Dr. Kwang Jingshu is a medical doctor in China and witness to one of the first known zombie attacks of the zombie war. As a character, his purpose is to set up many of the novel's various aspects.
Since he does so much in the set=up department, how about we tackle this character analysis with our handy friend, the bullet point:
• As a medical doctor, Kwang is able to give a detailed physiological rundown of the zombies. Mr. Joe Average might not know that a human's mouth is so packed with bacteria that it would most likely cause an infection around any serious bite and then find it weird when the zombie's bite had no infection around the munched-on area. But by having the first character a doctor, Brooks can give us all these details and more.
• Kwang scoffs at the "ignorant peasants" and their "stagnant superstitious" beliefs (2.1.7). His desire to study the zombies and not rely on the superstitious misinformation of others sets up the theme of the importance of education and knowledge.
• Even as a war-hardened veteran, he is "scared, truly scared" of "Patient Zero" (2.1.15). If a character so used to violence and gore can be so terrified of the zombies, then you can just imagine how a corporate executive or some poor Shmoop writer would feel coming face-to-face with these beasts.
• Kwang's flashback to his time as a wartime medic foreshadows the horror and fear of the war to come.
• The way the Chinese government handles the situation and jails Kwang provides us with more foreshadowing. In this case, it foreshadows the way the world's governments will completely mishandle the situation.
• Let's not forget the old woman who "had witnessed enough calamity [with] the warlords, the Japanese, the insane nightmare of the Cultural Revolution" (2.1.24). By comparing the zombies to "another storm," Kwang links the zombies symbolically to such life-shattering disasters like war—a comparison he will make again in chapter 9.6.
Kwang returns briefly at the end of the novel, but by that time, his work is already done. He's provided us with all the information we need to get the plot moving, the characters developing, and the themes a-churning in our minds. Not too shabby for a character who gets less than forty paragraphs of screen time page time.