one of my colleagues at work is a virologist and I found out the following interesting fact yesterday;
When someone suffers from glandular fever (Epstein-Bahr), the body produces anti-bodies against any possible virus it can has ever been in touch with.
Glandular fever is diagnosed by mixing white bloodcells in with sheeps blood. If the sheeps blood congeals, you have glandular fever.
Ergo, every single person on earth has an anti-body against sheeps blood.