The presence of viral diseases in reared aquatic organisms in Italy dates back to 1963, when viral haemorrhagic septicaemia has been described. From then on five more diseases have been officially identified and described in reared fish (infectious pancreatic necrosis - IPN; spring viremia of carps - SVC; infectious haematopoietic necrosis - IHN; lymphocystis - L and iridovirus of cat fish - ICF) and two in reared Crustacea (Monodon Baculovirus disease - MBVD and Baculovirus Penaei disease - BPD). The presence of the diseases cause each year severe economic losses in the national aquaculture. VHS, which causes about 40 thousand millions lira economic losses, represents undoubtedly the biggest biological risk. To reduce that heavy damage a RHS control program was started on a voluntary basis in 1978 and continued later on an official basis.