Transmission of hepatitis B in the health care setting: the elephant in the room ... or the mouse?

Received 23 January 2007; accepted 29 January 2007; electronically published 21 March 2007. Potential conflicts of interest: B.M.A. reports no potential conflicts; W.S. W. is a member of a data safety monitoring board that considers research vaccines for Merck and has received consultation fees from MedImmune. Reprints or correspondence: Dr. Ban Mishu Allos, A2200 Medical Center N, Vanderbilt University School of Medicine, Nashville, TN 37232 (Ban.Mishu.Allos@vanderbilt.edu). The Journal of Infectious Diseases 2007;195:1245–7 2007 by the Infectious Diseases Society of America. All rights reserved. 0022-1899/2007/19509-0003$15.00 DOI: 10.1086/513436 Most infections with hepatitis B virus in the United States occur as a result of specific high-risk behaviors. Most, but not all. Approximately 1.2 million people living in the United States have chronic hepatitis B virus infection [1]. Each year, another 8000 acute infections—mostly in adults— are reported to the Centers for Disease Control and Prevention (CDC) [1]. Many of these infections are the result of sexual activity (both heterosexual and homosexual) or intravenous drug use; however, up to one-third report no risk factors for infection [2]. Although it is likely that a large number of these risk-deniers simply are unwilling to acknowledge behaviors they may view as socially stigmatizing, it also is possible that some have acquired their hepatitis B infection in nonclassical ways. The blunt epidemiologic tools used in recent decades to assess risks of transmission have been important and useful. Nevertheless, finer implements may be needed to tease out smaller but perhaps substantial risk factors. This need is illustrated in the report published in this issue of the Journal by Redd et al. [3]. They describe a 60-yearold, white, non-Hispanic woman who was not sexually active, did not use intravenous drugs, and who had no contacts with persons with hepatitis B virus infection. She went to her dentist in October 2001 for routine tooth extractions. There, despite the oral surgeon’s adherence to standard infection control precautions, she was infected with hepatitis B virus. The oral surgeon and all the office staff were tested, and none had serologic evidence of infection with hepatitis B virus. How did this happen? The meticulous investigation that ensued demonstrated that this unfortunate woman’s virus was identical to virus isolated from an hepatits B surface antigen–positive 36-year-old woman who had hepatitis B infection dating back to at least 1999. The chronically infected woman had visited the same oral surgeon on the same day and had had 3 teeth extracted just 161 min before the index patient had a similar procedure. The authors conclude that patient-topatient transmission of hepatitis B infection occurred in the dentist’s office and also state that such transmission appears to be rare. How certain should we be that events similar to this are, indeed, rare? Ought we to be confident that the magnitude of the problem is small (the proverbial mouse), or might we be dealing with a hidden elephant? We suggest that the current burden of health care–acquired bloodborne infection is largely unknown because only modest efforts have been made to identify such cases and quantify the risk. A series of circumstances in this particular case led to the investigation that identified the source of the 60-year-old woman’s infection. The New Mexico Department of Health (DOH) did what some local and state health departments would have done—they conducted a routine investigation of the index patient’s newly diagnosed hepatitis B infection. In similar circumstances, if no traditional risk factors are found, the investigation typically stops. However, for reasons that are not entirely clear, when the DOH and the CDC could find no traditional risk factors to account for this infection, they looked further. They began by searching the state’s registry of patients with hepatitis B to identify the epidemiologic link between the source and index patient. Subsequent genotyping of viruses obtained from both women established that the younger woman was the source of the older woman’s infection. Thus, the investigators coupled traditional “shoe leather” epidemiology to newer molecular techniques to create an even more pow-