Perimeter migrant(s) are previously interviewed / enrolled individual(s) during earlier study round who move(s) to an area within 200 metres from the study community (or DSS site) boundary. The coding on the mobility / migration form should indicate from where they moved plus the information that it is a perimeter migrant. In certain sites, such individuals are of interest to follow up in cohort work as they continue to be linked to the networks with whom they were originally identified.