The 5,242 New London County residents who currently have health insurance coverage through Access Health CT, the state’s online marketplace, are facing double-digit premium increases and may be forced to switch to a new company for 2017.

James Wadleigh, chief executive officer for Access Health CT, said Wednesday that there will only be two private insurance carriers offering coverage through the exchange in 2017, Anthem Blue Cross and Blue Shield and ConnectiCare. Each will be offering several plans.

The two companies remain after the departure of two other carriers on the exchange. HealthyCT’s insurance co-op, closed earlier this year, and UnitedHealthcare announced plans to leave the exchange at the end of this year.

Last week, ConnectiCare also announced plans to leave the exchange, but on Tuesday announced that it had reversed its decision. ConnectiCare insures about 48,000 people statewide on the exchange, but Anthem insures the majority of New London County residents enrolled through Access Health CT.

Premium costs for both remaining carriers will increase, Wadleigh said, with ConnectiCare rates rising an average of 17 percent and Anthem rates slated to rise a little more than 20 percent.

Yolanda Bowes, director of community outreach for United Community & Family Services in Norwich, said the rate hikes will be difficult for the 190 UCFS patients who have coverage through the exchange.

“It’s definitely going to be a challenge for them” she said. “It’s already a challenge for those clients.”

Statewide, Wadleigh said, about 100,000 have health insurance through the exchange, the majority of whom receive a federal subsidy to offset the cost of coverage.

Of the 5,242 New London County residents enrolled, 4,420 are covered by Anthem, which offered lower rates than ConnectiCare. Another 721 have ConnectiCare insurance. The remaining 101 who had been covered by either UnitedHealthcare or HealthyCT will have to choose one of the two remaining carriers when the open enrollment period for the new year begins on Nov. 1.

Bowes said she and other insurance counselors at UCFS are also working with patients who recently lost HUSKY A coverage provided by the state when income caps were raised on July 31.

Wadleigh said the number of people covered through Access Health CT has declined over the last two years, from a high of 116,000. At the same time, the number of uninsured residents has declined from 6.9 percent last year to 6 percent this year. The exchange was created in 2013 as the state’s response to the federal Affordable Care Act.

“It’s not necessarily a bad thing when people are leaving Access Health CT,” Wadleigh said. “They may be aging into Medicare, or they may have gotten a new job with employer coverage, or they’ve moved out of state.”

While the choices for 2017 will be more limited than ever before, Wadleigh said the exchange is working to improve the selection for 2018.

“We are aggressively looking at that,” he said. “We’ve had a number of conversations with other carriers.”

He said customers of HealthyCT and UnitedHealthcare will be receiving letters in the coming weeks notifying them that they will have to choose a new carrier during the open enrollment period. Customers who did not opt for automatic annual enrollment will also be reminded about the sign-up period.

Counselors are available to help patients enroll through Access Health CT at community health centers, including UCFS and the Community Health Center in New London and Groton. Patients can also sign up directly through the website www.accesshealthct.com.

j.benson@theday.com