More than 70,000 Virginians are facing the prospect of having no insurer that will offer them Obamacare coverage for next year.

The news surfaced after roughly two weeks had passed after it was determined that every U.S. county in the country had at least one health insurer selling Obamacare plans. Insurer Optima Health, which said in August that it would offer coverage in every nearly county in Virginia, reversed its decision on Thursday.

The company announced that rather than expand it instead would reduce participation from the 35 counties it offered plans in this year. Optima will keep the Hampton Roads and Harrisonburg markets and enter the Charlottesville area, Halifax County, and Mecklenburg County. The move leaves 63 Virginia "bare" counties.

"The decisions we made were challenging ones given the recent changes and ambiguities in the marketplace," Michael Dudley, Optima president and CEO, said in a statement. "Our most recent filing with the state reflects these dynamic changes, as would be expected in these circumstances."

Optima is offering plans only in counties where its healthcare company, Sentara Healthcare, has doctors and hospitals doing business, and said it will allow the company to "better manage chronic conditions to keep members healthy."

Many of the empty counties are in rural areas, with low population density and few healthcare providers with which insurers can negotiate prices. Other insurers, including Anthem, UnitedHealthcare and Aetna announced their exit from Virginia earlier this year, citing losses and too much uncertainty ahead on how the Trump administration and Congress would handle Obamacare.

It's unclear whether the number of empty counties will continue to grow. Insurer Anthem, part of Blue Cross Blue Shield, announced Wednesday that it would scale back its Obamacare exchange participation in Kentucky.

Insurers have raised questions about whether they will receive payment for cost-sharing reduction subsidies under the law, which allow them to lower out-of-pocket costs for low-income customers. The funds became mired in a legal battle with the House and the Obama administration, and now the Trump administration is paying them out each month with no guarantee for the future.

The Senate is in discussions about appropriating the funds, which insurers say they need to be guaranteed in order to set their premium prices.

Insurers have until Sept. 20 to file rate requests and a week later to sign contracts with states, though the Trump administration can move the deadline.