About seven years ago, Colorado Springs resident Carleen McGuffey got shocking news: She had hepatitis C, a serious liver disease caused by a blood-borne RNA (ribonucleic acid) virus, which she contracted either from a blood transfusion or intravenous drug use, both long in her past. But then she made an even more surprising decision: “I didn’t get staged or treated because the old medicines were very harsh, and I was pregnant, caring for, or nursing my children,” says the 45-year-old mother of six.

What makes McGuffey notable isn’t her decision not to get treated right away: It’s that she knew she was infected. About 70,000 Coloradans have hepatitis C, which is now the most common blood-borne infection in the United States. It claimed more lives across the country in 2013 than HIV, pneumonia, and tuberculosis combined. Symptoms of hep C range from fever and fatigue to joint pain and jaundice, and left untreated, hep C can lead to liver cancer—yet the Centers for Disease Control and Prevention estimate that more than half of afflicted people don’t know they have it. “Hepatitis C is often known as the ‘silent killer,’ in that most people don’t show symptoms for 20 or even 30 years,” says Andrés Guerrero of Colorado’s Department of Public Health and Environment. “The infection usually progresses very slowly and causes damage to the liver—long before someone realizes something is wrong.”

The growing opioid epidemic is driving a new wave of the disease because the virus can live for up to three weeks on needles. Worse still, a recent report from Denver’s Center for Improving Value in Health Care suggests that 90 percent of infected Coloradans are going untreated, due in part to the cost of medicine (though many insurance companies cover hep C meds) and a lack of access to trained providers, especially in rural areas. The good news: New treatments have been more than 95 percent successful in curing hep C, and two additional medications (Zepatier and Viekara) were released in 2016. “As more medications come to market, we see a small downward trend in cost,” Guerrero says.

Since complications from a liver biopsy nearly took her life in 2013, McGuffey’s family members have been raising awareness to promote testing and fight the stigma of hep C through their nonprofit, Climbing for Carleen. She shares her story to encourage others to be proactive, and her husband, James, began climbing fourteeners (including Pikes Peak in a liver costume) with their 13-year-old son to draw attention to the cause. “If it’s one life that we save from hep C, it will have been worth it,” James says. “Even if it’s just one.”