Parts of the country are in jeopardy of not having an insurer offering Obamacare plans next year.

Many counties already have just one insurer offering health plans in the Obamacare marketplaces, and some of those solo insurers are showing signs that they are eyeing the exits.

Humana announced this year that they’d be leaving the markets altogether next year. That means there are parts of Tennessee that will have no insurance options unless another insurer decides to enter.

And Anthem, which operates in 14 states, is getting nervous, an industry analyst told Bloomberg News this week. Its departure would be a much bigger problem. According to an analysis of government data by Katherine Hempstead at the Robert Wood Johnson Foundation, Anthem is currently the only insurance carrier in nearly 300 counties, serving about a quarter of a million people.

As you can see on our map of those counties, an Anthem departure could leave coverage gaps in substantial parts of Georgia, Missouri, Kentucky, Ohio and Colorado, as well as smaller holes in other states. In places where no insurance company offers plans, there will be no way for Obamacare customers to use subsidies to buy health plans.