Celia is no Hershel. She's worshipping the other party, as we saw in the last episode, when she pinned Luis' picture under the grim face carved in the wood. She knew what her true son were. Hence devotion to the dead, and slaughtering Mexican Catholics.
The dead has been a long tradition in Mexican and Southern American cultures. And it continues growing strong, especially in that Trump hated nation, south-side US border. But what surprised me was that AMC actually confirmed that Celia is true to her words. The dead has been here for a long time and Daniel has seen them before.
In my own work, I based the plague similarly to south, but in my case it started in the caves of Northern Africa. In TWD's world, they're suggesting that the original source could be found from jungles of South America. In a place that Inka's used to rule for a long time.
Maybe they dug up something from the jungles. Something we haven't seen, but what has been confirmed in the main series by the CDC scientist. The other part in the question is: will there ever be a cure? was confirmed by Celia, when she admitted that the turned will stay that way, until they become dust.
What I loved in this episode was how the series embraced Mexican culture fully. Their people believe that the dead visit them in this world, and that what happened to Daniel. But then again I also loved Travis finally casting aside his pacifist nature and embrace his psychopathic side in this world that has gone crazy.
He and Chris has been on the kill-list for a long time, and this way, we can assume they will never come back in the main-cast. If they will, then Chris has accepted Travis vision and taken pacifism in his heart, while the world around them remain truly hostile.
We know they have in their heart an ability to survive even the most dire situation. Yet their nature is the most diabolical threat to the existence of FTWD's crew.
What did you thought?