Acquired immunodeficiency syndrome in the United States: an analysis of cases outside high-incidence groups.

From 1 June 1981 through 31 January 1984, 201 cases of the acquired immunodeficiency syndrome were reported involving persons who could not be classified into a group identified to be at increased risk for this syndrome. Thirty-five had received transfusions of single-donor blood components in the 5 years preceding diagnosis of the syndrome and 30 were sexual partners of persons belonging to a high-risk group. Information was incomplete for most remaining patients, but because many of these patients were demographically similar to populations recognized to be at increased risk for the syndrome, previously identified risk factors may have been present but not reported for some of them. Additionally, a few persons who met the case definition for the syndrome probably had other reasons for their opportunistic disease and did not have the acquired immunodeficiency syndrome. The slow emergence of the acquired immunodeficiency syndrome in new populations is consistent with transmission mediated through sexual contact or parenteral exposure to blood.