How did Guo Jia die in The Romance of the Three Kingdoms?

In Romance of the Three Kingdoms, Cao Cao returned from an expedition to Wuwan, and Guo Jia died of illness.

One of the five plans is that Guo Jia once offered a plan for Cao Cao, so it can be done quickly. At that time, in Puyang, Cao Cao's army and Lu Bu's army had a bitter battle and were finally defeated. Cao Cao said to the counselor, "You should rest here, and don't fall into the enemy's trap. I'm going to fight at once. "

After hearing this, Guo Jia only said four words: "The plan can be quick", which means that any plan is the result of judging the present opportunity, so that Cao Cao need not worry. Although Guo Jia didn't provide detailed operational principles and strategies, he told Cao Cao from the side that he didn't have to worry about the advisers in the rear, which relieved his worries and inspired Cao Cao's confidence, making him believe that his own strength could form a trend of grinding the enemy.

The second of the five moves is that Guo Jia once dissuaded Cao Cao from killing Liu Bei and let Liu Bei live. At that time, after Liu Bei surrendered, Cao Cao did not completely relax his vigilance against him, and gathered many advisers around him to discuss the countermeasures. Most people support Cao Cao to kill Liu Bei in order to avoid future troubles. Only Guo Jia dissuaded Cao Cao and let him cut Liu Bei some slack.