Many genital and urinary tract infections are spread though close physical contact with an infected person. Unprotected sex is therefore the most common way of passing on the infection. Sexually transmitted diseases (STDs) include the following:

• chlamydia,
• gonorrhea,
• HIV and AIDS,
• hepatitis,
• genital herpes,
• syphilis, and
• trichomonas vaginalis (TV).

Sometimes, infections of the genitals and urinary tract are caused by other things. Thrush, bacterial vaginosis, and genital warts are examples of infections that can be caught or transmitted in ways other than unprotected sex. Women can also get infections by forgetting to remove tampons.

• Thrush is a common infection in women that happens when the naturally occurring fungus, candida albicans, grows excessively. This may be caused by pregnancy, menstruation, diabetes, taking the pill, wearing tight underwear and taking antibiotics. It can sometimes develop following sex with an infected person, but this is uncommon.
• Bacterial vaginosis (BV) is the most common cause of vaginal discharge. If it isn't treated, it can cause miscarriage, premature labor and pelvic inflammatory disease (PID). It isn't clear if BV is caused by unprotected sex, but it may be linked to having a lot of sexual partners. It can also be triggered by the IUD contraceptive (previously called the coil).
• Genital warts are small, round lumps on and around the genitals. They are caused by the human papilloma virus (HPV), which is passed by close skin-to-skin contact.
• Scabies is a skin infection that is passed on through close physical contact with an infected person. This may be through sex, but occasionally it can also be passed on through towels and bedding.
• Non-specific urethritis is an infection of the urethra (the tube where urine comes out) that only affects men. It's usually caused by having sex with a partner who already has an STD. However, it is also caused by other genital or urinary tract infections, damage to the urethra through vigorous sex or masturbation, or urine and bladder infections (although bladder infections are rare in young men).
• Cystitis is a common bladder infection in women. Infection enters the urinary tubes as a result of poor hygiene or sex. Stress, bad diet, dehydration, oral contraceptives and antibiotics can also trigger it.

Remember that anyone who has sex, including oral sex and anal sex, or close genital-to-genital contact with an infected person, can catch an STD.