Did he make the Tar Zombie too? I hate when zombies say brains.
But yeah, I think that if there was a zombie plague, it would have to be slower-acting than 28 Days Later 5-seconds-and-it's-over infection. Maybe it starts out looking like something else, maybe flu-like symptoms. After a few days he starts coughing up small amounts of blood, prompting him to go to the doctor. The doctor would probably refer him to a major hospital, coughing up blood is generally a bad sign, once he's there, there are probably hundreds of people there. He's sitting in the crowded waiting room, sick people are everywhere, sick people with hurting immune systems. The symptoms get worse, maybe he goes into a coughing fit, spraying virus particles safely encased in droplets of water, people inhale them and become infected. A more interesting case would be if the virus started affecting his brain here, and he attacked someone. In the more subtle case, many people could be infected without noticing it. Maybe the disease takes years to reach zombie stage, in that case there could be a huge population of disease carriers once it starts affecting the brain. Since people travel, it would be all over the world at that point.
EDIT: And Kagus is right, if an obvious zombie shows up, people are going to panic. They're all going to mass-run away from it, pushing and shoving, knocking people over, the zombie gets to those people and bites them, game over for them.
Also, has anyone played the Zombie Infection Simulation and its modifications? They're a lot of fun, I found one that lets you drop bombs to see how many people you can save. I managed to rescue 55 out of 5000.