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Background: Experimental results evidenced the infectious potential of the dental pulp of animals infected with transmissible spongiform encephalopathies (TSE). This route of iatrogenic transmission of sporadic Creutzfeldt-Jakob disease (sCJD) may exist in humans via reused endodontic instruments if inadequate prion decontamination procedures are used., Methodology/principal Findings: To assess this risk, 10 critical parameters in the transmission process were identified, starting with contamination of an endodontic file during treatment of an infectious sCJD patient and ending with possible infection of a subsequent susceptible patient. It was assumed that a dose-risk response existed, with no-risk below threshold values. Plausible ranges of those parameters were obtained through literature search and expert opinions, and a sensitivity analysis was conducted. Without effective prion-deactivation procedures, the risk of being infected during endodontic treatment ranged between 3.4 and 13 per million procedures. The probability that more than one case was infected secondary to endodontic treatment of an infected sCJD patient ranged from 47% to 77% depending on the assumed quantity of infective material necessary for disease transmission. If current official recommendations on endodontic instrument decontamination were strictly followed, the risk of secondary infection would become quasi-null., Conclusion: The risk of sCJD transmission through endodontic procedure compares with other health care risks of current concern such as death after liver biopsy or during general anaesthesia. These results show that single instrument use or adequate prion-decontamination procedures like those recently implemented in dental practice must be rigorously enforced.

Background: Presently, all patients with clinical variant Creutzfeldt-Jakob disease in the United Kingdom have been Met-Met at codon 129 of the PrP gene. There is much worry about the possibility of a second wave of the epidemic in the 60% of the United Kingdom population which are not Met-Met., Methods: A mathematical model of a putative United Kingdom variant Creutzfeldt-Jakob disease epidemic that could occur in non Met-Met is derived. The risk of infection is assumed to parallel the Met-Met risk which has been previously modelled. The reason for the present absence of clinical non Met-Met cases is assumed to be a longer incubation period in these subjects than in others. The incubation period is assumed to be lognormally distributed. The means and coefficients of variation compatible with the present absence of clinical cases are systematically searched., Results: We show that the present absence of clinical cases of variant Creutzfeldt-Jakob disease in the Met-Val or Val-Val population can be compatible with a second wave only if the mean incubation period is more than 25 years. The best estimates of the size of the second wave are always below 250. A fraction of these cases however will never be observed, as they will die from other causes before the onset of the new variant., Conclusion: The mean incubation period values compatible with the absence of non Met-Met clinical cases that we found are not implausible, and the possibility of a second wave cannot yet be ruled out. However, should this second wave occur, it would be below 250 in the worst hypothesis.

The size of the variant Creutzfeldt-Jakob Disease (vCJD) epidemic in the United Kingdom is a major public health concern and a subject of speculation. The cases are young (mean age = 28). Assuming that the risk of developing the disease in susceptible exposed subjects decreases exponentially with age after age 15, that all infections occurred between 1980 and 1989, and that the distribution of the incubation period is lognormal, we estimate that the mean duration of the incubation period is 16.7 years [95% confidence interval (CI): 12.4 to 23.2] and that the total number of cases will be 205 (upper limit of the 95% CI: 403).