title: A case-control study of sporadic Creutzfeldt-Jakob disease in the United Kingdom: analysis of clustering.
abstract: BACKGROUND
  The authors investigated whether cases of sporadic Creutzfeldt-Jakob disease (CJD) had lived closer to one another at some time in life than individuals without sporadic CJD. Such a phenomenon would be compatible with some cases resulting from transmission.
  
  
  METHODS
  UK sporadic CJD cases occurring from 1990 to 1998 were identified. Age-, sex- and hospital-matched controls were recruited. Lifetime residential histories were obtained by interview, usually with a proxy respondent. With use of Monte Carlo simulation, the residential proximity of cases during various time periods was compared with that expected in the absence of any clustering, using the information collected on the controls.
  
  
  RESULTS
  Two hundred twenty sporadic CJD disease cases and 220 controls were included. Cases lived closer together than might be expected in the absence of any disease-clustering mechanism. This evidence became stronger as the critical period during which residential proximity was required to have occurred extended further into the past.
  
  
  CONCLUSIONS
  These findings are consistent with some sporadic Creutzfeldt-Jakob disease (CJD) cases resulting from exposure to a common external factor. The rarity of sporadic CJD suggests that repeated point-source outbreaks of infection are more likely to explain our observations than direct case-to-case transmission. Identifying sources of such outbreaks many years after the event will be extremely difficult.
authors.affiliation: Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: L
authors.initials: L
authors.lastname: Linsell
authors.forename: S N
authors.initials: SN
authors.lastname: Cousens
authors.forename: P G
authors.initials: PG
authors.lastname: Smith
authors.forename: R S G
authors.initials: RS
authors.lastname: Knight
authors.forename: M
authors.initials: M
authors.lastname: Zeidler
authors.forename: G
authors.initials: G
authors.lastname: Stewart
authors.forename: R
authors.initials: R
authors.lastname: de Silva
authors.forename: T F G
authors.initials: TF
authors.lastname: Esmonde
authors.forename: H J T
authors.initials: HJ
authors.lastname: Ward
authors.forename: R G
authors.initials: RG
authors.lastname: Will
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D016000:Cluster Analysis; D007562:Creutzfeldt-Jakob Syndrome / Q000453:epidemiology* / Q000635:transmission; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D011159:Population Surveillance; D012111:Residence Characteristics; D013997:Time Factors; D006113:United Kingdom / Q000453:epidemiology