To combat that trend, over three years from June 1991, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) comprehensively tested the potential ofa " Calicivirus", which causes rabbit haemorrhagic disease (RHD), for biological control of wild rabbits. The virus escaped from a quarantine compound on Wardang Island, South Australia, where the field tests were being carried out, and by late October 1995, it was recorded in rabbits at Yunta and Gum Creek, in north-eastern South Australia. By the winter of 1996, the virus was established in Victoria, New South Wales, the Northern Territory and Western Australia. The virus was discovered in these area by analyzing livers of dead rabbits. The success of the virus was found to be higher in dry areas, because of a benign calicivirus found in the colder, wetter areas of Australia, which was immunising rabbits against the more virulent form.