Nearly one in five inmates entering Pennsylvania prisons has hepatitis C, according to a study published in the June issue of the American Journal of Public health.

'Incredibly high' rate, especially among women

Since 2003, Pennsylvania has screened everyone entering prison for hepatitis C unless an inmate chooses to opt out of the test. Of the more than 100,000 people who were tested upon entry between 2004 and 2012, about 18 percent tested positive for the virus.

"It's an incredibly high rate," said lead author, Sarah Larney, who's a fellow at the National Drug and Alcohol Research Center at the University of New South Wales and a research associate at Brown University.

Larney contrasted that prevalence with that of the general population, where less than 2 percent of people are affected.

Although making up a much smaller percentage of the prison population, female inmates are more likely to have hepatis C, with about one in three screening positive.

The study didn't assess risk factors, or break down prevalence by race and ethnicity, but Larney thinks women "are more likely to have a history of injection drug use and other indicators of poor health than men in prison."

Making a case for universal screening in prisons

Hepatitis C is often referred to as the silent epidemic. Many are unaware they're infected, as symptoms may not appear for years. Untreated, the virus can lead to liver disease and cancer. It's the most common blood-borne disease in the U.S, and is mainly spread through sharing needles and through blood transfusions received before 1992.

Baby boomers are disproportionately affected, so the Centers for Disease Control and Prevention now recommends anyone born between 1945 and 1965 get tested for the virus. That's in addition to those at high risk of exposure, past or present.

Dr. Nicholas Scharff, the recently retired medical director for the Pennsylvania prison system, said this new study counters the CDC recommendation for universal screening just for baby boomers when it comes to the prison population. The study found that most inmates who screened positive for hepatitis C in the state were younger.

"This study showed that, in the first place, if you restricted testing just to baby boomers, you would miss more than half the cases [among those entering prison] in Pennsylvania," he said.

The prevalence of hepatitis C among incoming male inmates in Pennsylvania remains high, though it has gone down slightly over time, mirroring general population trends, Scharff said. Among women, the rate consistently hovers around 30 percent.

While researchers have long known the virus is endemic among prisoners, Larney said that until recently, the data have been outdated or anecdotal, "causing problems in terms of how we address the problem."

Most states test inmates who identify as being high risk or request a test. Pennsylvania is one of about a dozen states that screens everyone unless they choose to opt out. Larney said the study underscores the need for other states to follow Pennsylvania's lead, screening all incoming inmates for hepatitis C.

"We can find very large numbers of people with hepatitis C if we conduct universal screening in prisons, and then we have a really good opportunity to make an impact on the general public health by helping those people stay healthy and to get treatment," said Larney.

A positive hepatitis C test requires confirmatory testing, as anyone who's ever had the virus will screen positive, even if they've been treated or naturally cleared it.

The Pennsylvania Department of Corrections reported treating 60 inmates for hepatitis C in 2013, costing about $1.5 million in total.

For 53-year-old DeAlvin Releford, a Philadelphia resident who was released from state prison last year, the seriousness of hepatitis C is front on his mind.

"A few of my friends died from hepatitis C recently," he said. "The [drug] they were treated with had adverse effects and they didn't have any other option available."

Last winter, a new treatment hit the market that's quicker, more effective but a lot more expensive.