Warning! This portion may contain spoilers for Marvel's What If..?. Read at your own risk!
It's a wonderful day to be a geek as Marvel and zombies go together in one show with Episode 5 of Marvel's What If..? titled What If.. Zombies?! where the heroes became flesh-eating monsters and there were only a few left. Bur first, what caused the apocalypse? How did it arrive to such a dire situation that in a few days, the whole world was infected?
What Caused The Zombie Apocalypse in Marvel's What If..? Episode 5
It was explained to Bruce Banner by Hope when they rescue him from zombie Stark, Wong, and Doctor Strange as he was taken to Earth by Heimdall to warn the planet of the coming of the Mad Titan. The world went mad first even before. New York was deserted and when he came face to face with Cull Obsidian and Ebony Maw, he was saved by the zombies, only to be a prey to them.
With the help of the cape of Doctor Strange, Banner survived the zombie heroes just in time for Hope and the rest to save him. They were hiding in the middle of buildings, a series of hallways put together and webbed by Spider-Man, suspended in mid-air, a genius idea that makes them unreachable by any zombie unless they're flying like Falcon.
Hope explained that it was her research that started everything. Like that in Ant-Man and The Wasp, she did everything she could to bring back her mother and Hank Pym went to the quantum realm to get her. However, in this reality, Janet Van Dyne contracted a virus there, one that turns people into zombies. Hope said that she wanted to bring her mother so much, she did not think of the repercussions.
Since Hope was exposed to the virus when her suit was scratched, she sacrificed herself and she took them to a camp in New Jersey, the one where Arnim Zola was found by Cap and Nat in Captain America: Winter Soldier, and Vision was there. He found a cure, a way to reverse the process of being a zombie, and he did it to Scott Lang.
The mind stone can emit a sub-frequency keeping the zombies at bay as encephalopathy affects the brain, and Vision reversed the process by targeted exposure. To do this, they need the frequency to be broadcasted through a satellite strong enough to reach the corners of the Earth. Since Vision was an android, the zombies didn't want to eat him.
However, he was only doing such for Wanda who got infected. Since she was too powerful, Vision cannot get through his frequency on her resulting in him feeding her the survivors. He realized his mistake, though, and took off the mind stone on his forehead to bring it to Wakanda.
In the end, only Peter, Scott, and T'Challa remained. Okoye, Kurt, Bucky, and Hulk were left behind. Hulk had to hold off Wanda. Still, a threat remains as zombie Thanos is waiting just outside Wakanda.
Marvel's What If..? Episode 5 is now streaming on Disney+.