It turned out that right before Anastasia and Lucien arrived at the hall where everyone was holding the farewell party, the frightening news about the widespread rise of man-eating creatures had already spread among them.
The source of the news is none other than Eclair, the daughter of the couple who's involved in the making of this crisis. It seems like she's actually aware that this is going to happen despite the nonchalance she has shown to the issue earlier.
But then, nobody there but Anastasia knows that. That's why when she went ahead and told everyone that she was already infected by the virus, chaos broke out.
At first, they are shocked to see her materializing before them all of the sudden. They easily recognized her as the baker's daughter who had gone missing. Secondly, there's her unsightly appearance.