text: how many people a year are affected by sexualy transmitted disease?   chlamydia remains the most commonly reported infectious disease in the united states. in 2004, 929,462 chlamydia diagnoses were reported, up from 877,478 in 2003. even so, most chlamydia cases go undiagnosed. it is estimated that there are approximately 2.8 million new cases of chlamydia in the united states each year  gonorrhea is the second most commonly reported infectious disease in the united states, with 330,132 cases reported in 2004. from a high of 467.7 cases per 100,000 population reported in 1975, the u.s. gonorrhea rate fell to 113.5 in 2004 (a 76% decline) — the lowest recorded level since reporting began in 1941. more recently, from 2003 to 2004, the rate fell 1.5 percent (from 115.2 cases per 100,000 population to 113.5). like chlamydia, however, gonorrhea is substantially under diagnosed and under reported, and approximately twice as many new infections are estimated to occur each year as are reported.  syphilis: cases increase for fourth consecutive year the rate of primary and secondary (p&s) syphilis — the most infectious stages of the disease — decreased throughout the 1990s, and in 2000 reached an all-time low. however, over the past four years the syphilis rate in the united states has been increasing. between 2003 and 2004 alone, the national p&s syphilis rate increased 8 percent, from 2.5 to 2.7 cases per 100,000 population; during this time, reported p&s cases in the united states increased from 7,177 to 7,980.   wow was that person ever guessing get the facts...