In 1996 the devils began to get very sick and then die with large tumours on their faces. Devil facial tumour disease has greatly reduced the number of devils and now threatens their survival. In some areas 85% of devils have been found with the disease. In the places where the tumours were seen first, devil numbers have dropped by 95%. The tumour is spread by biting. Because the devils are all closely related (not enough genetic diversity), the tumour cells are not seen as new; so the devil's immune system does not fight it. In May 2008 the Tasmanian devil was listed as endangered. Programs are being tried by the Tasmanian government to reduce the impact of the disease. About 60 devils without the disease have been captured and are to be kept as a tumour free group for rebreeding. Scientists have been looking at ways to give the devils immunity but so far this has not worked.