The concept is as follows:

1. Individuals, who wish to, would be given anonymous health status cards - cards carrying a photo and a 16-digit number and no further identifying details.
2. These individuals, if they wish, would be tested for a number of sexually-transmitted infections - including HIV.
3. These test results would be placed in a database accessible by a number of means (telephone, web, cell, SMS and etc.)
4. To access the data, the individual would need to give the number on the anonymous card and the associated PIN - just like with banking cards.
5. This individual would be able to share his/her longitudinal data with any other individual he/she wishes to. This other person would be able to reciprocate.
6. Each person can decide, depending on the information available, whether to have sex or not. They can even decide on what sort of sex to have.

The objective of this concept:

1. To eliminate high-risk individuals from a risky relationship with the card-holder.
2. To limit the card-holder's relationships to low-risk individuals.
3. To allow infected individuals to have sex with others provided these people are aware of their health-status.

Disease-transmission is dependent on highly-promiscuous individuals who connect together disparate clusters of individuals - where each cluster encompasses a social grouping of people with similar interests or backgrounds.

Scale-free networks are resilient to random failure but are highly susceptible to the destruction of the best-connected nodes - see Nature article.