You Can Play It Like That.

You can play Infected like old D&D.

Present the players with the archetypes Scoundrel, Courier, Changed, and Seeker.  All the local encampments and enclaves are distrustful of them, but do have things they need - you can stay in their quarantine areas, and they'll try to get you to do jobs for them.  Most of those jobs involve going to places like hospitals, malls, and other places that are thronging with the dead and growing horrible and strange, but are filled with loot.

You can play Infected like Shadowrun.

Again, with the probably-outcast characters, and the not-very-friendly enclaves.  Add: There are also derelict and running camps loose on the streets.  Also add: Enclaves are also deep into praxis research, and they want you not only to run delves, but to sneak into other enclaves and get their research, mess with their scouting teams, and more.  Of course, those enclaves aren't trustworthy; they'll happily stab you in the back.

You can play Infected like Dogs In The Vineyard.

Make sure you offer the Badge as a cop, the Face up as a political type, and the Courier to drive as good archetype choices.  Start the players off as working for city government, and stuck in city hall, with the Mayor's office desperately coordinating efforts at the emergency sites in town (the enclaves-to-be) while everything goes to hell.  Appoint the characters as "emergency inspectors" for those enclaves as quickly as possible, and send them out.

You can play Infected like it's Twilight:2000
Give the characters a good reason to road trip, and a good amount of force.  Possibly start them as all being from a common home or base - and one that they're far from, but which might very well still be there to some extent.

You can play Infected like it's RIFTS.

Just start the game a good ways into the apocalypse, with a nice chunk of bonus starting XP, loads of praxis gear, human and maker micro-nations, and set up a few packages of Changed traits anyone can buy (at in-archetype costs) as different "species packages" forced onto those in some areas by the makers that rule them.

You can play Infected like it's Call of Cthulhu

Start the game a few weeks before the apocalypse, with the characters hot on the trail of some mysterious organization called "The Black Sun".

And you can play it just like it is, too.

Without a strongly-oriented setup, Infected defaults to a sandbox survival game, one where characters will need to live long enough to get into an enclave situation - and then will likely need to maintain it, to deal with problems in and around it, and build what they can as they fight the apocalypse and try to take some measure of control over their future.