What if there’s no affordable insurance to buy?

Leslie Kurtz needed three plates, eight screws and a big assist from her insurer after breaking every bone in her ankle while white water rafting.

Coverage she purchased through a public insurance exchange established by the federal health care law paid $65,000 toward surgery and the care she needed after the 2015 accident. But that protection may not exist next year because insurers have abandoned the Knoxville, Tenn., resident’s exchange. As of now, Kurtz has no future coverage options, and she is worried.

“I can’t afford to have everything I’ve worked for taken away because I fell down the steps,” Kurtz said.

Her county is one of 16 in Tennessee that lack even a single insurance company committed to offering coverage for 2018 on the exchange, after Humana announced last month plans to exit.

Exchanges set up by the Affordable Care Act were designed to give customers a chance to shop for coverage and then buy a plan, most with help from tax credits. The idea was that such a marketplace would push insurers to offer affordable plans to compete for customers.

But insurers in many markets have been pulling back from the exchanges after losing money. According to an analysis by the Associated Press and the health care firm Avalere Health, more than 1,000 counties, where about 2.8 million people are insured through the exchanges, are down to their last insurance carrier, according to the most recent data.

With less competition, that could mean sharply higher rates. And with more insurers still considering leaving other markets, customers around the country could be stuck like Kurtz with no affordable coverage options in 2018.

Insurers still have a few more weeks to decide to stay in their exchanges, and other insurers may jump into new markets, though that can be expensive and risky for them. The government recently announced several short-term fixes for the exchanges, and insurers have welcomed the moves. But they want to see the final version of the improvements before deciding on 2018.

“No insurer wants the negative public backlash from dropping insurance for lots of people, but the companies need to feel like the market is stable and that there’s a chance of making money,” said Larry Levitt, a health insurance expert with the nonprofit Kaiser Family Foundation.

Chief among undecided companies is the BlueCross-Blue-Shield carrier Anthem Inc. It is the lone insurer on exchanges in 300 counties in seven states, according to data compiled by the AP and Avalere.