zombie survival campaign & how to make it plausible

Part of this idea came from me liking the "ongoing story" potential of zombie survival. Like, you can start out with this group and just keep going until all the original members are dead. I wouldn't use zombies but I like them as a good background / cannon fodder enemy. And fuck it, it's good for attracting "normies" which I want because I think they would be most into it. They're all into the Walking Dead.
Another part of this idea came from my friend and I's huge dissatisfaction with State of Decay. I liked the premise, hell I may just rip off the starting event. Oh you come back from your camping trip to find the world in shambles. It clashes with a few of my ideas for opening scenarios but I can find a way to work it in.
My biggest problem is what I call initial infection vector. Cause Max Brooks is obviously full of shit, and I think that even a Walking-Dead-style plague where "everyone is infected lmao" is too slow. Something needs to cause a good 50% of the population to die and become zombies within, say, 72 hours. That's the only reason that (1) it will actually shock the players and give them trouble, instead of giving them months to set up a cabin in the woods before the zombies even become a problem, and (2) actually fully overwhelm the United States government and infrastructure.

So I am going with your average bloodborne bite-borne zombie virus, with a few differences. One, fuck the 24 hours turning time that Walking Dead and Max Brooks seemed to use. One of my favorite parts of the Contagion video game was that you could get hit by a zombie and start to become "infected" and your screen would grow gray and stuff owuld sound weird until you turned. This took place over the course of 3 or 4 minutes. Now, I'm not sure I want it *quite* that fast, but I want something pretty close. Basically, you get bit, you got time to say goodbye and eat a last meal, but it's going to be painful because you are feeling stranger and stranger. So getting bit means you're likely to either cap off a bunch of zombies then yourself, or lead them off with a grenade, or something else cool. I want this infection to move fast. World War Z may have been a shitty movie (I enjoyed it, personally) but I liked how tense and overwhleming the first few minutes were when zombies just took over everything in hours.

So, I can't decide if I should have waterways get infected? Or a vaccine that most people are getting? Or maybe just 50% of the population has to be immune? I am trying to think of something that would infect a good 25 to 50% of the population over a few days, but would have something in common that I could use to explain the characters being spared (hence why a camping trip start might not be a bad idea).

Whaddya think? inb4 i'm a faggot for running a zombie campaign. Gives me a chance to use pic related. And sorry for splitting into 3 posts, I was sick of getting the "field too long" error message. Thanks for any advice you may have /tg/

Alien virus from a meteor. Gives you free reign to say how it mutates because "lol its brand new"
Control the virus, control the zombies.

Also one thing that always angered me in old games was how enemies knew where you were, it's just how games were, but this can help you here, have the dead seek out the living, not just wander, they can smell living people miles away, those living held up in cities are what keep the huge hoards there, since that's the closest flesh source nearby.
>Imagine a sky scraper surrounded by the city's entire (un)dead inhabitants trying to claw it's way into where one guy stockpiled a huge amount of food/is eating the dead bodies of the workers who he is holding at gun point.

No attempt at a zombicide campaign or a 3x3 (or more) survival fest?

With all the expansions there's no way it's not the go to zombie apocalypse game...

>>50312650
For the initial vector, the first and best thing that comes to my mind is food. Fast Food. McDonalds drops its burger prices by half because they've developed lab-grown beef. This beef is contaminated of faulty, whatever, bam, theres your immediate chunk of the population infected. You also have an ability to say oh the government or terrorists or x scary thing infected the meat or whatever.

Motorcycle Mongols are neccessary.