Sporadic CJD is the most commonly occurring form of the disease, but is still very rare.
Although the precise cause of sporadic CJD is unclear, it is has been suggested that normal brain protein may change sporadically and abnormally to become a prion by "misfolding".
The majority of sporadic CJD cases occur in adults aged between 45 and 75, with symptoms typically developing between the ages of 60 and 65.
Each year in the UK, sporadic CJD will affect around 1 or 2 people in every million. There were 110 recorded deaths from sporadic CJD in the UK in 2017.