Trivia: STDs/STIs

Most types of STDs can be prevented through safer sex practices, and vaccines are available for hepatitis B and HPV, which is a cause of cervical cancer. Many STDs can be cured if diagnosed in the early stages. Left untreated, STDs can cause morbidity, greater susceptibility to HIV and other STD infections, infertility, complications in pregnancy, and harm to the newborn.

Risk factors for developing STDs include living in urban areas, low socioeconomic status, illicit drug use, prostitution, and promiscuity. Adolescent females are especially vulnerable to STDs. Furthermore, many women who are infected with an STD remain asymptomatic, and are thus more likely to remain undiagnosed and pass the disease to their partners.

Common STDs

HIV and AIDS: In 2007, 33.2 million people worldwide were estimated to be living with HIV, and 2.5 million people became newly infected with the disease.

Trichomoniasis is caused by the protozoan parasite Trichomonas vaginalis. The WHO estimated that there were 173.46 million new cases of trichomoniasis worldwide in 1999.

Chlamydia is caused by Chlamydia trachomatis bacteria, and is one of the most common STDs. The WHO estimated that there were 91.98 million new cases of chlamydia worldwide in 1999.

Gonorrhea is caused by Neisseria gonorrhoeae bacteria. The WHO estimated that there were 62.35 million new cases of gonorrhea worldwide in 1999.

Syphilis is caused by the Treponema pallidum spirochete. The WHO estimated that there were 11.76 million new cases of syphilis worldwide in 1999.

In 2006, the rates of chlamydia, gonorrhea, and syphilis rose in the United States. According to a November 2007 Reuters news item, there were more than 1.03 million new chlamydia cases in 2006 – the highest number of annual cases for any STD. (Since chlamydia is often asymptomatic and many patients remain undiagnosed, the CDC estimates that 2.8 million new infections may be occurring each year.) In the same year, 358,366 new cases of gonorrhea and 9,756 new cases of syphilis were reported.

Genital herpes is caused by herpes simplex virus type 2 (HSV-2). In the US, it's estimated that 40 to 60 million people are infected with HSV-2, with an incidence of one to two million infections and 600,000 to 800,000 clinical cases per year. In developing countries around the world, the prevalence of HSV-2 varies from two to 74%.

Human papillomavirus (HPV) is the leading cause of cervical cancer. However, most HPV infections do not cause illness. In the United States, an estimated 75% of people aged 15 to 50 become infected with HPV at some point in their lifetime, and the global prevalence of genital HPV infection is about 440 million. About 40 different types of HPV viruses can infect the upper digestive and anal-genital tracts. Some "low-risk" types of HPV, such as HPV-6 and HPV-11, may cause genital warts. High-risk types of HPV, such as HPV-16 and HPV-18, may cause lesions which can regress on their own, or develop into cervical cancer.

New Findings

Several human trials of HIV vaccines have produced disappointing results. According to a Forbes article, Merck's V520 HIV vaccine did not decrease the risk of contracting HIV and failed to slow the progression of HIV infection to AIDS. The vaccine used an adenovirus – a type of cold virus – to deliver three HIV genes, in the hope that it would prime the immune system to attack the HIV virus upon infection. Forty-nine out of 914 vaccinated men contracted HIV, compared to 33 out of 922 men who had received a placebo shot. Men with a high level of immunity to adenovirus may have become more susceptible to HIV infection following vaccination: Of the 778 men with high levels of adenovirus immunity, 21 vaccinated individuals were HIV+, compared to nine in the placebo group. The trial was discontinued in September of 2007 following these findings.

Several other HIV vaccines used recombinant adeno-associated virus (rAAV), and small human trials were discontinued when the vaccines showed no protective effects. A paper published on December 3, 2007 in The Journal of Clinical Investigation found that these vaccines may actually weaken the body's natural immune response to HIV infection.

A survey of Canadian teens, published in the January 2008 issue of Paediatrics and Child Health, found that sexually active teens needed more information regarding STDs. Many of the respondents were unaware of some common STDs such as Chlamydia, 69% said they could not find information they were looking for about sex, and 5% of sexually active respondents had been diagnosed with an STD. The study included 1,171 teens aged 14 to 17, and found that 27% of respondents were sexually active. Among the sexually active teens, 76% had used a condom the last time they had sex.

A significant percentage of patients who are diagnosed with an STD will develop a second infection within one year, according to a study from the October 17, 2006 issue of Annals of Internal Medicine. After being diagnosed with an STD, 2,419 subjects from three STD clinics were followed for one year, and screened for Chlamydia, gonorrhea, and trichomoniasis every three months. During that time, 25.8% of women and 14.7% of men developed a new infection, and 66.2% of infected patients reported no symptoms.

For more information, see: • American Social Health Association • CDC – Sexual Health • Public Health Agency of Canada – Sexual Health and Sexually Transmitted Infections

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