Sexually transmitted diseases (STDs) are infections acquired by sexual contact. You can catch sexually transmitted diseases any time you have unprotected sex with a partner who is already infected. The organisms that cause sexually transmitted diseases may pass from person to person in blood, semen or vaginal fluids.
It’s possible to contract sexually transmitted diseases from people who seem perfectly healthy — people who, in fact, aren’t even aware of being infected. That’s because many sexually transmitted diseases cause no symptoms, at least at first. The symptoms of several sexually transmitted diseases are also easy to mistake for those of other conditions, so the correct diagnosis may be delayed.
More than 30 viruses, bacteria and parasites cause STDs. Many of these organisms rely almost completely on sexual transmission to survive. In other words, if you have one of these infections, you most likely got it from sexual contact. The microbes include:
- Bacteria that cause gonorrhea (Neisseria gonorrhea)
- Bacteria that cause syphilis (Treponema pallidum)
- Bacteria that cause urethritis, cervicitis and pelvic inflammatory disease (Chlamydia trachomatis)
- Bacteria and intestinal parasites that cause rectal and anal pain, sometimes with severe diarrhea
- Single-celled organisms that cause urethritis, vaginitis, cervicitis and pelvic inflammatory disease (Trichomonas vaginalis)
- Viruses that cause cervical and anal cancer (human papillomavirus, also known as HPV, types 16, 18, 31, 33, 45, 52 and 58)
- Viruses that cause genital herpes (herpes simplex virus, also known as HSV, usually type 2 but sometimes type 1)
Sexual activity plays a role in spreading many other infectious agents, although it’s possible to catch these infections without sexual contact. Viruses capable of spreading both sexually and through close nonsexual contact include the Epstein-Barr virus — responsible for mononucleosis — and a related virus called cytomegalovirus. Hepatitis A, a viral infection usually contracted from contaminated food and water, sometimes passes between sex partners, mainly men who have sex with men. The same pattern of transmission occurs with several common food- and water-borne bacteria and parasites, including shigella, cryptosporidium and Giardia lamblia.
Even between faithful and committed partners, STDs can happen. It’s possible to be infected with herpes, for example, and never realize it, then pass the infection to your long-term partner. More often, though, people get sexually transmitted infections from casual or new partners.
Your risk of catching any STD depends on your sex, age and sexual practices, as well as on the sexual practices and lifestyles of your potential partners. The same factors determine which STDs you’re most likely to be exposed to.
General risk factors include:
Being sexually active. Some activities carry a high risk of transmitting infection. The riskiest activities are anal and vaginal intercourse.
Starting sexual activity at an early age. The possibility of catching an STD or becoming pregnant doesn’t seem real to many adolescents. If they worry about risk at all, they do so after having sex. Also, the younger you start, the more partners you may have.
Having high-risk sex. Vaginal or anal penetration by an infected partner who is not wearing a latex condom transmits some diseases with frightening efficiency. Without a condom, a man who has gonorrhea has a 70 to 80 percent chance of infecting his female partner in a single act of vaginal intercourse. Oral sex is less risky but still too dangerous to chance without a latex condom or dental dam.
Currently having an STD. Being infected with one STD makes it much easier for another STD to take hold. If you’re infected with herpes, syphilis, gonorrhea or chlamydia and you have unprotected sex with an HIV-positive partner, you’re more likely to contract the virus.
Having a history of an STD. If you’ve had one STD, you’re at increased risk of catching another one, partly because you and your potential sex partners often belong to social networks made up of people of similar age, location and background. Within these overlapping networks, couples regularly form, split up and find new partners. If one STD is making its way through such a network, there’s a good chance that others are, too.
Having multiple sex partners, not just concurrently but over time. Every time you break up with one partner and move on to another, even if each relationship is monogamous, your STD risk is increased.
Using alcohol or recreational drugs. These habits lower your inhibitions and impair your judgment, so you’re more likely to take sexual risks.
Injecting drugs. Needle-sharing spreads many dangerous infections, including HIV and hepatitis B. If you acquire HIV by injecting drugs, you can transmit it sexually.
Being young. Almost half of the new cases of STDs each year are in people between the ages of 15 and 24 years.
Being female. At all ages, women are more likely to have severe STD complications, such as infertility, than are men. In teenage girls and young adult women, the cervix is made up of constantly changing cells. These unstable cells make the cervix more vulnerable to certain sexually transmitted organisms, so vaginal intercourse poses added risks.
Being African-American. STDs, particularly gonorrhea and syphilis, are reported in a disproportionate number of African-Americans. This may be partly because African-Americans are more likely to receive care at clinics that report STD statistics, including breakdowns of cases by age, sex and race.
Having sex with men. Whether you’re male or female, male sex partners are riskier. For women, having vaginal intercourse or performing oral sex on a man without a latex condom is a high-risk activity. Homosexual men are also at increased risk of STDs, as are male and female sex workers and their customers. Some men who have heterosexual relationships also engage in clandestine sex with other men, posing risks to themselves and their partners of both sexes.
Meeting people in public places or online for sex. Casual, anonymous sex promotes the spread of STDs across social networks and different demographic groups.
Sexually transmitted diseases have a wide range of symptoms. The signs and symptoms listed here are the most common, but they occur in different combinations with different infections. The timelines from infection to symptoms — and from initial infection to advanced disease — also vary from disease to disease.
The first signs and symptoms of some STDs, occurring shortly after you’re exposed to a sexually transmissible agent, are known as primary or acute infection.
Primary infection symptoms
- May go unnoticed
- A sore or a cluster of sores or bumps, with or without pain, on the genitals or in the oral or rectal area
- Painful or burning urination
- Discharge from the penis
- Vaginal discharge
- Unusual vaginal bleeding
- Sore, swollen lymph nodes, particularly in the groin but sometimes more widespread
- Fever and other flu-like symptoms
- Appear a few days to three months after exposure, depending on the organism
- May be attributed to a noninfectious cause, such as a cold, fatigue or skin irritation
- May resolve in a few weeks, even without treatment, but progression with later complications — or recurrence — usually occurs (Transmission of some STDs may still be possible during this period.)
Advanced disease: Months to years after primary infection
- Sores or bumps anywhere on the body
- Recurrent genital sores
- Generalized skin rash
- Pain during intercourse
- Scrotal pain, redness and swelling
- Pelvic pain
- Groin abscess
- Infections associated with human immunodeficiency virus (HIV)
- For some infections, neurological or cardiovascular problems
When to see a doctor
See a doctor immediately if you are sexually active and you:
- Find out your sex partner has an STD
- Believe you may have been exposed to an STD
- Develop a genital sore or rash
- Have a discharge from the vagina or penis
- Have pain or a burning sensation when you urinate
- Have swollen or tender lymph nodes in your groin
Make an appointment with a doctor for STD counseling and, if appropriate, for screening tests:
- When you consider becoming sexually active, or when you’re 21, whichever comes first
- Before you start having sex with a new partner
- When you’re concerned about possible exposure to STDs in your past
Tests and diagnosis
If your sexual history and current signs and symptoms suggest that you have an STD, laboratory tests can identify the cause and detect co-infections you might also have contracted.
Blood tests confirm the diagnosis of most viral STDs. If you have active herpes sores, however, testing fluid and scrapings from the sores is simpler and less expensive than is testing blood.
Laboratory tests of material from a genital sore or discharge are used to diagnose the most common bacterial STDs at an early stage. Chlamydia may go unnoticed at this stage in both men and women, though, delaying the diagnosis until complications such as pelvic inflammatory disease (PID) occur. Women can easily miss the symptoms or signs of gonorrhea as well.
Antibiotics can cure many sexually transmitted bacterial and parasitic infections, including gonorrhea, syphilis, chlamydia and trichomonas. A single antibiotic dose, given orally or injected, is generally all you need to stop gonorrhea when it’s limited to the urethra and cervix. Typically, you’ll be treated for chlamydia at the same time because the two infections often appear together. Chlamydia treatment consists of a seven-day course of an oral antibiotic.
Once you start antibiotic treatment, it’s crucial to follow through. If you don’t think you’ll be able to take medication as prescribed, be sure to tell your doctor. A shorter, simpler treatment regimen may be available.
Sexually transmitted viral infections are not curable, but two such infections — human papillomavirus (HPV) and hepatitis B — are preventable with vaccines prior to exposure. You’ll have fewer herpes recurrences if you take daily suppressive therapy with a prescription antiviral drug, but you can still give your partner herpes at any time.
Treatment with highly active antiretroviral therapy and other antiviral drugs can keep HIV infection in check for many years, although the virus persists and can still be transmitted. The sooner you start treatment, the more effective it is. If you take anti-HIV medication for 28 days, starting as soon as you know you’ve been exposed, you may avoid becoming HIV-positive.
Vaccines are available to prevent two viral STDs that can cause cancer — human papillomavirus (HPV) and hepatitis B. The HPV vaccine is recommended for all girls between ages 9 and 26, and the hepatitis B vaccine is usually given to newborns.
Thanks to improved testing and treatment, most people with access to health care no longer face all the dreadful consequences of STDs. Still, there is no room for complacency. One risky encounter is unlikely to cost you your life, but it could really mess up your future. These guidelines offer the greatest possible margin of safety.
- Don’t have sex in any way that puts you and your partner in direct contact with each other’s blood, semen or other body fluids.
- Avoid vaginal and anal intercourse with new partners until you have both been tested for STDs. Oral sex is less risky, but use a latex condom or dental dam to prevent direct contact between the oral and genital mucosa.
- Use a latex condom every time you have intercourse.
- Never use an oil-based lubricant, such as petroleum jelly, with a latex condom.
- Don’t drink alcohol or use drugs. If you’re under the influence, you’re more likely to take sexual risks.
- Don’t look for sex partners online or in bars or other pickup places.
- Before any serious sexual contact, communicate with your partner about practicing safer sex. Reach an explicit agreement about what activities will and won’t be OK.
- Stay with one sex partner who doesn’t have any STDs and who won’t have sex with anyone but you.
Testing for a disease in someone who doesn’t have symptoms is called screening. Most of the time, STD screening is not a routine part of health care. But there are exceptions:
Everyone. The one STD screening test suggested for everyone between the ages of 13 and 65 is a blood or saliva test for human immunodeficiency virus (HIV), the virus that causes AIDS. Most health care settings in the United States offer a rapid HIV test with same-day results.
Pregnant women. Screening for HIV, hepatitis B, chlamydia, gonorrhea and syphilis generally takes place at the first prenatal visit. A blood test to detect HSV type 2 infection is recommended for pregnant women with current or past partners who have genital herpes.
Young women who are sexually active. All sexually active women under age 25 should be tested for chlamydia infection. The chlamydia test uses a sample of urine or vaginal fluid you can collect yourself. Some experts recommend repeating the chlamydia test three months after you’ve had a positive test and been treated. The second test is needed to confirm that the infection is cured, as reinfection by an untreated or undertreated partner is common. A bout of chlamydia doesn’t protect you from future exposures. You can catch the infection again and again, so you should get retested when you have a new partner.
Women ages 21 to 66. The Pap test screens for cervical abnormalities, including inflammation, precancerous changes and cancer, which is caused by certain strains of human papillomavirus (HPV). From ages 21 to 66, women should have a Pap test at least every three years. Women who start having sex before age 21 should have a Pap test within three years of first intercourse.
Men who have sex with men. Compared with other groups, men who have sex with men run a much higher risk of catching STDs. Many public health groups recommend annual or more frequent STD screening for these men. Regular tests for HIV, herpes, gonorrhea, chlamydia and syphilis are particularly important.