It matters who they appeared to because it effects how likely it is to be an effect of the room, and how likely it is to carry on out into the halls. Like- it's perfectly possible that an infected person arrives here from your world, and we're all totally fucked, like you said. But it's more likely that a room wanted to screw with you, so made it appear to be happening even though it really wasn't, and there's no danger of contageon.