The scientific literature gives few descriptions of viral contamination in biotechnological productions of recombinant proteins or viral vaccines (Table X) . Nine cases have been published indicating that viral contamination can be acquired via the serum source (in 7 out of 9 cases) or the culture medium (in 1 out of 9 cases). Biotechnological products were contaminated by different viruses, by those leading to a cytopathic effect (epizootic haemorrhagic disease virus) but in most cases by those which have no effect on the morphology of the contaminated cells (Minute Virus of Mice (MVM), BVDV, BPyV, bluetongue virus, reovirus). In cases where the viral infection leads to observable morphological effects, the contamination is easily detectable. However, those viruses which do not lead to a modification of the morphology and/or growth characteristics of the cells require methods such as RT-PCR, PCR, bulk in vitro testing. Or alternatively the onset of diseases in animals administered with the test material. These virus positive products were not delivered in the case of the products destined for human use, because the virus detection was performed before product release (Garnick, 1996; Rabenau et al., 1993; Harasawa and Sasaki, 1995) , however, with respect to the live attenuated veterinary vaccines, several incidents of disease in vaccinated animals were reported (Kreeft et al., 1990; Wilbur et al., 1994; Falcone et al., 2000) .