[1] Minist Hlth, Lao Trop & Publ Hlth Inst, Vientiane Capital, Laos
[2] Swiss Trop & Publ Hlth Inst, CH-4123 Allschwil, Switzerland
[3] Univ Basel, Basel, Switzerland
[4] Minist Hlth, Dept Radiol, Mahosot Hosp, Vientiane Capital, Laos
[5] Robert Koch Inst, Immunizat Unit, Berlin, Germany