Two persons died in Spain from the human form of the mad cow disease in the Castilla-Leon region. The previous case was the first ever in the European country when one person died in Madrid three years ago.

Bovine spongiform encephalopathy or mad-cow disease emerged first in British cattle. It is deadly and has an unusually long incubation period of around 4 years. It also appears rarely in humans under a different form, called new variant Creutzfeldt-Jakob disease (vCJD or nvCJD).

The disease has already killed almost 200 people in Britain. It is unclear if the disease is transmitted to humans through consumption of infected meat, but this is the most likely path. The cattle in Britain get it from being fed the remains of other infected cows. The misfolded protein called a prion which carries the disease is much more resistant to heat than common viruses or bacteria, and it is generally believed that it is not destroyed by normal cooking processes.

Even though its human form is the most common human prion disease, it is still rare and only occurs in about one out of every one million people (except if you live in Britain). In more than 85 percent of cases, the duration of the disease between onset of symptoms and death is less than 1 year (median: 4 months). It is incurable and fatal.

Of the Spanish victims, one died on December 28 and the other on February 7, according to an unnamed spokeswoman for the health department in the central Castilla-Leon region, quoted by several news sources.