It started like any other day . . .
Almost.
For several weeks, news programs around the world had been reporting on a mysterious flu-like virus infecting millions of people world-wide. Symptoms included high fever, sweating, chills, hallucinations, "coma", and eventually death. It was treated with a multitude of anti-viral medications but none seemed to cure the illness entirely although, initially, the medications seemed promising in at least slowing down the infection. The cause of the illness was still under investigation when, like a trigger was pulled, people with the illness began dropping like flies. In a panic, the bodies were quarantined to prevent contamination but days later, the "dead" bodies awoke. This death-like state must have been another trait of the virus, and "coma" was added to the list of possible symptoms.
It wasn't a coma, of course, and the previously dead bodies were released from quarantine. Chaos ensued as the dead created more dead, attacking those who released them and, eventually, those victims would do the same. Each new dead person could infect multiple living people, so it didn't take very long for the outbreak to become uncontrollable.
Most people who survived the frenzy fled for their lives. Cities were not safe. Nothing was safe. Government and military officials attempted to create "safe-zones" scattered throughout the country but how many of them were successful in keeping the illness at bay, is unknown.
