Scary because: the terrible brain disease of cattle seems to be transmissible to people through a very unusual agent - a protein called the prion. The agent of transmission seems to be more durable than bacteria or viruses.

Also scary because many aspects of the disease are not yet known, and may not be known for a while because of its long incubation period (years).


Symptoms: In humans, mad cow disease (bovine spongiform encephalopathy, or BSE) is known as new variant Creutzfeldt-Jakob disease (nvCJD). Each disease slowly destroys brain tissue, leading to abnormal behavior, dementia and invariably to death.

How you get it: by eating meat infected with tissue from the central nervous system of an afflicted animal. The rate of transmission seems to be very small - maybe as small as 1 in a billion.