There's no tiptoeing around it anymore, 'The Walking Dead' has a new killer on the loose: a super-flu! Sunday's most recent episode "Infected" hit home literally and figuratively, complicating the survivors' already-fragile existences with the threat of disease around every corner, but who's next to fall victim in next week's "Isolation?" Find out in the latest clip!

Tyreese might have yet another cause to grieve after finding Karen's burned body, now that it looks like his sister Sasha has come down with the deadly flu! The first clip from "Isolation" sees Sasha reluctantly resigned to her fate in the isolation ward with Dr. S, but all is not as it seems in the quarantine zone. Other infected survivors are seemingly paid little attention, while others already succumbed are locked up rather than disposed of! Could Dr. S. be our mystery firebrand, all in the name of science?

Elsewhere, ‘The Walking Dead’ season 4 features ‘The Wire’ star Lawrence Gilliard, Jr. as comic character Bob Stookey, and will introduce ‘Southland‘ vet Michael Cudlitz as Sgt. Abraham Ford, Josh McDermitt as Eugene Porter, ‘Twilight‘ vet Christian Serratos as Rosita Espinosa, and Alanna Masterson as a new mystery character. The returning David Morrissey’s villainous Governor has been upgraded to series regular, though beyond this season his involvement seems unlikely.

Take a look at the latest 'Walking Dead' in the clip above, and tell us what new horrors you think "Isolation" has in store in the comments!