Apocalypse Manila - Could zombies really exist?

My novel Apocalypse Manila is an apocalyptic zombie story. Could zombies really exist some day?  I was reading a zombie survivalist blog where a guy who blogged said he was a doctor. He talked about how ignorant the site hosts were because the living dead or zombies were physically impossible.  The brain could not control the body without the organs or blood flow. 

But think about all the things people thought were impossible in the past.  A hundred years ago people couldn't imagine cloning sheep or curing diseases with stem cell therapy. A few hundred years ago did people think we would be flying or going coast to coast in a few hours?  Did our ancestors think we'd go to the moon (some people still don't believe we did). Could zombie-like creatures become possible due to a future medical experiment gone astray? Maybe they wouldn't be exactly like the brain-only body controlled zombies we've come to know in current fiction, but something that looks similar. Maybe it will be a quickly spreading disease that spreads like a zombie virus.

Two questions for you.  Do you think zombie-like creatures will be possible someday?  What is the first thing you will do when the zombie apocalypse begins?