Chlamydia, Syphilis, and Gonorrhea - Oh My! Chlamydia and syphilis cases have increased, while the number of gonorrhea infections remains constant, according to the latest report by the CDC. The study found that reported cases of chlamydia in the United States reached an all-time high of 1.1 million in 2007, the latest year for accurate data. Syphilis, which was all but eradicated in the U.S. a decade ago, infected 11,000 new people that same year. Gonorrhea is holding steady, at about 365,000 cases. The good news is that all of these sexually transmitted diseases are treatable with antibiotics and largely preventable through safe sex. The bad news is that the actual numbers may be much higher due to under reporting and under screening.