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Programme Science
Distinguishing sources of HIV transmission from the distribution of newly acquired HIV infections: why is it important for HIV prevention planning?
  1. Sharmistha Mishra1,
  2. Michael Pickles1,
  3. James F Blanchard2,
  4. Stephen Moses2,
  5. Marie-Claude Boily1
  1. 1Department of Infectious Disease Epidemiology, Imperial College London, London, UK
  2. 2Centre for Global Public Health, University of Manitoba, Winnipeg, Canada
  1. Correspondence to Dr Sharmistha Mishra, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College, St. Mary's Campus, Norfolk Place, Praed Street, London W2 1NY, UK; sharmistha.mishra08{at}


Objective The term ‘source of HIV infections’ has been referred to as the source of HIV transmission. It has also been interpreted as the distribution of newly acquired HIV infections across subgroups. We illustrate the importance of distinguishing the two interpretations for HIV prevention planning.

Methods We used a dynamical model of heterosexual HIV transmission to simulate three HIV epidemics, and estimated the sources of HIV transmission (cumulative population attributable fraction) and the single-year distribution of new HIV infections. We focused an intervention guided by the largest transmission source versus the largest single-year distribution of new HIV infections, and compared the fraction of discounted HIV infections averted over 30 years.

Results The single-year distribution of newly acquired HIV infections underestimated the source of HIV transmission in the long term, when the source was unprotected sex in high-risk groups. Under equivalent and finite resources, an intervention strategy directed by the long-term transmission source was shown to achieve a greater impact than a distribution-directed strategy, particularly in the long term.

Conclusions Impact of HIV prevention strategies may vary depending on whether they are directed by the long-term transmission source or by the distribution of new HIV infections. Caution is required when interpreting the ‘source of HIV infections’ to avoid misusing the distribution of new HIV infections in HIV prevention planning.

  • Transmission Dynamics
  • Programme Science
  • Modes of Transmission
  • Mathematical Model
  • HIV

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