Chlamydia is a very common sexually transmitted infection (STI) and one of the most serious. It can spread silently in men and women and cause infertility. There often aren't any symptoms.

Cystitis is an infection of the bladder causing burning sensations during urination.

Genital herpes causes painful sores on and around the genitals. It is spread by direct contact with sores during sex, but can also be passed when no sores are present. There is no known cure.

Genital warts are one of the most common sexually transmitted infections.

Gonorrhoea is a common sexually transmitted infection (STI), also known as 'the clap'. If not treated early, it can cause serious health problems.

Hepatitis A & C is inflammation of the liver. This can be caused by alcohol and some drugs, but usually it is the result of a viral infection. There are several viruses which can cause hepatitis.

Hepatitis B (HBV) is an infection of the liver caused by a virus. It's much easier to get than HIV, and can cause permanent liver disease and cancer. Most people have no obvious symptoms, and there is no known cure.

HIV stands for Human Immunodeficiency Virus and is a virus that can damage the body's defence system so that it cannot fight off certain infections.

Non-specific urethritis (NSU) is usually caused by a sexual infection. NSU only affects men.

Syphilis is a bacterial infection and can be spread without either partner knowing. The first signs are painless sores, followed by flu-like symptoms. Left untreated, it can lead to heart disease or brain damage.

Trichomoniasis, (sometimes called TV), can infect both men and women but many people who are infected have no symptoms.

If you want more information call the Sexual Health Line free (from the UK) T: 0800 567 123 or phone your local NHS sexual health clinic.