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Chlamydia and Gonorrhea — Two Most Commonly Reported Infectious Diseases in the United States

The Sexually Transmitted Disease Surveillance 2009 Report provides national surveillance data for the reportable sexually transmitted diseases (STDs) chlamydia, gonorrhea, and syphilis.

Sexually transmitted diseases (STDs) remain a major public health challenge in the United States (U.S.) CDC estimates that there are approximately 19 million new STD infections yearly. There were more than 1.5 million total cases of chlamydia and gonorrhea reported to CDC in 2009 — making them the two most commonly reported infectious diseases in the United States. Adolescent girls (15-19 years of age) and young women (20-24 years of age) are especially hard hit by these two diseases. The largest number of reported cases of both chlamydia and gonorrhea in 2009 was among girls of these two age groups. This likely reflects a combination of factors, including biological differences that place females at greater risk for STDs than males, as well as higher STD screening rates among young women.

Syphilis — a disease once on the verge of elimination — began re-emerging as a public health threat in 2001. This is primarily because of a resurgence of the disease among men who have sex with men (MSM), though cases among women have also been increasing in recent years.

Key Findings

Chlamydia remains the most commonly reported infectious disease in the United States. There were more than 1.2 million cases of chlamydia (1,244,180) reported to CDC in 2009, the largest number of cases ever reported to CDC for any condition. Women, especially young and minority women are hardest hit by chlamydia. CDC recommends annual chlamydia screening for young women under the age of 26.

There were 301,174 reported cases of gonorrhea in 2009, a 10 percent decline from the past year— making gonorrhea the second most commonly reported infectious disease in the U.S. In 2009, the gonorrhea rate for women was slightly higher than for men. CDC supports recommendations from the U.S. Preventive Service Task Force to screen high-risk sexually active women for gonorrhea.

In 2009, there were 13,997 reported cases of primary and secondary (P&S) syphilis — the most infectious stages of the disease — the highest number of cases since 1995 and an increase over 2007 (11,466 cases). The majority of reported syphilis cases in the U.S. continue to be among MSM. CDC recommends that sexually active MSM be tested at least yearly for syphilis (and other STDs).

STDs and Infertility
Untreated STDs can lead to serious long-term health consequences, especially for adolescent girls and young women. CDC estimates that undiagnosed and untreated STDs cause at least 24,000 women in the U.S. each year to become infertile. Expanded access to STD prevention services, screening, and treatment is urgently needed to reduce the toll of STDs and protect the health of millions of Americans.

Racial Disparities
Racial minorities continue to face severe disparities across all three reportable STDs. While racial disparities persist overall, African-Americans, especially young African-American women, are the most affected. Young African-American women face significantly higher rates of chlamydia and gonorrhea than any other group, while the highest rates of syphilis are among African-American men.


For STD Awareness Month 2011, CDC is urging STD screening among young people particularly young people aged 15-24 years as they account for nearly half of the 19 million new STD cases each year. Screening is one of the most effective, yet underutilized, tools to identify and treat those who are infected and to help prevent the further spread of STDs.

Treatment of STDs is essential, both to prevent serious health consequences for those who are infected and to reduce the further spread of disease. When detected early, treatment is relatively simple. It is important for partners of those infected to be evaluated and treated to prevent both re-infection and the spread of disease.

The most reliable ways to avoid infection with an STD are to abstain from sex (i.e., oral, vaginal, or anal sex) or to be in a long-term, mutually monogamous relationship with an uninfected partner. Consistent and correct use of the male latex condom reduces the risk of STD and HIV infection. Expanded access to proven behavioral interventions to reduce the risk of contracting STDs, particularly those tailored for adolescents, MSM, and African-Americans at greatest risk, is an important component of the nation’s response.

It is critical to reduce the severe racial disparities in STD rates, especially for African-Americans. This will require increased awareness among affected communities of the importance of this problem, as well as a strong public health response to ensure that minority communities have access to prevention, screening, treatment, and partner services. Expanded access to care would be an important contributor to addressing this problem.

Chart: Chlamydia—Rates by Sex, United States, 1990-2009

Data Source

Centers for Disease Control and Prevention. Sexually Transmitted Disease Surveillance, 2009. Atlanta, GA: U.S. Department of Health and Human Services; 2010.

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