AIDS virus. Coloured transmission electrom micrograph of Human Immunodeficiency Virus type 1 (HIV-1). The sample is strain IIIB, the standard culture strain. HIV is the causative agent of AIDS, a viral disease characterised by the loss of the body's cell- mediated immune response. The virus may be transferred between people through infected blood, semen or vaginal fluid. After a long incubation period the patient may first develop fevers, weight loss and enlargement of the lymph nodes. Patients will normally die from infections such as pneumonia or from cancers such as Karposi's syndrome. Magnification: x55,000 at 6x7cm size. x180,000 at 8x10"~LANDSCAPE"