Sexually transmitted infections (STIs) are usually spread by people having sex without a condom, or sometimes simply through touching the genital area of an infected person. The most common are:
Chlamydia: Symptoms include pain while urinating, unusual discharge from the genitals. Women may bleed after sex or between their usual monthly cycles.
However, many people who contract this infection do not show any symptoms and so may not realise they have it. Chlamydia can be treated with antibiotics, but if ignored, it can spread and cause infertility or other long-term health problems.
Syphilis: Syphilis manifests itself in stages. The first stage causes an infectious sore to appear near the mouth or genitals, which, although painless, can easily spread to other people in the two to six weeks it takes to clear up.
The second stage develops next with non-itchy skin rashes, headaches and sore throats, and once these disappear, there may be no outward symptoms as it enters the ‘latent’ phase.
However, carriers are still infectious during this period, which could last years, and if it goes untreated and reaches the dangerous tertiary phase, syphilis can spread to the organs, raising the risk of stroke and other serious health conditions, even death. Syphilis can be treated with penicillin.
Gonorrhoea: Like chlamydia, symptoms of this bacterial infection include painful urination and unusual genital discharge for men and women, but often people with it show no outward signs.
Historically known as ‘the clap’, gonorrhoea is relatively easy to treat with antibiotics.
Genital herpes: This incurable condition is caused by the herpes simplex virus (HSV), which remains inactive most of the time with occasional outbreaks of painful blisters around the genitals.
It can be controlled using antiviral medicines but is highly contagious and usually transmitted through unprotected sex. As there are often no symptoms, many people are unaware they are infected.
Genital warts: These unsightly, painless growths are caused by a viral skin infection that comes from the human papillomavirus (HPV), which has also been linked to cervical cancer.
HPV is spread by skin contact so full sex is not needed to catch genital warts, but it may take up to a year for the small bumps to appear.
They pose a relatively small health risk and are treated with creams or may be frozen.