Alright, let's see how this sounds.
The background goes something like this...
The first time you heard the rumors of Yangtze Rabies was two months ago. It was an otherwise normal evening when you turned on the TV and saw a two minute bit on CNN about a sudden outbreak of disease in the Yangtze river basin in China. The pathogenesis was rapid and transmitted through fluid contact, resulting in fever, coma, aggressive behavior, and death. With China's heavy-handed quarantine and official assurances that the infection was contained, the story was downplayed and quickly forgotten in the western mainstream, no more significant than the brief SARS outbreak a decade earlier.
A week later, the social media lit up as a handheld video of a bloodied Asian woman devouring a live chicken went viral. Suddenly new videos began appearing every hour: people savagely attacking bystanders, operating rooms covered in blood, tank battalions rolling through downtown Beijing, a view of a valley along the Yangtze covered in a massive firestorm. Suddenly, "zombie" was the most-searched term on Google. At first, US and NATO were tight-lipped besides pantomiming concern for China's treatment of the so-called Yangtze rabies. As videos of similar events in Russia, India, and Japan appeared, public cries of conspiracy and coverup began to rise. The mainstream media continued to downplay the seriousness of the crisis, claiming many of the videos were doctored or part of a massive hoax.
After an Afghanistan army base went dark the same day a video of Seoul in flames went viral, the US government finally relented and admitted that Yangtze rabies was, in fact, reanimating the dead. Armed forces around the world were recalled. Airports were locked down, coastlines constantly patrolled by an unprecedented number of ships. A military cordone was placed over the east coast. The last you saw before the cable inexplicably gave out was a declaration of martial law by the president.
In the next two weeks, Boston was encircled by the US military, blocking all ways in and out of the city. If you had access to the internet, you'd find that similar blockades were forming around New York, Washington, Los Angeles, and other major cities. It was a quarantine on a massive scale, but it was too little too late. Travelers from abroad had returned infected and, slowly but surely, began their own outbreaks. The west coast was the first to burn, as millions of refugees -- many of them infected -- swamped the blockade and engulfed California and Washington. Miami and New Orleans suffered a similar fate a week later.
At first, Boston seemed secure. The military, although heavy handed, made sure no infected made it through the checkpoints. Schools and universities still held classes, the water and electricity stayed on. Even Logan Airport, with military and supply planes constantly flying in over Boston harbor, was as busy as ever. Aside from the epidemic of suicides, and the occasional execution of an infected trying to enter the city, local life was pretty much normal. People worried about their distant loved ones, but Yangtze rabies was almost never spoken of in public. Out of sight, out of mind.
Ten days ago, a train full of infected blasted through the military cordon and crashed into North Station. The military reacted quickly, but it was too late. Many of the infected vanished into the subways, and within days, the downtown was a death trap. Societal order quickly collapsed as a quarter of a million people tried to flee into the suburbs, only to be trapped by the military blockade. In the chaos, the order to fire was given, and any road leading out of the city became a bloodbath. Despite the massacre, the military power was eventually overwhelmed, resulting in the complete breakdown of civilization in Boston. Utilities stopped working, the internet vanished, and all that remained of communication equipment were hardlines.
Your character will start this game seven days after the fall of the military. For reasons left to you, she'll find herself trapped in the downtown. Maybe she went in search of a family member or supplies. Maybe she was trapped there and unable to escape. I leave that up to you.
That's the background. How does it sound?