Public health officials are bracing for a wave of hepatitis C infections, one unleashed by the epidemic of prescription painkiller addiction.

The blood-borne virus, on the decline nationally until a few years ago, is rising rapidly among adolescents and young adults, especially in white, rural communities. Those are the same areas where an epidemic of prescription opioid deaths first showed up over a decade ago, followed by a wave of heroin deaths.

Most of the new hepatitis C patients have contracted the virus by injecting drugs, often crushed pain pills.

Scattered studies around the country have detected the patterns, which became clearer with a report released by the U.S. Centers for Disease Control and Prevention.

Less clear but increasingly expected is a rise in the better-known, more-feared virus that often accompanies hepatitis C: HIV. In rural southeastern Indiana, 150 cases of HIV have been identified in the past few months, most of them in a town of 4,200 residents. The vast majority injected drugs. Nearly all were also diagnosed with hepatitis C, which is more easily transmitted by shared needles than HIV.

In the CDC study of disease patterns, the number of new hepatitis C infections among people age 30 and under in Kentucky, Tennessee, Virginia, and West Virginia rose 364 percent from 2006 to 2012; three-quarters of the cases involved injected-drug use. Increases were reported everywhere, but rural and suburban counties went up at double the rate of cities, where the virus historically has circulated more.

Links to drug use, injections

Jon E. Zibbell, a medical anthropologist and lead author of the study, said in an interview that new infections are rising in older Americans as well — up 150 percent overall between 2010 and 2013, the CDC said. But the new study looked beyond hepatitis C infections to patterns of admissions for drug treatment.

The findings “indicate a geographic intersection among opioid abuse, drug injecting, and [hepatitis C] in central Appalachia,” Zibbell and his co-authors wrote. The region has among the nation’s highest rates of fatal overdoses of prescription painkillers.

Hepatitis C can sit silently in the body for decades before causing liver damage so severe in some cases that only a transplant will prevent death. It was transmitted largely through transfusions, surgeries, and injections before effective screening of blood donations began in 1992, heralding a long decline in infections.

Still, at least 3 million people are believed to be chronically infected today, three-quarters of them baby boomers. Most have no idea.

The first medications able to cure hepatitis C with few side effects were approved in 2013 and marketed to the heavily insured over-50 population. They are so expensive that some Medicaid programs for the poor have balked.

With the blood supply safe, intravenous drug use is now the No. 1 source of infection.

Not a baby boomer problem

“This notion that it is just a baby boomer problem is not really accurate,” said Stacey B. Trooskin, an infectious diseases doctor and researcher at Drexel University. “With this resurgence in heroin use with syringes, we are going to start seeing an increase in new cases of hepatitis C and maybe HIV, although less so.”

Although estimates vary widely by age, location, and risk behavior, hepatitis C typically is five times as prevalent as HIV, and it causes more deaths. They often occur in the same people, but the transmission patterns are different.

Hepatitis C is less likely to be passed through sexual contact than HIV. The risk from a dirty needle is the opposite.

Exactly what is in those syringes may be playing a major role in the latest hepatitis C outbreaks in rural areas. Pain pills that are crushed and heated with water are less dissolvable than heroin.

“It’s requiring the users to utilize a higher-gauge needle to inject,” Indiana Health Commissioner Jerome M. Adams said last month. Those needles, if used previously by someone who was infected, will carry more virus than a finer needle used for heroin.

And unlike heroin, a street drug whose potency can’t be predicted, prescription opioids are clearly marked.

When the CDC’s Zibbell investigated a cluster of hepatitis C cases in upstate New York, his team found that users who injected crushed pain pills were five times as likely to test positive for hepatitis C antibodies than those who used other drugs.

The hepatitis C virus can remain alive in the cookers and filters used to prepare drugs for injection again and again.