[1] YALE UNIV, SCH MED, DEPT EPIDEMIOL & PUBL HLTH, NEW HAVEN, CT 06520 USA
[2] MINIST SALUD, INST NACL HIGIENE RAFAEL RANGEL, CARACAS, VENEZUELA
[3] ARMED FORCES RES INST MED SCI, DEPT VIROL, BANGKOK 10400, THAILAND
[4] CISEI, INST NACL SALUD PUBL, CUERNAVACA, MORELOS, MEXICO
[5] MINIST SALUD, INST NACL SALUD, BOGOTA, COLOMBIA
[6] UNIV VALLE, DEPT MICROBIOL, CALI, COLOMBIA
[7] INST OSWALDO CRUZ, DEPT VIROL, BR-20001 RIO DE JANEIRO, BRAZIL
[8] FUNDACAO NACL SAUDE, INST EVANDRO CHAGAS, BELEM, PARA, BRAZIL