Some 1600 zombies were rounded up and annihilated by the Chinese government at the onset of the zombie apocalypse. Suspecting the motivation for the Chinese government was political, the CIA found out about the mass extermination, even though the Chinese suppressed the information. For those select few who knew these facts, the mass annihilation was presumed to be the beginning of the end of life as we know it. However, it was later determined that the actual commencement of the apocalypse started earlier, and not in China.
The true origin of the zombie apocalypse was discoverd by CIA rogue black-ops agent Chad Halverson. His adventures are detailed in the epic Zombie Apocalypse: The Chad Halverson Series.