Cao Zhen's Death (Three Kingdoms [2010 TV series])

Historically, he died by illness. In the novel, while being ill, killed by insulting letter from Kongming, aka Zhuge Liang. But In TV series 2010 version, he died from...!
According to Wikipedia, Cao Zhen played by Zhao Jin, Cao Shuang played by Xia Tian and Sima Yi played by Ni Dahong (倪大宏).