Sexually transmitted diseases are on the rise across El Paso County, troubling public health officials even as the reasons for their spread remain unclear. Rates of chlamydia, gonorrhea and even syphilis - a rare disease in the United States just 20 years ago - have surged in recent years. The increases mirror a nationwide trend that the Centers for Disease Control and Prevention warned last fall is a "growing threat" that is outpacing the agency's ability to respond. "It's very significant and worrisome," said Dr.