A team at the University of Florida, Baylor College of Medicine and elsewhere found that 11.5 percent of U.S. men were actively infected with oral HPV between 2011 and 2014, and 3 percent of women were. That adds up to 11 million men and 3 million women, the researchers report in the Annals of Internal Medicine.

It’s a sexually transmitted infection and the more sex partners someone had, the bigger their risk. But the study found smoking also increased the danger of a high-risk infection, and, perhaps surprising to some, that men and women alike who smoked marijuana were far more likely to develop a cancer-causing strain of HPV.