Certain high-cost drugs are straining state budgets. A new deal approved Wednesday allows Louisiana to spend a fixed amount for unlimited access to a costly cure. Other states may try to follow suit.

As the number of people who inject drugs and share needles has soared, the rate of infection with hep C has climbed, too. Yet many drug treatment patients aren't tested for the liver-damaging virus.

About a dozen states have added hepatitis C to the list of medical conditions for which people can face criminal prosecution if they knowingly engage in activities that could spread the disease.

Treatment for hepatitis C has improved dramatically in the last decade — so much so that it drew one doctor out of retirement to help make sure more low-income patients are cured.

From 2010 to 2015, the number of new infections leaped nearly 300 percent, according to the Centers for Disease Control and Prevention. And researchers appear confident of the cause.

In 2011, just 41 health care providers prescribed more than $5 million each in medicines under Medicare Part D. In 2015, that number was 514. The rise of expensive hepatitis C drugs is a factor.

Now that there are better treatments for hepatitis C in adults, doctors hope the drugs soon will be approved for use in children who were infected at birth. But many at-risk infants don't get tested.

Private insurers billed California $387.5 million to treat just 3,624 patients with new medications for hepatitis C. The people are covered by the state's Medicaid program.

A Senate investigation finds that Medicaid programs in 33 states spent more than $1 billion on the hepatitis C drug Sovaldi in a single year.