Come on, we all know, the book contains specific reference to Patient Zero originating in China. I am telling you the Media Bureau or something like that checks everything, anything that they deem offensive to China. China may contain flaws in their system, and there are many things in their laws that I personally don't like, but they have the right to ban a work of fiction which does not portray their country in favorable light. They have the right to even ban any work of fiction just because.
But having said that, the Chinese are missing quiet a good chunk of revenue by refusing WWZ playdate because I bet this is the kind of movies young Chinese moviegoers love to see on the big screen. Judging by the impressive run of STID, the Chinese is ready for thought-provoking scifi genre. I won't be surprised WWZ earning $50-60M ala MoS & STID.