[1] CTR DIS CONTROL & PREVENT,NATL CTR INFECT DIS,DIV VIRAL & RICKETTSIAL DIS,ATLANTA,GA
[2] UNIV VIRGINIA,HLTH SCI CTR,DEPT PEDIAT,CHARLOTTESVILLE,VA
[3] UNIV SAO PAULO,INST BIOMED SCI,SAO PAULO,BRAZIL
[4] UNIV COLORADO,CHILDRENS HOSP,HLTH SCI CTR,DENVER,CO 80218