What Is the Risk of Getting HIV From a Needlestick Injury?

CDC Study Highlights the Differences in Perceived and Actual Risk

Taking Blood

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Needlestick injuries—as well as any percutaneous injury that can expose a person to tainted blood or body fluids—have long been a concern to both healthcare workers and the public at large.

Many of the fears have been fueled by media reports which either overstate the risk of acquiring HIV through needlestick injuries or spotlight cases in which victims are reported to be "living in fear" after having received such exposure (including much-reported incident in 2013 where a Michigan woman sued Etihad Airways after puncturing herself on discarded hypodermic needle left in a seatback pocket).

While the perception of risk may be high in cases of needlestick injuries, recent analyses from the Centers of Disease Control and Prevention (CDC) suggests that the actual risk may be far lower—so low, in fact, that it can now be considered rare.

Questioning the "Three Out of a Thousand" Estimate

In a popularly referenced 1989 study, researchers suggested that the risk of acquiring HIV from a single needlestick injury involving HIV-contaminated blood was around 0.32 percent, or roughly three cases out of every 1,000 injuries.

That figure has remained largely stuck in the consciousness of public health authorities, despite growing evidence that the "three out of a thousand" estimate pertained more to untreated source patients with late-stage, symptomatic disease—the more likely scenario in 1989—than to estimates based purely on needlestick injury alone.

A meta-analysis conducted in 2006 largely confirmed those doubts. In reviewing 21 different studies, the researchers found that the pooled estimates suggested that the risk of acquiring HIV was more along the lines of 0.13 percent if the needlestick injury were the only risk factor. Only when the source patient has an AIDS diagnosis—namely, a CD4 count below 200 cells/mL and/or an AIDS-defining illness—did the estimate rise to 0.37 percent.

What was, perhaps, more important to note was that, of the 21 studies reviewed, 13 concluded an actual risk of 0%. Such disparities in research only served to add to the contentiousness already surrounding the issue of HIV risk in occupational health care settings.

CDC Examines Confirmed and Suspected Cases

In the January 9, 2015 issue of Morbidity and Mortality Weekly, CDC officials identified 58 confirmed and 150 possible cases of occupationally acquired HIV between the years 1985 and 2013.

Confirmed cases were those in which the health care worker was established to be HIV-negative while the source patient was shown to be HIV-positive. By contrast, possible cases were those in which the HIV status of the source patient was unknown or no documented link was established between the health care worker and source patient.

Of the 58 confirmed cases, all but four occurred between the years 1985 and 1995, just prior to the advent of antiretroviral therapy (ART) and the release of the first U.S. guidelines for the use of post-exposure prophylaxis (PEP) in cases of accidental HIV exposure.

Since 1999, only one confirmed case of occupationally-acquired HIV has ever been reported to the CDC. (That case involved a lab researcher who, in 2008, was working with a live HIV culture.)

While the CDC report in no way lessens the importance of PEP in cases of needlestick and other percutaneous injuries, it does suggests that, in the words of the researchers, "more widespread and earlier treatment to reduce patient viral loads" has contributed to the almost complete mitigation of HIV risk insofar as occupational exposure is concerned.

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