[1] Aristotle Univ Thessaloniki, Dept Microbiol, Thessaloniki 54124, Greece
[2] Swedish Inst Communicable Dis Control, SE-17182 Solna, Sweden
[3] Natl Vet Inst, SE-75651 Uppsala, Sweden
[4] Linkopings Univ, Dept Clin & Expt Med, SE-58183 Linkoping, Sweden
[5] Karadeniz Tech Univ, Fac Med, Dept Infect Dis, Trabzon, Turkey
[6] Univ Zaragoza, Dept Anim Pathol, Zaragoza, Spain
[7] NIAID, Virol Lab, Div Intramural Res, NIH, Hamilton, MT USA