Infection with the dangerous bacteria MRSA is on the rise among people who inject drugs, according to the Centers for Disease Control and Prevention (CDC).

People who inject heroin and other drugs are 16 times more likely than other people to develop severe illnesses from MRSA, the CDC reported.

MRSA, or methicillin-resistant Staphylococcus aureus bacteria, can live on the skin without causing symptoms. But the bacteria can become dangerous if it enters the bloodstream, where it can destroy heart valves or cause other serious health problems. An estimated 11,000 people die from MRSA-related causes in the United States every year, the Associated Press reports. In 2016, 9 percent of MRSA cases involved injection drug users, compared with 4 percent in 2011.

MRSA “is on the skin, and as the needle goes into the skin it brings the bacteria with it,” said study co-author Dr. Isaac See.