2.1 Behavioural data serves as an early warning system for HIV and STDs

Behavioural risk is not distributed uniformly throughout a population. On average, some subpopulations or communities may have higher levels of risk behaviour than others. Which subpopulations or communities are particularly vulnerable can vary greatly from country to country and may need to be defined locally in terms of occupation, migration status, sexual orientation, geographic location, income level, or any number of other factors. Behavioural data can help identify those subpopulations or communities at risk locally and can suggest the pathways the virus might follow if nothing is done to brake its spread. It can also indicate the levels of risk behaviour in the general population and the behavioural "bridges" between the general population and more vulnerable subpopulations. If these "bridges" are strong, arresting HIV transmission in vulnerable subpopulations or communities early becomes an urgent and critical component of slowing the spread in the population as a whole.

This kind of behavioural information can act as a call to arms for many people - politicians, religious and community leaders, and people who may themselves be at risk - signalling that the threat of HIV is very real even in areas where it is not yet visible. Such data are a powerful tool in pressing for action.