One in nine prisoners in Colorado has hepatitis C, the most deadly — though curable — infectious disease in the United States, yet only a fraction of them receives treatment.

Of the 2,280 prisoners diagnosed with the virus, the Colorado Department of Corrections treats fewer than 70 per year, leaving the rest to suffer as victims of a “cruel and arbitrary” system, ACLU Colorado accused in a class-action lawsuit filed Wednesday against the department.

Before a prisoner is considered for treatment, a blood test must show “sustained measurable liver damage” serious enough to equate roughly to stage two liver disease, which is measured in stages zero through four. Then the prisoner must complete alcohol or drug therapy, which can take more than two years depending on program availability at the prison where the inmate is held.

The chances of receiving potentially life-saving anti-viral medication even after those qualifications are met is minimal. A Department of Corrections committee that meets four times each year chooses a “select few” prisoners based on a yearly quota of up to 70 people, the lawsuit says. A recent count found 735 prisoners eligible for consideration by the committee.

“We have always been concerned with the delivery of medical care in the Department of Corrections and this is a giant health crisis in Colorado prisons and the nation’s prisons,” said Mark Silverstein, legal director for ACLU Colorado. Also, when prisoners don’t receive treatment behind bars and are released, it raises the public health risk of spreading the disease, he said.

Department of Corrections spokesman Mark Fairbairn said the prison system has treated 80 offenders with the new antiviral treatment since July 2015. In all but one case, the prisoners were cured, he said. “Although these new pharmaceuticals are groundbreaking and effective, we have developed and implemented policy to assess treatment needs alongside appropriated resources,” he said in an email.

It was not known how much it would cost the state to provide treatment for all infected prisoners or how much it has cost to treat those 80 offenders.

The ACLU Colorado filed a similar lawsuit in 2016 against the state Medicaid department, accusing Colorado of denying treatment for needy Coloradans infected with the curable disease.

Until 2013, the best treatment for hepatitis C included toxic injections that went on for a year, had an estimated cure rate of only 50 percent and had side effects worse sometimes than the disease itself — bone pain, memory loss, depression and nausea. Sovaldi, approved four years ago, is something of a miracle drug, requiring three months of therapy without the excruciating side effects. Its cure rate is 90 percent.

But because of the drug’s price tag — up to $30,000 to $40,000 for the 12-week regimen — Medicaid placed stipulations on who qualifies for treatment. Those with the government insurance must have enough liver damage to qualify as stage two.

That lawsuit against the state Medicaid department is ongoing.

The new lawsuit filed Wednesday is brought by four prisoners, including Robert Wieghard, a 61-year-old Bent County Correctional Facility inmate. Wieghard has enough liver damage to qualify for treatment, but has been denied eligibility because he has not completed the required alcohol and drug classes.

Wieghard was transferred in 2016 to a Buena Vista prison so he could attend the required program, which was not offered at the Arkansas Valley prison where he was held previously. But because he has a disability and could not climb the stairs at the Buena Vista prison, he was sent to Bent County, which does not offer the program he was told to complete in order to become eligible for treatment to cure his hepatitis, the lawsuit says.

Another prisoner with hepatitis C, 52-year-old David Poole, is suffering from declining health, including a bloated abdomen and a rash. “His entire body itches constantly,” says the lawsuit. “When he scratches his skin, he develops open sores, and he is concerned about the risk of spreading his (hepatitis C) infection as a result.”

The lawsuit alleges Department of Corrections medical staff have “incorrectly calculated” Poole’s hepatitis C level and erroneously denied him treatment.

It says hepatitis C has contributed to 18 deaths of Colorado prisoners in the last three years. The virus is the most deadly infectious disease in the United States, leading to cirrhosis and liver failure if not treated, according to the Centers for Disease Control and Prevention. It’s transmitted mainly by blood, through shared needles, and rarely through sexual contact.

The lawsuit seeks treatment for the prisoners named as well as current and future prisoners diagnosed with hepatitis C.

It quotes from a 2016 email from the department’s chief medical officer, Susan Tiona, to then-Sen. Pat Steadman, a Denver Democrat and state budget writer. The email says the department planned to provide hepatitis C treatment to 20-25 prisoners per year and eliminate Colorado prison deaths from hepatitis C “within the next decade.” The lawsuit refers to those calculations as “chilling.”

The yearly quota was raised to 70 prisoners per year, but it still would take more than a decade to treat the 735 prisoners who have qualified to have their cases heard by the department’s committee, according to the ACLU.

Colorado officials “deliberately adopted a budget” that fails to treat prisoners with hepatitis C and then created policies designed “to delay and deny necessary medical treatment to all but a small fraction” of infected inmates, the lawsuit says.

Similar lawsuits against prison systems are pending in seven other states, including Florida and Missouri.