[1] NEW YORK BLOOD CTR, LINDSLEY F KIMBALL RES INST, EPIDEMIOL LAB, NEW YORK, NY 10021 USA
[2] COLUMBIA UNIV, SCH PUBL HLTH, DIV EPIDEMIOL, NEW YORK, NY 10027 USA
[3] NIAID, INFECT DIS LAB, BETHESDA, MD 20014 USA
[4] CENT BLOOD BANK, TEL AVIV, ISRAEL
[5] NAVY MED RES UNIT 2, TAIPEI, TAIWAN
[6] REGA INST MED RES, LEUVEN, BELGIUM
[7] INST EPIDEMIOL, SARAJEVO, YUGOSLAVIA