Day 20-23: CDC reports of the brain-controlling amoeba mutating to full airborne status, with the zombies quickly outnumbering the living. The US Army straights-up decides to evacuate uninfected civilians.

Day 24-40 : Zombies start appearing in major cities across the contiguous United States. Florida State Police arrest a scientist who was spotted releasing the amoeba in Miami. 

Investigations reveal he is part of a cult wanting to punish the world for pitying the undesirables such as the homeless. However, he is a small fry.

Anarchists abuse free speech laws to spread misinformation, leading to more openly defying quarantine orders.

The National Guard and US Army are pushed to their limits. Countries across the world start repatriating their own citizens and conduct mandatory screening for people coming from the US.

Day 40- Day 60:

Mutation has accelerated infection. Towns and a few major cities have been overrun.

Outbreaks occur in countries like Egypt, Czech Republic and Mexico, as customs officers have been bribed by infected passengers.

Day 60- Day 100:

45% of the US has been overrun and efforts are focused on evacuating uninfected civilians. Singapore, Israel, Canada are the first to send in evacuation helicopters to assist the US Army.

The rest of the world halts flights from the US completely.  

The US government flees to Mount Weather Emergency Operations Center.

Day 101: 

Investigations reveal the creator is a scientist working at Area 51, who sustained slight brain damage after an attempted robbery by a homeless person. 

Whereabouts are unknown.