[1] IST SUPER SANITA, EPIDEMIOL & BIOSTAT LAB, VIALE REGINA ELENA 299, I-00161 ROME, ITALY
[2] MINIST AFFARI ESTERI, DIREZ GEN COOPERAZ SVILUPPO, ROME, ITALY
[3] UNIV LONDON LONDON SCH HYG & TROP MED, LONDON WC1E 7HT, ENGLAND
[4] OSPED SAN LUIGI, USL 34 REG PIEMONTE, ROME, ITALY