Several factors are important in determining if the HIV virus can be passed from an infected person to another one. These include biological and social factors which both relate to the exposed and the infectious individuals.
This conceptual framework summarises only the biological factors that influence HIV transmission. When assessing the risk of infection, each should be considered in turn and as a whole.
Exposure alone is not enough to predict the risk of infection, viral load matters and though there is no direct correlation between viral load and infectiousness, a high viral load has been associated with higher infectiousness. However, a low viral load may not be underrated if exposure is direct through blood, like with IDUs.
When it comes to sex with an HIV-infected person or a person of unknown status, different levels of risk have been attributed to different sexual practices. But this does not mean that the risk is always the same for the same practice. Oral sex may be overall much safer than unprotected anal sex, but oral sex with bleeding teeth and rotten gum isn’t certainly safe!
By and large, there is no clear cut or definitive risk factor and often risk is what we estimate it to be and how we relativise it. The risk of HIV infection is dynamic and depends on many factors who weight differently. Though there is an agreement that some factors weight more than other this cartoon does not give a weight to each factor identified as this is open to debate and only add to the existing confusion around risk.
Knowing and understanding what these factors are and how they interact one with another to determine the overall level of risk of HIV infection when exposed to the virus, particularly during sexual intercourse, will help individual to assess the risk of being infected.