Exceptions That Prove the Rule

“The exception that proves the rule...” This often-misunderstood English language idiom, at least in its “loose rhetorical sense” [1], is highly applicable to the transmission from providers infected with blood-borne pathogens to their patients (ie, the rarity of these events helps characterize and define the miniscule risk for these transmissions in the practice of modern medicine). Decades of experience have taught us that providers infected with blood-borne pathogens pose a small but nonetheless detectable risk to their patients, specifically when the provider is performing what have now been termed “exposureprone invasive procedures” on patients. Because of this small but clearly detectable risk, particularly for providers infected with the hepatitis B virus (HBV), the optimal management of healthcare providers infected with blood-borne pathogens has been controversial. The risk for provider-to-patient transmission is so small that it cannot be measured with precision, and the small numbers of instances of provider-to-patient transmission of HBV, in essence, provide evidence for the “rule” that such transmissions are remarkably rare. In 1991, in great measure in response to the occurrence of 6 cases of iatrogenic human immunodeficiency virus (HIV) transmission in the practice of a Florida dentist [2–4], the Centers for Disease Control and Prevention (CDC) issued guidelines recommending that healthcare workers who are infected with HIV or HBV and who have circulating hepatitis B e antigen (HBeAg) and who desire to perform such exposure-prone procedures can continue to perform such procedures only after first notifying the patient of the healthcare provider’s infection as well as after consulting an expert review panel to determine, “under what circumstances, if any, they may continue to perform these procedures” [5]. These guidelines remained as the practice standard in the United States until 2010 when the Society for Healthcare Epidemiology of America (SHEA) published new recommendations about the management of providers infected with blood-borne pathogens [6]. Subsequently, in 2012, the CDC published “Updated CDC Recommendations for the Management of Hepatitis B Virus–Infected Health Care Providers and Students” [7]. These new, sentient guidelines represented a substantial departure from the prior US Public Health Service guideline published in 1991 [5] and now provide a clear approach to this problem for hospital, health departments, and occupational medicine providers. In this issue of Clinical Infectious Diseases, Enfield and coworkers report another well-documented instance of provider-to-patient transmission of HBV—documenting at least 2 instances of transmission of HBV to the patients of an HBV-infected orthopedic surgeon who also had a high circulating viral burden [8]. In 2012, such cases are clearly exceptional in the true sense of the word. Transmission of blood-borne pathogens from providers to patients has become exceedingly rare. The development and wide implementation of hepatitis B immunization, both specifically for healthcare workers as well as for the population at large, has had a profound influence on the prevalence of this blood-borne infection in the United States. Nonetheless, the influx of practitioners into the US healthcare delivery milieu from areas in the world where the prevalence of HBV infection is high (and, therefore, the likelihood of transmission from mothers to newborns is high, producing a significant population of individuals who have high circulating viral burdens and little evidence of liver disease) has provided an influx of US healthcare providers who are chronically HBV infected and who have high circulating HBV viral burdens. Whereas such practitioners do present a risk for transmission to patients during the conduct of exposure-prone procedures, the development of highly effective antiviral therapy for this infection provides a mechanism for reducing such practitioners’ circulating viral burdens, thereby minimizing the risk for transmission. Received 19 September 2012; accepted 24 September 2012; electronically published 16 October 2012. Correspondence: David K. Henderson, MD, NIH Clinical Center, Bldg 10 Rm 6-1480, 10 Center Dr, Bethesda, MD 20892 ([email protected]). Clinical Infectious Diseases 2013;56(2):225–7 Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2012. DOI: 10.1093/cid/cis876