More than 1.2 million cases have been officially reported, the largest number of cases for any of the diseases that must be reported to the CDC.
Because chlamydia infections usually don’t cause symptoms until they result in pelvic inflammatory disease, many cases remain undetected and hence unreported. Sexually active girls and women under age 26 should be screened for chlamydia every year, but only 41.6% of eligible women enrolled in Medicaid or private health plans do so.
Chlamydia rates are three times higher in women than in men and eight times higher in African-Americans than in whites.
Left untreated, some 10% to 20% of chlamydia infections cause pelvic inflammatory disease. That can lead to long-lasting pelvic pain, ectopic pregnancy, and infertility. Every year, the CDC estimates, chlamydia and other STDs leave at least 24,000 U.S. women unable to bear children.
Girls ages 15 to 19 have the highest chlamydia rate: 3,276 cases per 100,000 females. The rate is only a little lower in women ages 20 to 24: 3,180 cases per 100,000 females.
Overall, chlamydia rates went up 9.2% from 2007 to 2008, the most recent year for which there is data. Some of the increase is due to increased screening, but the CDC suspects that much of the increase reflects a rising number of new infections.
Chlamydia rates ranged from state to state, with rates highest in Mississippi and Alaska (each with more than 700 cases per 100,000 population) and lowest in New Hampshire, West Virginia, Vermont, and Maine (each with under 200 cases per 100,000 population.
However, 57% of chlamydia cases are in cities. Here’s the ranking, by chlamydia rate, of the 50 largest metropolitan areas in the U.S.:
|Metropolitan Statistical Area||2008 Cases||2008 Rate
|Virginia Beach-Norfolk-Newport News, Va.-N.C.||8,789||1,036.3|
|Austin-Round Rock, TX||5,933||760.4|
|San Antonio, TX||7,206||709.7|
|Kansas City, MO-KS||7,115||703.7|
|St. Louis, MO-IL||10,166||702.3|
|New Orleans-Metairie-Kenner, LA||3,722||694.3|
|San Diego-Carlsbad-San Marcos, Calif.||10,257||692.7|
|Oklahoma City, Okl.||4,119||681.3|
|Dallas-Fort Worth-Arlington, TX||20,125||658.5|
|Las Vegas-Paradise, NV||5,842||647.7|
|Houston-Baytown-Sugar Land, TX||17,287||615.4|
|U.S. MSA TOTAL||501,750||607.0|
|Los Angeles-Long Beach-Santa Ana, CA||38,100||587.7|
|New York-Newark-Edison, NY-NJ-PA||56,829||584.9|
|Tampa-St. Petersburg-Clearwater, FL||8,099||579.4|
|Hartford-West Hartford-East Hartford, CT||3,474||569.4|
|Atlanta-Sandy Springs-Marietta, GA||14,898||557.9|
|San Francisco-Oakland-Fremont, Calif.||11,514||544.5|
|Riverside-San Bernardino-Ontario, Calif.||10,009||490.9|
|San Jose-Sunnyvale-Santa Clara, Calif.||4,218||478.8|
|Miami-Fort Lauderdale-Miami Beach, Fla.||13,144||472.6|
|Minneapolis-St. Paul-Bloomington, Minn.-Wis.||7,037||436.5|
|Salt Lake City, Utah||2,254||417.0|
|Providence-New Bedford-Fall River, R.I-.Mass.||3,327||402.3|
|Milwaukee-Waukesha-West Allis, Wis.||1,116||141.3|
Chlamydia isn’t the only STD on the rise. Once on the verge of being eliminated from the U.S., syphilis is making a comeback. Syphilis rates are up 67% since 2004,and jumped 18% from 2007 to 2008. Driving the syphilis comeback are infections among men who have sex with other men, who make up 63% of cases, but heterosexual syphilis is on the rise, too. The CDC reports the data in its “National Overview of Sexually Transmitted Diseases (STDs), 2008,” released Nov. 16, 2009.