Abstract
Despite low case numbers the variant Creutzfeldt-Jakob disease epidemic poses many challenges for public health planning due to remaining uncertainties in disease biology and transmission routes. We develop a stochastic model for variant CJD transmission, taking into account the known transmission routes (food and red-cell transfusion) to assess the remaining uncertainty in the epidemic. We use Bayesian methods to obtain scenarios consistent with current data. Our results show a potentially long but uncertain tail in the epidemic, with a peak annual incidence of around 11 cases, but the 95% credibility interval between 1 and 65 cases. These cases are predicted to be due to past food-borne transmissions occurring in previously mostly unaffected genotypes and to transmissions via blood transfusion in all genotypes. However, we also show that the latter are unlikely to be identifiable as transfusion-associated cases by case-linking. Regardless of the numbers of future cases, even in the absence of any further control measures, we do not find any self-sustaining epidemics.
Highlights
The incidence of variant Creutzfeldt-Jakob disease in the UK has declined considerably since the epidemic peaked in 2000, with currently less than 5 cases arising each year [1]
When the first variant Creutzfeldt-Jakob disease (vCJD) cases were reported in the late 1990s, the small numbers combined with lack of knowledge of both the potential transmission routes and key epidemiological parameters meant that projections of the future epidemic were highly uncertain [24,32]
Following the peak in cases in 2000, and their subsequent decline to low numbers, it has for several years been possible to characterise the oral transmission route in the MM genotype and estimate associated epidemiological parameters with a reasonable degree of precision [28,31]
Summary
The incidence of variant Creutzfeldt-Jakob disease (vCJD) in the UK has declined considerably since the epidemic peaked in 2000, with currently less than 5 cases arising each year [1]. There remains concern about the possibility of future cases arising both from past exposure in previously unaffected genotypes and through person-to-person transmission. The latter is warranted given that 3 of the 171 cases due to definite, probable or possible vCJD to the end of 2009 have been linked to blood transfusions [4,5,6] and these could herald the start of a potential secondary wave of cases of unknown scale. To date there is no evidence that any transmissions via these transmission routes have occurred
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