Creutzfeldt–Jakob disease (CJD) is a rapidly progressive, fatal and transmissible
neurodegenerative disease associated with the accumulation of misfolded prion protein in
the CNS. International CJD surveillance programmes have been active since the emergence,
in the mid-1990s, of variant CJD (vCJD), a disease linked to bovine spongiform encephalopathy.
Control measures have now successfully contained bovine spongiform encephalopathy and
the incidence of vCJD has declined, leading to questions about the requirement for ongoing
surveillance. However, several lines of evidence have raised concerns that further cases of vCJD
could emerge as a result of prolonged incubation and/or secondary transmission. Emerging
evidence from peripheral tissue distribution studies employing high-sensitivity assays suggests
that all forms of human prion disease carry a theoretical risk of iatrogenic transmission. Finally,
emerging diseases, such as chronic wasting disease and camel prion disease, pose further risks
to public health. In this Review, we provide an up-to-date overview of the transmission of prion
diseases in human populations and argue that CJD surveillance remains vital both from a public
health perspective and to support essential research into disease pathophysiology, enhanced
diagnostic tests and much-needed treatments