[Variant Creutzfeldt-Jakob disease in France: estimating the number of cases related to travel to the United Kingdom between 1980 and 1995].
BACKGROUND
The outbreak of variant Creutzfeldt-Jakob disease (vCJD) cases rose serious concerns about secondary transmission of the disease, particularly through blood transfusion. Protective measures leading to the exclusion of potentially infectious blood donors were settled: in France, donors who had stayed more than one year in the UK were excluded. In this work, which was part of a larger study aiming to estimate the French epidemic of vCJD, the number of vCJD cases who were infected during a trip to the UK was estimated. Those estimates may notably enable the assessment of such exclusion measures.


METHODS
The particular age-related structure in vCJD cases is taken into account in our simulations considering birth cohorts in the population. The total French exposure is simulated assuming the main source of infection to be dietary through consumption of mechanically recovered meat (MRM) manufactured from British bovine carcasses. Then, using a "back calculation" algorithm, all infected individuals required to produce a consistent epidemic (6 vCJD cases in 2003) was simulated. This study was exclusively focused on the part of the exposure linked to trips (beef MRM consumed in the UK while traveling) and on cases resulting from this exposure.


RESULTS
The influence of exposure linked to trips to the UK was greater in the youngest cohort (6.3% of the total exposure) while it only accounted for 3.3% and 1% in the 1939-69 and in the pre-1939 birth cohorts respectively. Overall, exposure resulting from trips in the UK can be neglected with regards to the exposure linked to the consumption of MRM produced in France from British bovine carcasses. Consequently, French vCJD cases that would have been infected in the UK are very unlikely to occur (median: 0 case, IC 95%: (0-2)). Nevertheless, if such cases occur, they would probably occur in subjects born after 1969 and their onset would take place before 2010. Thus, unlike the situation in BSE-free countries, the causal relationship between travel in the UK and occurrence of vCJD cases cannot be underlined in France, as trips only account for a small part of the French exposure.


CONCLUSIONS
Since trips in the UK slightly contribute to the overall French exposure, excluding people who travelled in the UK from blood donation would not influence the risk of secondary transmission.
Chadeau-Hyam
M
M
INSERM U 360, Hôpital de La Salpêtrière, 75651 Paris Cedex 13. marc.chadeau@chups.jussieu.fr
Alpérovitch
A
A
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002417:Cattle; D007562:Creutzfeldt-Jakob Syndrome / Q000453:epidemiology*; D004196:Disease Outbreaks; D016643:Encephalopathy, Bovine Spongiform / Q000453:epidemiology / Q000635:transmission*; D005260:Female; D005506:Food Contamination; D005602:France / Q000453:epidemiology; D006801:Humans; D008297:Male; D008460:Meat / Q000382:microbiology; D008875:Middle Aged; D014195:Travel; D006113:United Kingdom