An individual's relationships and the groups (including family), to which they belong can have a significant impact on his or her health. Health communication programmes can work to shape the information a group receives and may attempt to change communication patterns within the group. Opinion leaders within a network are often a point of entry for health programmes such as family-based HIV counselling and testing, or peer education. Targeting health communication at social networks may result in a diffusion of innovations and network-based health strategies. It can also provide opportunities for voluntary counselling and health tests for all network members.