The causes of CJD are as follows:
- Sporadic (unknown cause): 85% and 90% of cases.
- Genetic CJD (conditions inherited from one or both parents): 10% to 15% of cases.
- Acquired CJD (infection from a medical procedure, such as a transplant or tissue graft): Less than 1% of cases.
- Variant CJD (contracted by eating beef from an animal with bovine spongiform encephalopathy): Only 232 confirmed cases since 1986. The most recent person with variant CJD died in 2019.