STIs, or sexually transmitted infections, are a group of illnesses which can be passed from person to person during unprotected sex, or if genitals come into contact. Most can be diagnosed using a urine or blood test. Chlamydia is the most common STI and can be reasonably harmless, as long as it is treated early. HIV, on the other hand, is incurable and will affect a sufferer for life.
Symptoms can vary depending on the STI contracted, and some infections actually do not display symptoms. Most people with chlamydia, for example, don’t experience any ill effects, and 50% of women suffering from gonorrhoea aren’t aware they are infected with it. The best way to prevent STIs is to always use a condom during sex, and to have regular check ups to ensure any infections are caught as soon as possible.