Okay, so during a recent interview with Andrew Lincoln, he revealed that the "new threat" appearing in Season 4 is:


But thank God he was kidding. However, it turns out that the real new threat was revealed by Robert Kirkman. In an interview, when asked about the new threat, he said this:

"Mother Nature is rearing it's ugly head at a time when we're completely incapable of combating it. This new threat is this Spanish flu-type sickness that is ravaging these people. That's really wrecking things for them. Aside from having The Governor (David Morrissey) looming on the horizon or any other kind of human threat that is out there, or zombies — which is something they're always fighting — they've also got to deal with this thing, which is possibly more deadly than anything they've faced yet."

And then Scott Gimple added:

"As far within the prison, there's a threat that doesn't come from the outside world, it comes from within the prison. We have a whole panel of threats this season. A virtual smorgasbord of threats."

A smorgasbord of threats. So, are you finally relieved by the fact that we now know what the "mysterious" new threat is? I am.