Bridging - Understanding HIV Transmission Dynamics

What is Bridging?

Bridging, literally ‘making the bridge’, is a key concept for understanding HIV transmission dynamics. It has no direct and established French equivalent, so the English term is used. Bridging describes the behavior of an HIV-negative person who has unprotected sex with both HIV-positive and HIV-negative partners.

The Bridge Between Communities: Transmission Mechanism

Imagine two groups of people who primarily have sexual relations with each other: a group of HIV-positive people and a group of HIV-negative people. The ‘bridge’ is an HIV-negative person who is part of both sexual networks. By having unprotected sex with an HIV-positive person, this person risks contracting HIV. If infected and not yet aware (during the primary infection phase where viremia is very high), they can then transmit the virus to their HIV-negative partners.

This person acts as a bridge, allowing the virus to pass from one group to another. It is an essential link in the chain of HIV transmission, explaining how the virus can continue to spread even in communities where people think they are taking precautions by choosing partners of the same serological status.

Serosorting and Reality: The Limits

Bridging highlights the limitations of ‘serosorting’ (the act of choosing partners based on their HIV status). Many people believe they are safe by only sleeping with HIV-negative individuals. But this strategy relies on blind trust and a perfect, up-to-date knowledge of everyone’s status, which is unrealistic. A person may have been recently infected and not yet know it, or lie about their status.

Bridging shows that sexual networks are much more interconnected than one might think. You may feel like you’re staying in a ‘safe’ circle, that there’s a gay community that doesn’t meet curious heterosexuals who are more likely to go with bisexuals, but one of your partners could be a bridge to another at-risk circle. This is why strategies like condoms, PrEP, and regular testing are so important: they don’t depend on your partner’s status or honesty, but on your own actions to protect yourself.