Sources of evidence about HIV transmission

  • What we know about HIV transmission is based on different types of evidence.
  • Each type of evidence has strengths and weaknesses.
  • It's important to also apply common sense when looking at evidence of transmission risks.

Our picture of how HIV transmission can or cannot take place is based upon evidence and arguments drawn from many different sources. Broadly, these sources are:

  • Epidemiological evidence, or information drawn from observation of patterns of illness, infection and behaviour.
  • Virological evidence, or information drawn from the study of HIV and knowledge of other viral infections and the human immune system.
  • Risk analysis, or the likelihood of certain events happening given a specific combination of factors e.g. infection of patients by surgeons compared with other risks.

However, not all pieces of evidence are of equal weight, of equally valid methodology, or of equal accuracy. The complete picture of risk assessment depends upon using all these methods together in combination. On its own, evidence drawn from any one discipline can lead to the wrong conclusions. For example, if one were to take virological evidence alone, kissing would seem to be a plausible route of transmission because of the isolation of HIV in saliva. Yet epidemiological evidence consistently fails to show kissing to be a risk for HIV infection.

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 It may have been superseded by more recent developments.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.