400K Americans Have Chlamydia, Don't Know It

Hundreds of thousands of Americans—especially black teenage girls—have a disease that could leave them infertile but don't know it, federal health officials warn. Researchers say that around 1.7% of men and women aged 14 to 39 have chlamydia, which adds up to 1.8 million cases nationwide, but only 1.4 million cases have been reported, leaving around 400,000 undiagnosed cases of the sexually transmitted disease, reports WebMD. The disease can do serious damage to women's reproductive systems but is often symptomless, Fox notes.

"Young women continue to bear a disproportionate burden," Centers for Disease Control and Prevention researchers say in a press release, explaining that there is a chlamydia prevalence of 6.4% among sexually active adolescent girls aged between 14 and 19—but with a major racial disparity. The rate is 18.6% among black teenage girls, compared to 3.2% among white girls. The researcher says the study shows the need for regular screening of sexually active teen girls, with targeted intervention for those most at risk. (More sexually transmitted diseases stories.)