Although further research is needed, the most recent thinking is that
prions are tiny protein particles without DNA or RNA which have the ab
ility to infect humans or animals, Prions cause slow infections which
are fatal, experimentally transmissible, evoke no immune resistance fr
om the infected host and are more resistant to disinfectants and chemi
cal or physical agents than the other micro-organisms that proliferate
in the infected host, Update no evidence of possible passage by mouth
from cows to men with consequent illness.