A person with an STI can pass it to others by contact with skin, genitals, mouth, rectum, or body fluids. Anyone who has sexual contact—vaginal, anal, or oral sex—with another person may get an STI. STIs may not cause symptoms. Even if there are no symptoms, your health can be affected.

STIs are caused by bacterial or viral infections. Sexually transmitted infections caused by bacteria are treated with antibiotics. Those caused by viruses cannot be cured, but symptoms can be treated.

The following factors increase the risk of getting STIs:

• More than one sexual partner
• A partner who has or has had more than one sexual partner
• Sex with someone who has an STI
• History of STIs
• Use of intravenous drugs (injected into a vein) or partner use of intravenous drugs. Adolescents have a higher risk of getting an STI than adults

• Chlamydia (see FAQ071 “Gonorrhea, Chlamydia, and Syphilis”)
• Gonorrhea (see FAQ071 “Gonorrhea, Chlamydia, and Syphilis”)
• Genital herpes (see FAQ054 “Genital Herpes”)
• Human immunodeficiency virus (HIV) infection (see PFS005 “Testing for Human Immunodeficiency Virus”)
• Human papillomavirus (HPV) infection (see FAQ191 “Human Papillomavirus [HPV] Vaccination”)
• Syphilis (see FAQ071 “Gonorrhea, Chlamydia, and Syphilis”)
• Trichomoniasis (see FAQ028 “Vaginitis”)
• Hepatitis B (see FAQ125 “Protecting Yourself Against Hepatitis B and Hepatitis C”)

There are many ways you can reduce your risk of getting an STI:

• Know your sexual partners and limit their number—Your partner’s sexual history is as important as your own. The more partners you or your partners have, the higher your risk of getting an STI
• Use a latex condom—Using a latex condom every time you have vaginal, oral, or anal sex decreases the chances of infection. Condoms lubricated with spermicides do not offer extra protection. Frequent use of some spermicides can increase the risk of HIV
• Avoid risky sex practices—Sexual acts that tear or break the skin carry a higher risk of STIs. Even small cuts that do not bleed let germs pass back and forth. Anal sex poses a high risk because tissues in the rectum tear easily. Body fluids also can carry STIs. Having any unprotected sexual contact with an infected person poses a high risk of getting an STI
• Get immunized—Vaccinations are available that will help prevent hepatitis B and some types of HPV (see FAQ191 “Human Papillomavirus [HPV] Vaccination” and FAQ125 “Protecting Yourself Against Hepatitis B and Hepatitis C”)

Having an STI during pregnancy can harm the baby. Gonorrhea and chlamydia both can cause health problems in the infant ranging from eye infections to pneumonia. Syphilis may cause miscarriage or stillbirth. Human immunodeficiency virus infection can occur in a baby.

If you are pregnant and you or your partner have had—or may have—an STI, inform your health care provider. Your baby may be at risk. Tests for some STIs are offered routinely during prenatal care. It is best to treat the STI early to decrease the chances that your baby also will contract the infection. You and your partner both may have to be treated.

Gonorrhea, chlamydia, and syphilis are sexually transmitted infections (STIs). These three STIs can cause serious, long- term problems if they are not treated, especially for teenagers and young women.

Both gonorrhea and chlamydia are caused by bacteria. The bacteria are passed from one person to another through vaginal, anal, or oral sex. Gonorrhea and chlamydia often occur together.

Gonorrhea and chlamydia infections can occur in the mouth, reproductive organs, urethra, and rectum. In women, the most common place is the cervix (the opening of the uterus).

Although gonorrhea and chlamydia can occur at any age, young women and teenagers who are sexually active are at greater risk of both infections.

Women with gonorrhea or chlamydia often have no symptoms. When symptoms from either infection do occur, they may show up 2 days to 3 weeks after infection. They may be very mild and can be mistaken for a urinary tract or vaginal infection.

The most common symptoms in women include the following:

• A yellow vaginal discharge
• Painful or frequent urination
• Vaginal bleeding between menstrual periods
• Rectal bleeding, discharge, or pain

To find out if you have gonorrhea or chlamydia, your health care professional may take a sample of cells from your throat, cervix, urethra, or rectum where the infection may occur. Gonorrhea and chlamydia also can be detected with a urine test.

Both gonorrhea and chlamydia can cause pelvic inflammatory disease (PID), an infection that occurs when bacteria move from the vagina and cervix upward into the uterus, ovaries, or fallopian tubes. After a woman is infected with gonorrhea or chlamydia and if she does not receive treatment, it can take anywhere from a few days to a few weeks before she develops PID.

Gonorrhea and chlamydia are treated with antibiotics. You will need to be retested 3 months after treatment to see if the infection is gone.

Syphilis also is caused by bacteria. It differs from gonorrhea and chlamydia because it occurs in stages. It is spread more easily in some stages than in others.

The bacteria that cause syphilis enter the body through a cut in the skin or through contact with a syphilis sore known as a chancre. Because this sore commonly occurs on the vulva, vagina, anus, or penis, syphilis most often is spread through sexual contact. It also can be spread by touching the rash, warts, or infected blood during the secondary stage of infection.

Symptoms of syphilis differ by stage:

• Primary stage - Syphilis first appears as a painless chancre. This sore goes away without treatment in 3–6 weeks.
• Secondary stage - The next stage begins as the chancre is healing or several weeks after the chancre has disappeared, when a rash may appear. The rash usually appears on the soles of the feet and palms of the hands. Flat warts may be seen on the vulva. During this stage, there may be flu-like symptoms. This stage is highly contagious.
• Latent and late stages - The rash and other symptoms go away in a few weeks or months, but the disease still is present in the body. If untreated, the disease may return in its most serious form years later.

In the early stages, discharge from open sores is examined to see if syphilis bacteria are present. In later stages, a blood test also can be done to check for antibodies to the bacteria.

Late-stage syphilis is a serious illness. Heart problems, neurologic problems, and tumors may occur, leading to brain damage, blindness, paralysis, and even death. The genital sores caused by syphilis also make it easier to become infected with and transmit human immunodeficiency virus (HIV).

Syphilis is treated with antibiotics. If it is caught and treated early, long-term problems can be prevented. The length of treatment depends on how long a person has had the disease.

You can take steps to avoid getting gonorrhea, chlamydia, or syphilis. These safeguards also help protect against other STIs:

• Use a condom. Both male and female condoms are sold over the counter in drug stores. They help protect against STIs.
• Limit your sexual partners. The more sexual partners you have over a lifetime, the higher your risk of getting STIs.
• Know your partner. Ask about your partner’s sexual history. Ask whether he or she has had STIs. Even if your partner has no symptoms, he or she still may be infected.
• Avoid contact with any sores on the genitals.

STDs are caused by bacterial or viral infections through sexual contact via genitals, anal, mouth or body fluids.

1. Bacterial : 
   - Gonorrhoea
   - Chlamydia
   - Trichomonas
2. Viral
   - Herpes
   - HIV
   - HPV
   - Hepatitis B and C

• Stick to one partner who equally should do the same
• Use condoms
• Have vaccination and immunity