Figure 4 is a stacked bar graph demonstrating the changes over time (according to year of death) in the classification of definite and probable prion disease cases in Australia by aetiology (sporadic, familial and iatrogenic) from 1970 to 2014. Over the time-frame, a positive trend in the number cases is observed as depicted in Figure 3. The graph shows that the large majority (91%) of Australian cases are sporadic, followed by a small proportion of familial cases (7.9%) and iatrogenic cases (1%).