The heroin epidemic is driving up hepatitis C infections, with the biggest increase in people ages 20 to 29, US health officials said Thursday. The number of new infections nearly tripled in five years, to about 2,400 in 2015, the AP reports. The virus is spread by sharing needles to inject drugs, and the increase coincided with a surge in heroin use. But officials at the CDC think the reported infections are only a fraction of the actual number. Most people don't get sick for many years, so they aren't tested and don't know they're infected. The CDC estimates the number of infections in 2015 was 34,000, or twice as many as the 2010 estimate. The hepatitis C virus spreads through the blood but does most of its damage by infecting the liver, which can lead to cirrhosis or liver cancer.
Newer hepatitis C drugs can cure the infection in a few months, but they're pricey—a treatment course can costs tens of thousands of dollars. The CDC also released national hepatitis C death figures, with nearly 20,000 deaths in 2015. The number hasn't changed much recently, but that figure reflects a different group of infected people: baby boomers. The apparent leveling off may be due to a push to test all baby boomers for the virus and treatment improvements, says the CDC's Dr. Jonathan Mermin. Of the 3.5 million Americans living with hepatitis, most were born between 1945 and 1965 and were infected decades ago, per the CDC. Before widespread screening of blood donations began in 1992, the virus was also spread through blood transfusions.