Many STIs can be asymptomatic, which means people can be carriers and pass the infection onto other people without realising. For this reason, it is sensible to practise safer sex methods, particularly using condoms for vaginal, anal and oral sex, especially with new partners.

Chlamydia

Is the one of the most common STIs in the UK, with particularly high prevalence in younger adults. It is a bacterial infection that affects the cervix or urethra and can spread to other areas such as the uterus or fallopian tubes. The majority of people with chlamydia have no symptoms at all and, for this reason, all 15- to 24-year-olds who are sexually active are recommended to have a chlamydia test each year. The infection is usually straightforward to treat with antibiotics and it is important to do so in order to avoid complications such as fertility problems and pelvic inflammatory disease (see next slide).

Gonorrhoea

Gonorrhoea is another bacterial STI that is often asymptomatic. It most commonly affects the urethra, cervix or rectum, and sometimes the throat. Again, it is easily treated with antibiotics; failure to do so can lead to serious long-term problems such as reduced fertility, pelvic inflammatory disease and some forms of arthritis.

Genital warts

Are caused by a virus and manifest as bumps or lumps – they may be large or small, and smooth or uneven – on any part of the vagina, penis or anus. The warts can be painful or feel itchy, but even if they aren’t causing any problems or the individual has been treated, the virus can be transmitted to other people. The warts often disappear without treatment, but chemical products or cryotherapy (freezing treatment) may be used to try and get rid of them if they are unsightly – though success rates are variable.

Genital herpes

Is another viral infection. Sufferers may experience burning or tingling in their vagina, penis or anus, and develop fluid-filled blisters and a fever. However, the infection can also be symptom-free. There is no treatment, though antiviral medication can help clear up the blisters more quickly and prevent more attacks.

Pubic lice

Are tiny insects that live in coarse body hair, such as that around the genitals. They are sometimes known as crabs and, although different to head lice, the treatment is similar: insecticide products.

Syphilis

Is not as common as some other STIs, but it can be very serious if left untreated. There are three phases to the infection:

1. The first starts within three months of contracting the bacteria when one or more painless sores appear, most commonly on the penis, anus, vagina, cervix or mouth, before healing after a few weeks
2. Phase two begins shortly after the sores have healed and usually involves a rash and flu-like symptoms
3. The tertiary phase can develop many years later if the infection is not treated with antibiotics before this stage, and can affect many parts of the body including the nervous system and heart.