- have received a positive Chlamydia or gonorrhoea test result or have been diagnosed with NSU in the last 2 weeks
- OR have started treatment for Chlamydia, gonorrhoea, or NSU in the last 2 weeks
- own a personal mobile phone
- be aged 16 to 24 (according to clinic data)
- be able to provide informed consent (patients who lack mental capacity and those unable to understand English will not be recruited)
- known to be a sexual partner of someone already recruited to the trial.