Connecticut-based health insurance giant Aetna added to the drumbeat of woes for the nation's health insurance exchanges on Monday evening by announcing exits from most of the 778 counties where it currently competes.

Aetna will continue to sell exchange policies in 242 counties across four states -- Delaware, Iowa, Nebraska and Virginia.

The exchanges are part of the individual market, where individuals and families that don't have access to employer-sponsored insurance or government programs buy coverage. It doesn't include Medicare shoppers.

Aetna says it has lost more than $430 million in the individual market since January 2014.

In a statement, chief executive Mark Bertolini said: "More than 40 payers of various sizes have similarly chosen to stop selling plans in one or more rating areas in the individual public exchanges over the 2015 and 2016 plan years, collectively exiting hundreds of rating areas in more than 30 states. ... We regret having to make this decision."

The U.S. Department of Health Human Services says that other health insurers remain committed to the exchange markets. Federal officials say they've taken several steps in recent months to improve the exchanges, including tighter rules around special enrollment periods and more outreach efforts to attract younger and healthier subscribers.

The exchanges were launched for 2014 as part of the federal Affordable Care Act (ACA).

"Aetna's decision ... does not change the fundamental fact that the [exchanges] will continue to bring quality coverage to millions of Americans next year and every year after that," said Kevin Counihan, the top federal official for the exchanges, in a statement. "The ACA marketplace is serving more than 11 million people and has helped America reach the lowest uninsured rate on record."

Minnetonka-based UnitedHealthcare last year announced a big pullback from the exchanges, saying this spring it would leave in 2017 government-run marketplaces in 30 of 33 states where it currently competes. Neither UnitedHealthcare nor Aetna has ever sold on Minnesota's MNsure exchange, but the local marketplace has seen disruptions, too.

Golden Valley-based PreferredOne withdrew from MNsure after suffering big financial losses in 2014. This summer, Eagan-based Blue Cross and Blue Shield of Minnesota announced it would stop selling individual market policies -- both on and off the MNsure exchange -- that currently cover more than 100,000 people.

Blue Cross of Minnesota says it will sell for 2017 only HMO plans with tighter networks of doctors and hospitals in the individual market.

Read Aetna's announcement here.

The story continues.