1. VAR; Department of Virology; Groeselenberg 99 B-1180 Brussels Belgium
2. UMR 1161 AFSSA-ENVA-INRA; 23 Avenue General De Gaulle 94704 Maisons-Alfort France
3. ARSIA; Avenue Alfred Deponthière 40 B-4431 Loncin Belgium
4. FASFC; WTC III, Simon Bolivarlaan 30 B-1000 Brussels Belgium