[1] CNR, IST FISIOL CLIN, I-56100 PISA, ITALY
[2] UNIV LONDON LONDON SCH HYG & TROP MED, LONDON WC1E 7HT, ENGLAND
[3] ROYAL HOSP SICK CHILDREN, DEPT CHILD HLTH, GLASGOW G3 8SJ, LANARK, SCOTLAND
[4] MINIST PUBL HLTH & ENVIRONM, INST HYG & EPIDEMIOL, BRUSSELS, BELGIUM
[5] UNIV HOSP FERRARA, FERRARA, ITALY
[6] INSERM, PARIS, FRANCE
[7] INSERM, F-13258 MARSEILLE, FRANCE
[8] UNIV HOSP, PERUGIA, ITALY
[9] UNIV PADUA, I-35100 PADUA, ITALY
[10] UNIV GRONINGEN, DEPT MED GENET, NL-9700 AB GRONINGEN, NETHERLANDS
[11] UNIV MALTA, MSIDA, MALTA
[12] UNIV BILBAO, BILBAO, SPAIN
[13] ODENSE UNIV HOSP, DK-5000 ODENSE, DENMARK
[14] INST MORPHOL PATHOL, LOVERVAL, FRANCE
[15] MINIST PUBL HLTH, LUXEMBOURG, LUXEMBOURG
[16] ROYAL LIVERPOOL UNIV HOSP, LIVERPOOL, MERSEYSIDE, ENGLAND
[17] EASTERN HLTH BOARD, DUBLIN, IRELAND
[18] UNIV COLL HOSP, GALWAY, IRELAND
[19] QUEENS UNIV BELFAST, BELFAST BT7 1NN, ANTRIM, NORTH IRELAND
[20] PROVINCIAL INST HYG, ANTWERP, BELGIUM
[21] UNIV LAUSANNE, CH-1015 LAUSANNE, SWITZERLAND
[22] UNIV HOSP, STRASBOURG, FRANCE
[23] UNIV ZAGREB, ZAGREB 41000, CROATIA