Efficiency of human immunodeficiency virus transmission through injections and other medical procedures: evidence, estimates, and unfinished business.

OBJECTIVE: To estimate the transmission efficiency of human immunodeficiency virus (HIV) through medical injections and other invasive procedures.
DESIGN: We searched our own files and Medline (from 1966-2004, using the keywords ["iatrogenic" or "nosocomial" or "injections"] and "HIV") for reports of iatrogenic outbreaks worldwide, except outbreaks traced to receipt of contaminated blood or blood products. We also analyzed information from a case-control study of percutaneous exposures to healthcare workers.
SETTING: Worldwide healthcare settings. EVENTS: We identified 8 iatrogenic outbreaks that met our study criteria; published information from 4 outbreaks was sufficient to estimate transmission efficiency.
RESULTS: From the 4 documented iatrogenic outbreaks, we estimated that 1 iatrogenic infection occurred after 8-52 procedures involving HIV-infected persons. Although only 0.3% of healthcare workers seroconvert after percutaneous exposure, a case-control study reported that deep injuries and other risk factors collectively increased seroconversion risk by as much as 50 times. Laboratory investigations demonstrate HIV survival through time and various rinsing regimens. We estimate that the transmission efficiency in medical settings with no or grossly insufficient efforts to clean equipment ranges from 0.5% to 3% for lower risk procedures (eg, intramuscular injections) and from 10% to 20% or more for high-risk procedures. Efforts to clean equipment, short of sterilization, may cut the transmission efficiency by 0%-100%. Procedures that contaminate multidose vials may accelerate transmission efficiency.
CONCLUSION: To achieve better estimates of the transmission efficiency for a range of medical procedures and settings, investigations of iatrogenic outbreaks should be accorded high priority.