Sexually transmitted diseases, now more commonly known as sexually transmitted infections, are infections that are spread through sexual contact and unprotected sexual intercourse. Sexually transmitted infections can be passed on through oral, anal and vaginal sex. Some infections, including genital warts, can also be passed through skin to skin contact. How common are sexually transmitted infections? Sexually transmitted infections are very common. In recent years, the number of people diagnosed with an STI has increased significantly. The figure has increased year on year since the mid 1990’s and in 2008 a total of 399,738 new cases were diagnosed. Chlamydia is the most commonly diagnosed sexually transmitted infection in the UK but there has been a significant increase in the number of cases of genital herpes; between 2007 and 2008 there was a 10 percent increase in the number of cases. Young people aged between 16 and 24 are the most commonly affected. This demographic acco