Bibliographical noteFunding Information:
Stud)' supported in part by research grant 1746 from the.~ew York State Health Research Council and research grant AI-15886 from the United States Public Heahh Serice *Professor of Pathology, Emeritns, Harvard Medical School. Constfltant in Pathology, Brigham-Wonaen's Hospital, Boston, Massachttsetts. ?Professor, Departntent of Tropical Public l lealth, Harvard School of Public i-tealth, Boston, Massadmsetts. +Assistant Professor, Department of Pathology, School of ,Medicine, State Uifiversity of New York at Stony Brook. Research Scientist, Bureau of Disease Control, New York State Departlnent of Health, Stony Brook, New York. w Associate, Departutent of Tropical Public Heahh, Harvard School of Public Health, Boston, Massachusetts.