These are conditions usually caused by infections that can affect the genital area and urinary system.

Some infections are caught from another person, usually during sex.
Other cases are caused when organisms (bacteria or yeast), which are usually present in small numbers, overgrow and cause symptoms.
Some genitourinary (GU) diseases are caused by bacteria that do not cause problems in their usual home in the body, but do if they get into another place.

These diseases are often managed best at a genitourinary medicine (GUM) or sexual health clinic.

Young people are at greatest risk of sexually transmitted infections.

They are very unlikely to have been exposed to any sexually transmitted infections before they start having sex, so they have no chance to build up immunity (when the body can fight off an infection by itself).
In young women, the cervix (neck of the womb) is immature and is easier to infect. In general, women are more likely to be infected by a man than vice versa.
Younger people may have more partners or change partners more frequently than older generations. Sexual behaviour is the most important influence on whether you get a sexually transmitted infection. If you have sex with someone who is infected then you are likely to get the infection yourself. The more partners you have the more likely you are to have sex with someone who is infected.