Rates of chlamydia and syphilis infection continue to rise among US individuals, according to an annual report from the national Centers for Disease Control and Prevention (CDC) (http://www.cdc.gov/std/stats07/).
In 2007, 1.1 million diagnoses of chlamydia were reported to the CDC, a 7.5% increase since 2006, when 1.0 million cases were reported. The agency notes, however, that half of all cases go undiagnosed, and estimates that there were actually 2.8 million new cases of chlamydia in 2007.
Kuehn BM. Sexually Transmitted Infections. JAMA. 2009;301(8):817. doi:10.1001/jama.2009.197