Thanks,
Trying to make a more informed decision.

Dear Trying to make a more informed decision,

You're doing an excellent job of looking out for your health and being a responsible sexual partner. Many people have run up against the frustration of fuzzy answers regarding sexually transmitted infections (STIs), testing and safer sex — there are few "truths," significant complexity, and lots of gray area. It sounds like you are off to a great start: talking with your partner about sexual histories, birth control, and STI testing. Limiting your number of lifetime partners, using condoms and other barrier methods, and getting tested for STIs with new sexual partners will also help you reduce risk. But, in the end, sex involves some risk, so you and your partner have to figure out what you're comfortable with.

Testing for STIs involves weighing risks, probabilities, and costs, because testing everyone for everything would be very expensive and is much more likely to result in "false positives" (where you test positive, but you don't have the infection). For viral infections like herpes and HPV that come and go on their own, it's difficult to test when symptoms aren't present because the most accurate tests use samples from the lesions the virus causes. It makes more sense for medical providers to make diagnoses based on a combination of information including your sexual history, symptoms and testing (if necessary).

You asked about the number of infections among the general public. Before we get to the numbers, a warning: It's difficult to measure prevalence (how many people have the infection), because many times infections are asymptomatic so people don't get tested. Also, different infections have different reporting requirements so, for example, information is gathered much more systematically for chlamydia and gonorrhea than for herpes.

Because information is reported in different ways, it can be difficult to compare one statistic to another. Also, prevalence differs significantly among subpopulations (based on age, ethnicity, gender, sexual orientation, geography, etc.) So, for example, even though in any given year only .3% of people in the U.S. might have a chlamydia infection, it's one of the most common STIs among young people. In 2005, the CDC reported that of women screened in selected family planning clinics, the proportion of positive tests was 6.3% among 15-24 year olds. To think about it another way, according to one study, Trichomoniasis, HPV, and Chlamydia accounted for 9 out of 10 new STI infections among 15-24 year olds in 2000.

Thus, knowing the prevalence in the general population may not be your best guide, either for judging what to test for or what to watch out for. This may explain why it's hard to find clear guidelines about testing or overall population statistics — good medical providers make informed judgments based on each person's situation, and data about different subpopulations. That said, here are some general prevalence numbers for common STIs and information about testing. The following data are from a Kaiser Family Foundation 2003 report.

Trichomoniasis — This is the most common curable infection in young women, with an estimated 5 million new infections annually in women and men, or 1.5% of the total population. Diagnosis is made through visual examination and laboratory test. Prescription drugs are available to treat trichomoniasis.

Bacterial Vaginosis (BV) — This is the most common bacterial infection among women of childbearing age. Overall prevalence is unknown, but as many as 16% of pregnant women have BV. BV is diagnosed by clinical exam and lab test. BV can be sexually transmitted, but is also an infection that can occur from non-sexual causes (such as an imbalance in the pH of the vagina). Regardless, a BV infection can be treated with antibiotics.

Human Papillomavirus (HPV) — Some strains of HPV cause genital warts and some strains are associated with cervical cancer. Genital HPV is thought to be the most common STI in the U.S. — 50-75% of sexually active people will acquire it at some point in their lives. Although there is no cure, it appears the body often clears the virus on its own. An HPV vaccine was introduced in 2006 that protects against four strains of HPV that cause warts or are linked to cancer. Medical providers mainly diagnose HPV based on the presence of warts or, for women, an "abnormal" Pap test. If a Pap test has an abnormal or unclear reading, it may be followed up with a colposcopy and/or an HPV test. (Pap tests look for cell changes caused by HPV infection, the HPV tests looks for the virus itself.) Because HPV is fairly common, usually goes away on its own, and has no cure, it isn't particularly useful to do an HPV test unless you have an abnormal Pap. There is currently no test for HPV in asymptomatic men. When HPV has led to symptoms, treatment options include different methods of removing genital warts or HPV lesions on the cervix.

Herpes — One out of five adults and adolescents has had Herpes Simplex Virus 2 (genital herpes). Like HPV, herpes is difficult to diagnose without visible sores, and the majority of infected people never notice symptoms. Although there's no cure, a person with active herpes can use daily medication to reduce the likelihood of transmission to a sexual partner. A blood test is available but it isn't always conclusive, so it's not usually done unless someone has symptoms or suspects an exposure.

Chlamydia — It's estimated that 3 million cases occur annually in the U.S. That's 3 per 1000 people, or less than .3% of the population. Approximately 75% of infected women and 50% of infected men have no symptoms. Testing can be done with a swab test in the penis, vagina, anus or throat. Some clinicians use a urine test rather than a penis swab. Chlamydia can be treated with antibiotics.

HIV — One 2006 study from the Centers for Disease Control estimates an overall prevalence of HIV in the United States at about .2% - that is, 2 out of every 1000 people, or around 900,000 people all together. Again, prevalence numbers are significantly different depending on factors such as your ethnicity, where you live, and age. HIV testing can be done with a blood test or a mouth swab. It may take up to 3-6 months after exposure to the virus for your body to develop the antibodies that are measured by the test, so even if you have HIV you might not test positive right away. If you are concerned about exposure to HIV, you may want to consider getting tested now and again in a few months.

Hepatitis B — There are approximately 1.25 million people in the U.S. with chronic Hep B, or .4% of the population. Hep B is incurable, but there is a vaccine to prevent it. It's diagnosed with a blood test.

Gonorrhea — Each year, approximately 650,000 or .2% of the population is infected with gonorrhea. In 1999, 77% of all reported gonorrhea cases occurred among African Americans, and 75% of all reported gonorrhea is found in people ages 15-29. Testing for gonorrhea and chlamydia are most often done simultaneously, with a swab test in the penis, vagina, anus or throat. Gonorrhea, wherever it is present, can be treated with antibiotics.

Numbers, numbers, numbers, and really all you want is a straightforward answer: "Should I use this condom, or not???" If only the answer were so simple… as you probably realize, the only way to be 100% certain you don't get any infections is to not have any oral, vaginal, or anal sex. Most people eventually decide to take the plunge and explore the joys of sex. At that point, communication and cooperation between you and your partner(s) and your medical provider becomes crucial for keeping things as safe as possible.

It's also important to realize that many STIs are treatable or curable. If you are concerned about infection, it's a good idea to get tested. Students at Columbia can make an appointment at Primary Care (call x4-2284 or log on to Open Communicator), or with the Gay Health Advocacy Program (GHAP) for confidential HIV testing, counseling and treatment. Outside of Columbia, you can visit your primary care provider, or a health center such as Planned Parenthood for testing. It's good to be careful, and also good to be able to relax and enjoy your sexuality — hopefully the two can go hand in hand!

Alice

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