Based on the detection of HIV RNA in syringes recently used in HIV-infected patients Apetrei and colleagues [1] claimed that they ‘provided proof of concept that injection practices could account for a significant proportion of new HIV infections’. This is used to counter the conclusions of epidemiological studies from rural Zimbabwe and Uganda, where no association of HIV infection and a self-reported history of injections was found [2,3]. Debate about the role of unsafe injections in the HIV epidemics of sub-Saharan Africa is not about the potential of HIV transmission through injection with contaminated needles but the proportion of infections acquired through this route [4,5]. We agree that ‘the belief that HIV may not be transmitted by re-used needles is dangerous to public health’ [1], but no one has argued that HIV cannot be transmitted in this way.
Through sensitive reverse transcriptase–polymerase chain reaction, HIV-related genetic material could be detected in approximately one in three syringes used for intravenous injections and one in 40 syringes used for intramuscular injections [1], clearly showing some contamination of syringes. However, no evidence is given to support their conclusion of the important role of injections in the epidemic because the study offered no insights into injection practices. HIV-contaminated needles may have many alternative fates: only a fraction will be re-used [6], and if they are they may be sterilized or flushed. Even if re-used unsterilized, the probability of transmission per needle stick has been estimated to be between 0.24% (the risk of accidental needle sticks) and 0.65% (the risk of intravenous illicit drug use) [7]. Modelling work has indicated that, with the highest of these transmission probabilities, an annual average in excess of five unsafe injections per person would be required to generate an HIV epidemic [8]. Furthermore, the majority of injections administered in sub-Saharan Africa are intramuscular [5], which, as observed by Apetrei et al. [1], are much less likely to be contaminated.
In this debate, the issue is not ultimately whether virus can be detected, but whether exposure is occurring and causing new infections. To answer this, observational epidemiological data will remain key; and the increasing evidence from the field, analysed directly [2,3] and to inform models [8], does not support a major role for unsafe injections in the HIV epidemics in Africa.
Conflict of Interest: GPG has acted as a consultant for and/or received grants from GlaxoSmithKline, Aventis Pasteur, Merck, and Abbott Pharmaceuticals. GPG also chaired a meeting of the World Health Organization in 2003 to develop a consensus on the importance of unsafe injections in HIV epidemiology. SG owns shares in GlaxoSmithKlineBeecham and Astra Zaneca.
References
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et al. The incidence of HIV-1 associated with injections and transfusions in a prospective cohort, Rakai, Uganda. AIDS 2004; 18:342–344.
3. Lopman BA, Garnett GP, Mason PR, Gregson S. Individual level injection history: a lack of association with HIV incidence in rural Zimbabwe. PLoS Med 2005; 2:e37.
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