AIDS is a disease that causes the body’s immune system to fail to function against various bacteria, fungi and viruses. The disease is transmitted by a virus present in the blood and semen of patients suffering from AIDS. The virus is not found universally in the population, but is confined to certain groups. These so-called high-risk groups are promiscuous homosexual males, mainline drug addicts and, until recently, haemophiliacs. Promiscuous sexual contact among homosexual men causes increased risk of infection by blood-blood or blood-semen contact. Drug addicts are at risk through shared use of hypodermic needles. Infection with the virus need not produce symptoms, but its presence can be established by a special blood test. Only a limited number of those infected become ill, with symptoms such as sore throat, fever, skin eruptions, pain in the joints and muscles and swollen lymph nodes. An even smaller proportion (about 10 per cent) develops AIDS. Roughly six months to a year after infection weight loss, fever, persistent diarrhoea, nocturnal perspiration and skin and mucous membrane infection set in, together with a particular sort of skin tumour (Kaposi’s sarcoma). It has not yet proved possible to detect the virus itself in the blood, although a special test shows whether the patient has been in contact with the virus; this is applied in the case of blood donors, and their blood is not used if the test is positive. For this reason patients with blood diseases are not in the high-risk groups. An infected patient may remain in normal contact with society. The virus cannot be transmitted by kissing, tears, sweat, sneezing, coughing, or mutual contact with glasses, cutlery etc. More care is required during sexual contact. The use of condoms affords good protection against the AIDS virus. Drug users are advised always to use clean syringes and needles and never to share equipment. There is no known medicine or vaccine against AIDS. The majority of people contracting the disease die in the course of time from infections against which their bodies are no longer immune.