Abstract
The transmission efficiency of HIV-1 through unsafe medical injections can be estimated from seroconversions among health care workers (HCWs) after percutaneous exposures and documented iatrogenic outbreaks. Data from a case-control study of seroconversion after percutaneous exposures among US and European HCWs shows an average rate of seroconversion after deep injuries - arguably comparable to unsafe injections - of 2.3%. Information from an iatrogenic HIV outbreak in a Romanian orphanage suggests a transmission efficiency of 2-7%. Even these estimates may be too low to explain the rapid spread of HIV among Russian and Libyan children in iatrogenic outbreaks discovered in 1988 and 1998, respectively. In countries in sub-Saharan Africa and elsewhere with high HIV prevalence and large numbers of unsafe injections, personal risk as well as the share of the HIV epidemic associated with unsafe injections may be an order of magnitude higher that many experts have supposed.