Well in the interest of involving everyone...

Shall we decide exactly how far the infection has spread? I pondered on the infection having spread across the United States and most of the Americas, with the exception of some rural areas and some countries in South America. There may be a number of military bases dotted in the most remote locations, with enough high security to hold the land for a while. 

The infection is likely to have spread overseas through carriers and infected holiday makers. Might have been some plane crashes. A few or many countries within Europe could be infected, whether in the early stages or not; we can decide how fast the infection spreads.

Thoughts so far?