The significant transmission means for AIDS are from blood to blood and from semen to blood. The groups at highest risk of contracting AIDS are male homosexuals and bisexuals, intravenous users of illegal drugs, and the sexual partners of the aformentioned groups. Regarding AIDS risk for prison staff, there is no epidemiological risk of catching the disease under the normal conditions of social contact or work performance. In the United Kingdom, there can be no compulsory blood testing performed on any inmate. Blood tests are conducted by medical officers only when there is a sufficient clinical reason to do so. Because the immune systems of AIDS patients are rendered ineffective by the AIDS virus, they are vulnerable to serious complications from various diseases. Prisons must be prepared to render to AIDS patients the same care they would receive in the community. In the United Kingdom, there are plans to expand hospital facilities at Brixton and to use other suitable hospital accommodations as required. The number of full-blown cases of AIDS in the British prison system has remained remarkably low, however, given the overrepresentation of high-risk groups in the prison population.