Each study subjects will be offered either an interactive WhatsApp reminder to return to the centre for taking faecal tubes for screening; or usual care, where no additional intervention will be offered. A simple random sampling process will be administered using computer-generated numbers so that each participant will have a 50% probability for assignment into each group. All potential participants identified who are eligible for the study will be randomized by a computer randomizer, which will give a number indicating the group assigned.