New patterns of infectious disease are always interesting and sometimes alarming. The appearance of a syndrome with a high mortality and including not one but a whole range of infections is both interesting and alarming. The interest is heightened by the syndrome including an unusual manifestation of an uncommon form of cancer, Kaposi's sarcoma. Thesyndrome occurs principally in homosexual men and first surfaced about 1979 in the form of major foci in the urban United States, particularly in New York and California. Of the first 300 patients described, 291 came from the United
States and only nine from six other countries, but several of these had recently been in the United States. More recently new reports have shown that the disease is now no longer confined to the United States nor entirely to homosexuals, nor to the male sex. Pathologically its essential basis is an acquired cellular immune deficiency, but the cause of this deficit at present eludes investigators, and, perhaps for this very reason, the malady excites an interest far beyond the columns of the medical press. The clinical picture is difficult to describe, or even to define, because of the diffuseness and incoherence of the syndrome. Of the first 300 patients, 290 were men, of whom over four fifths were under 45, and most were homosexuals. The 10 women were predominantly heterosexual. Patients may present with a pneumonia eventually diagnosed as due to Pneumocystis carinii or with Kaposi's sarcoma, or with both. Many patients, however, appear to have had fever, lymphadenopathy, loss of weight, and diarrhoea before the principal illness, especially before the pneumocystis pneumonia. Of the 300 patients mentioned above, 135 had pneumocystis