The international occurrence of the acquired immunodeficiency syndrome. 
Through December 1984, 9932 cases of the acquired immunodeficiency syndrome have been reported, mainly from North and South America and Europe; 85% of these cases occurred in the United States.  Haiti and the United States have the highest incidence rates, 59 and 36 per million population, respectively.  Rates in the United States range from 0.3 (beginning of 1981) to 10.4 (end of 1984).  Brazil, Canada, Denmark, Switzerland, France, West Germany, the United Kingdom, and the Netherlands show a slower increase.  Homosexual men and intravenous drug users are still the main risk groups in the United States and Europe.  The disease is prevalent in heterosexual Haitians and Africans whether they live in their own countries or abroad.  Cases of the syndrome have been identified in Zaire, Rwanda, Zambia, and Uganda, but its full extent is not yet known.  Consistent with the general history of epidemics, the appearance of geographically separated sites of incidence of the syndrome could be linked to population migrations; however no evidence has been found to identify an index location.