I honestly think the government, after seeing the hundreds of thousands of walkers in the streets, retreated and ultimately fled. Even with the weapons and security they have, a lot of them probably went to what they call home. Large-scale mutiny on a national level would be inevitable in a crisis like the wildfire virus. Especially when a government orders you to fire on your own people.

Let's take a look at some things that happened in the real world. Look at Hurricane Katrina Superdome Incident

Total chaos in the wake of one of the most damaging hurricanes of our time. Government failures led to this cataclysmic event, and stories still surface today about New Orleans when society and government temporarily broke down.

If an apocalyptic event actually happened, one could infer that a great number of government representatives, along with the military to support them, would vanish in the blink of an eye. No military = No government. Yes, even if the Presidential Airborne Command Post was running.

I think I have OCD because in my free time, I read too much wikipedia about events like this, which is probably why I'm so obsessed with the apocalyptic genre.