Ok folks here's the scenario.
You are the President of the United States and a zombie apocalypse has broken out in New York City. You have shut down the all ways out of the city and the outbreak seems pretty much confined to the city. The military has strongly suggested using a tactical nuclear missile to destroy the city and stop the outbreak once and for all.
As the president you don't have much to go on as scientist and the CDC are telling you they don't know if destroying the city will stop the outbreak. They don't know for sure if whatever caused the outbreak has escpaed the city as they don't yet know the length of the incubation period. There are also millions who have yet to be infected trapped inside the city and no way to evacuate them.
So what do you do Mr./Mrs. President? Do you give the order to fire that missile and slow down the outbreak or leave the city blocked off?