Fear The Walking Dead has rewritten the rules around amputating limbs to avoid zombie bites, making the trick much more dangerous than before. Even those with only a casual awareness of zombies know a bite from the undead is not good news. In The Walking Dead's universe, a direct chomp is 100% fatal... even if no one can figure out why. The entire population is already infected with the virus, so bites don't pass the zombie pathogen directly, leading many to believe it's the bacteria inside a zombie's mouth that finishes a person off. That doesn't make sense either, however, because even a bite from a freshly-turned zombie in The Walking Dead is a death sentence.
While The Walking Dead still hasn't figured out its transmission science, one rule remains steadfast - if the bitten body part is removed before infection spreads, that person can be saved. Rick Grimes saved Hershel Greene from a zombie bite by reacting quickly and amputating his leg. June did the same for Virginia in Fear The Walking Dead season 7, and both shows contain various other instances of the technique sparing someone's life. These amputations usually carry two major risks. If the amputation isn't carried out promptly, the infection spreads and the bite victim still dies. As in the case of Chad Coleman's Tyreese, amputation can also result in blood loss that kills the person anyway.
Fear The Walking Dead season 7's "Padre" has now introduced a strange middle-ground to the zombie bite limb trick, where amputation simultaneously works... and doesn't. In her flashback, Alicia Clark is trapped by the blast from Teddy's nuclear missile, and a zombified Senator Vasquez seizes the free meal by taking a chunk out of her arm. Knowing what to do, Alicia brutally hacks off the afflicted limb and wakes up a week later worse for wear but, more importantly, still alive. Several months later in Fear The Walking Dead's present day, Alicia still hasn't turned, but her condition is worsening. She tells Morgan that the amputation was too late, and while removing her arm slowed down the infection, her doom is sealed.
Though it's easy to dismiss Alicia's self-diagnosis as the ramblings of someone with zero medical expertise, Andrew Chambliss (Fear The Walking Dead showrunner) strongly suggests in his post-episode interview that Alicia's slow-burn bite is genuine, saying, "We've seen many characters bit by walkers... but we haven't actually seen anyone battle a walker bite long term."
Assuming Alicia's condition is real, this adds a frightening new wrinkle to The Walking Dead's zombie rule book. Previously, audiences believed an infected limb amputated too late meant the victim would die as with any other bite. Alicia's arm removal is apparently dragging her infection out over an unnaturally long period, which completely changes how the virus behaves in the Walking Dead franchise. Characters could carry zombie bite symptoms for months, but still go about their daily business until suddenly dropping dead an indeterminable amount of time later - and no drug or procedure could prevent that outcome. This rule could easily be exploited by future Walking Dead writers, allowing a character to get bitten, but potentially cling on for multiple seasons after the fact.
For this reason, there's still a strong chance Alicia is wrong about her fate in Fear The Walking Dead season 7, and Andrew Chambliss was partaking in a spot of harmless misdirection to protect spoilers. As pointed out by Will, Alicia's fever eventually faded following the loss of her arm. It returned and has been plaguing her ever since, but that would indicate sepsis or tetanus as a far more likely diagnosis. Alicia condemning herself to death could be nothing more than a self-defense mechanism to cope with the trauma of Teddy's bomb, her bunker isolation, and the responsibility of becoming a leader - something Morgan seems to recognize when he calls her out for the "zombie sat-nav" idea. In all likelihood, Alicia's amputation had the intended effect, and proper medical attention from June - or anyone with actual medical knowledge - is all she needs.