Just in time for Valentine’s Day, researchers from the U.S. Centers for Disease Control and Prevention issued two new studies of sexually transmitted infections (STIs) today detailing what the lead author of one calls “an ongoing, severe, STI epidemic.”

The studies reveal new infection data, some of it available for the first time, for the eight most common STIs — chlamydia, gonorrhea, syphilis, herpes, human papillomavirus (HPV), hepatitis B, HIV, and trichomoniasis. The studies, which estimate infection rates and medical costs related to STIs, were published in the journal Sexually Transmitted Diseases.

Both are startling. In 2008, there were 20 million new incidents of infection in the United States, and a prevalence (new infections plus ongoing infection) of 110 million, according to CDC estimates. (Because one person may have more than one infection, the 110 million figure does not mean 110 million people have a sexually transmitted disease.) As a result, the United States incurred estimated direct medical costs of nearly $16 billion.