The mechanisms of HIV transmission

For HIV transmission to happen, four conditions need to be present:

  • Presence: Virus has to be present, first of all in the body of an infected person, and secondly in that person's body fluid or tissue to which another person is exposed.
  • Quantity: There has to be a sufficient amount of the virus in the body fluid through which the infection is conveyed. (Infectious virus may be present either as 'free' virus, or as viral DNA 'hidden' within infected cells: see In what form is HIV infectious?)
  • Route: Virus has to get into the body of the uninfected person through an effective route. 
  • Susceptibility: Finally, cells which are susceptible to infection must be present at the site of entry, and host defences must be inadequate to prevent infection.

We will follow the course of a potential new HIV infection by considering these factors one at a time.1,2


  1. Wu L Biology of HIV mucosal transmission. Curr Opin HIV AIDS 3(5): 534-540, 2008
  2. Gupta K et al. How do viral and host factors modulate the sexual transmission of HIV? Can transmission be blocked? PLoS Med 3(2): e79, 2006
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap