Lancet article destroys the thesis that injections a major cause of HIV in Africa

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There is no compelling evidence that unsafe injecting practices are responsible for the bulk of HIV infections in southern Africa, a team of investigators conclude in an article in the February 7th edition of The Lancet.

The investigators, from internationally respected bodies including the World Health Organisation, UNAIDS, the US Centers for Disease Control, and the London School of Hygiene and Tropical Medicine conducted their review after US researchers (Guisselquist et al) suggested in early 2003 that the importance of unsafe injecting practices in the spread of HIV in southern Africa had been gravely under-estimated, and that rather than causing under 3% of infections, contaminated injecting equipment caused as many as 40% of HIV infections.

Suggestions that sexual transmission of HIV might not be as important as previously thought prompted hearings in the US Senate to see whether prevention resources should be diverted from safer sex programmes to safer medical injecting initiatives.



The study of the causes of a disease, its distribution within a population, and measures for control and prevention. Epidemiology focuses on groups rather than individuals.

herpes simplex virus (HSV)

A viral infection which may cause sores around the mouth or genitals.


The Joint United Nations Programme on HIV/AIDS (UNAIDS) brings together the resources of ten United Nations organisations in response to HIV and AIDS.


Injected into a muscle.


Confounding exists if the true association between one factor (Factor A) and an outcome is obscured because there is a second factor (Factor B) which is associated with both Factor A and the outcome. Confounding is often a problem in observational studies when the characteristics of people in one group differ from the characteristics of people in another group. When confounding factors are known they can be measured and controlled for (see ‘multivariable analysis’), but some confounding factors are likely to be unknown or unmeasured. This can lead to biased results. Confounding is not usually a problem in randomised controlled trials. 

The article in The Lancet examined the case that contaminated medical equipment causes a substantial number of HIV infections, and rebutted it, point by point. The authors concluded that that there is “no compelling evidence that unsafe injections are the dominant mode of HIV-1 transmission in sub-Saharan Africa.” The authors reviewed existing research on injecting practices and the epidemiology of HIV and sexually transmitted infections in Africa.

There were five main components of Guisselquist’s thesis:

Point 1: Unsafe injections are common

Only 18% of injections in sub-Saharan Africa are carried out using non-sterile injecting equipment, argue the authors, considerably less than the 50% suggested by Guisselquist. Further, the frequency with which individuals receive potentially unsafe injections is considerably lower than that estimated by Guisselquist.

The Lancet article also reported evidence that the majority of injections were intramuscular, involving little contamination with blood. Indeed, testing of used injecting equipment revealed that only 5% was contaminated with a potentially infectious amount of HIV, and that as healthcare workers usually washed or rinsed needles and syringes prior to reuse, this would further reduce the potential for contaminated equipment to carry infectious amounts of HIV.

Point 2: Transmission efficiency via unsafe injections

Guisselquist maintained that contaminated injections are an efficient way of transmitting HIV, with a risk rate of 2.3%. However, evidence from healthcare workers suggests an average risk rate of 0.2%. This risk would be reduced even further by efforts made by African healthcare workers to clean injecting equipment.

Point 3: Population factors

Guisselquist argued that there was a strong association between a history of injections and HIV infection amongst sub-Saharan Africans. However, he did not take into account confounding factors, such as sexual history, or a history of sexually transmitted infections.

Point 4: Age and sex patterns of infection

Guisselquist maintained that there was a high rate of HIV infections in individuals who were unlikely to have ever had sex, for example children. However, six population-based studies provided evidence to the Lancet authors of extremely low rates of HIV infection in children and adolescents (0% - 10%), with no evidence that infection was from any route other than mother-to-baby transmission.

Point 5: Sex as the primary mode of HIV transmission

There is only a weak association between sexual behaviour and HIV rates in southern Africa, Guisselquist argued. Yet the epidemiology of herpes simplex virus-2 (HSV-2), which causes genital ulcers and is a recognised risk factor for HIV, closely mirrors that of HIV in sub-Saharan Africa, following an age and sex pattern similar to HIV.

In addition, South Africa has developed an HIV epidemic of massive proportions, despite having high standards of hygiene and infection control in its healthcare facilities.

The authors in The Lancet conclude that “epidemiological evidence indicates that sexual transmission continues to be the major mode of spread of HIV-1 in Africa”, but call for additional measures to reduce exposure to blood-borne infections through unsafe injecting practices.

Further information on this website

Sex, not injections, drives HIV epidemic in Zimbabwe - news story

AIDS in Africa: WHO & UNAIDS reaffirm unsafe sex as main mode of transmission - news story


Schmid GP et al. Transmission of HIV-1 infection in sub-Saharan Africa and the effect of elimination of unsafe injections. The Lancet 363: 482 – 488, 2004.