Clinical score and survival rate of SPF-chickens after infection with HPAIV. Chickens were challenged with 105.5 ELD50 of FPV, FPV NS GD or FPV NS VN. n = ten chickens per group. Average clinical signs of the surviving chickens (A) and survival rate (B) from each group measured at different time-points after infection. The results were analyzed with the Kaplan-Meier method and the survival curves were compared by the log-rank and the Gehan-Breslow-Wilcoxon tests. No statistical differences were observed between the survival curves.