of the states where they sold Obamacare plans, leaving hundreds of U.S. counties at risk of losing access to private health coverage in 2018.

But other insurers, like Centene Corp, have filled those gaps, expanding into new counties that had lost their coverage options.

In June, Centene said it would enter into three new states and would expand operations in six existing markets in 2018. (Reporting by Michael Erman, editing by G Crosse and Tom Brown)