Medicaid expansion in the states. (Kaiser Family Foundation, as of March 26, 2014)

States that refused to expand Medicaid under the Affordable Care Act are experiencing a boom in enrollees anyway, growth a new report attributes to increased awareness surrounding the health-care law.

In 17 of the 26 states that did not expand Medicaid, more than 550,000 new individuals signed up for coverage under Medicaid during the first quarter of 2014, according to Avalere Health, the company that produced the study. That represented a 2.8 percent average increase in state Medicaid rolls.

Avalere said the new enrollees were previously eligible for Medicaid but hadn’t signed up. They were likely spurred to apply for benefits after hearing about their eligibility, which the company dubbed the “woodwork effect.”

The states receive federal funding for the new enrollees through 2016, but only at standard rates. States that expanded their Medicaid rates receive more federal compensation for new enrollees.

“Many of these non-expansion states that politically oppose the ACA are now facing unexpected financial and operational pressure due to woodwork enrollment,” Caroline Pearson, Avalere’s vice president, said in a statement.

That means states that decide against accepting federal dollars to expand Medicaid are paying for their decisions.

More than 98,000 new enrollees signed up for coverage in Georgia, and more than 50,000 individuals signed up in North Carolina, Tennessee and South Carolina, the report found. Montana saw 14,100 new Medicaid patients sign up in the first three months of 2014, a 10 percent increase of the state’s Medicaid rolls. Idaho, Kansas and New Hampshire also saw their rolls grow more than 5 percent.

New Hampshire, Michigan and Pennsylvania have all decided to expand their Medicaid programs, at least temporarily, but those expansions had not taken effect during the first three months of the year. Michigan expanded its Medicaid program in April, while New Hampshire’s expansion begins in July. Pennsylvania plans to expand its Medicaid program in 2015.

Seven states reported decreases in the number of Medicaid enrollees, according to data from the Centers for Medicare and Medicaid Services.