It involves the presence of basophilic inclusions in the gonads and the presence of virus particles that have been classified as papovaviruses/[5]papillomaviruses-polyomaviruses. They may be propagated during spawning or by vertical transmission,[1] lack an envelope[6] and have an icosahedral shape.[4]Ovocytes appear to be among the infected cells and their nuclei are hypertrophic, and the host does not noticeably respond with an immune response.[3] A hypertrophy has also been observed in spermatocytes;[2] in general an enlargement of the gametes is observed.[1] Such viruses have been found in Australian and North American oysters as well. The health of the oysters is not noticeably affected by viral gametocytic hypertrophy.[5][3][1][4]
^ abWatermann, B. T.; Herlyn, M.; Daehne, B.; Bergmann, S.; Meemken, M.; Kolodzey, H. (1 August 2008). "Pathology and mass mortality of Pacific oysters, Crassostrea gigas (Thunberg), in 2005 at the East Frisian coast, Germany". Journal of Fish Diseases. 31 (8): 621–630. Bibcode:2008JFDis..31..621W. doi:10.1111/j.1365-2761.2008.00953.x. ISSN1365-2761. PMID18700939.