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Eurosurveillance, Volume 7, Issue 10, 06 March 2003
Articles

Citation style for this article: Andrews NJ, Molesworth AM. Decline in the incidence of variant Creutzfeldt-Jakob disease in the UK. Euro Surveill. 2003;7(10):pii=2174. Available online: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=2174

Decline in the incidence of variant Creutzfeldt-Jakob disease in the UK

Nick Andrews (nick.andrews@phls.org.uk), and Anna Molesworth, Public Health Laboratory Service Communicable Disease Surveillance Centre, London, England.

By the end of December 2002 the number of cases of confirmed or probable variant Creutzfeldt-Jakob Disease (CJD) reported in the United Kingdom (UK) had reached a total of 129 (http://www.doh.gov.uk/cjd/stats/jan03.htm). Quarterly analyses are performed that estimate the underlying trend in vCJD incidence. These enable short term predictions for the expected number of deaths in the next year as well as estimates of the total number of individuals with symptom onset yet to be identified (http://www.cjd.ed.ac.uk/vcjdq.htm).

Previous quarterly analyses of these data have indicated an exponentially increasing trend (1, 2). The most recent analysis, however (table and figure), showed significant evidence of a departure from this pattern; the underlying incidence was estimated to have reached a peak in 2000 of about 5 deaths and onsets a quarter and then to have declined to 3.9 deaths per quarter (3.2 onsets) at the end of 2002.

Table. Annual cases by onset and death

Year
Onset
Death
     
1994 8 0
1995 10 3
1996 11 10
1997 14 10
1998 17 18
1999 29 15
2000 24 28
2001 16* 20
2002 0* 17
Total
129 121


* Numbers of cases may rise in subsequent quarters due to reporting delay

A slowing down in the previously increasing trend means that short term projections for the number of deaths in the next year as well as the numbers of unobserved onsets are now much lower than in past analyses. An additional 12 cases are expected bringing the total number of cases with onsets by the end of December 2002 to 141 (95% confidence interval 135 to 151). A total of 13 deaths were predicted for 2003 (95% confidence interval 5 to 23). The analysis of the deaths data was reported in detail recently (3). In addition, back calculation models which attempt to estimate the total size of the epidemic are affected; a recent analysis based on deaths to the end of 2001 gave a prediction of a total of 80 further deaths by the year 2080 with a 95% confidence interval of 10 to 7000 (4). Revised estimates using 2002 data, including upper confidence interval estimates, will be much lower than those reported previously.


Observed (-o-) and expected (-e-) quarterly incidence of vCJD onsets. Fitted quadratic trend* (___) is given with its 95% confidence limits (...).

*includes adjustment for delay from onset to diagnosis


It is encouraging that trends in deaths from vCJD are consistent with the epidemic having reached a peak, but this should be interpreted with caution; it is possible that the epidemic may have a very long tail with some cases occurring many years after exposure; or we may see more than one peak to the epidemic at a later date as individuals with non methionine homozygous genotypes at codon 129 of the PRNP gene (which so far accounts for all cases) are affected. There is also the theoretical possibility of secondary transmission through human to human spread. Continued surveillance and research to investigate these possibilities is therefore important.

The most recent monthly CJD statistics for the UK are available at http://www.info.doh.gov.uk/doh/IntPress.nsf/page/2003-0090?OpenDocument.


References :
  1. Andrews N. Incidence trends and short term predictions for variant Creutzfeldt-Jakob disease in the United Kingdom. Eurosurveillance Weekly 2001; 5: 011115. (http://www.eurosurveillance.org/ew/2001/011115.asp).
  2. Andrews N. Incidence trends and short term predictions for variant Creutzfeldt-Jakob disease in the United Kingdom - update. Eurosurveillance Weekly 2002; 6: 020725. (http://www.eurosurveillance.org/ew/2002/020725.asp).
  3. Andrews NJ, Farrington CP, Ward HJT, Cousens SN, Smith PG, Molesworth AM, et al. Deaths from variant Creutzfeldt-Jakob disease in the UK. Lancet 2003; 361: 751-2.
  4. Ghani AC, Ferguson NM, Donnelly CA, Anderson RM. Factors determining the pattern of the variant Creutzfeldt-Jakob Disease (vCJD) epidemic in Great Britain. Proc R Soc London B Biol Sci 2003; published online. (click here for abstract).

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