New research shows that rates of throat, mouth, and anal cancers are rising rapidly among men due to the spread of HPV (human papillomavirus), a highly contagious sexually transmitted infection. HPV is virtually undetectable in guys – until they come down with cancer, says Dr. William Schaffner, chairman of the Department of Preventive Medicine at Vanderbilt University. HPV vaccines like Gardasil can safeguard against the disease, but men need to be vaccinated before they reach their thirties – at which point half have already been exposed to the virus. You can keep your kids safe by vaccinating them before they hit puberty, but to best protect yourself from HPV, "limit your sexual partners, know them well, and always use protection," Schaffner says. Also, give up cigarettes. "Smoking and HPV are interactive risk factors for some of these cancers, so quitting cuts your chances even if you have HPV," he says.