Men’s health centre

Understanding STIs - the basics

What are STIs?

STIs are sexually transmitted infections. They are sometimes referred to as sexually transmitted diseases or STDs. This means they are most often - but not exclusively - spread by sexual intercourse. HIV, chlamydia, genital herpes, genital warts, gonorrhoea, syphilis, trichomoniasis and some forms of hepatitis are all STIs.

STIs used to be called venereal diseases or VD. They are among the most common contagious diseases.

According to the Health Protection Agency (HPA), in 2009 there was a 3% increase from the previous year (2008) in the number of new diagnosed STIs, with a total of 482,696 new cases. According to the HPA, chlamydia is the most commonly diagnosed STI in the UK with 217,570 cases diagnosed in 2009 - up 7% from 203,773 in 2008. STIs are serious illnesses that require treatment. Some STIs, such as HIV, cannot be cured and can be fatal. By learning more about STIs, you can find out ways to protect yourself.

You can get an STI by vaginal, anal or oral sex. You are at high risk if:

• You have more than one sex partner.
• You have sex with someone who has had many partners.
• You don't use a condom when having sex.
• You share needles when injecting intravenous drugs.
• You trade sex for money or drugs.

Sexually transmitted infections can be cured or managed if they are treated early. You may not realise you have an STI until it has damaged your reproductive organs (which could leave you with difficulties falling pregnant), your vision, your heart or other organs. Having an STI weakens the immune system and leaves you more vulnerable to other infections. Pelvic inflammatory disease (PID) is a complication of many STIs that can affect a woman’s fertility. If you pass an STI to your newborn child, the baby may suffer permanent harm.

What causes STIs?

Bacterial STIs include chlamydia, gonorrhoea and syphilis. Viral STIs include HIV, genital herpes, genital warts (HPV) and hepatitis B. Trichomoniasis is caused by a parasite.

The germs that cause STIs hide in semen, blood, vaginal secretions, and sometimes saliva. Most of the organisms are spread by vaginal, anal, or oral sex, but some, such as those that cause genital herpes and genital warts, may be spread through skin contact. You can get hepatitis B by sharing personal items, such as toothbrushes or razors, with someone who has it.