细胞病变作用（英语：Cytopathic effect，简称：CPE）是细胞出现异常的生长或突变，通常和病毒感染有关。在病毒培养的组织琼脂上，病毒的扩散受到了紧密琼脂的限制。所以病毒只能感染旁边的细胞。被病毒感染后的细胞通常会在病毒分离后死亡所以在琼脂上留下透明的圈。

Cytopathic effect or cytopathogenic effect (abbreviated CPE) refers to structural changes in host cells that are caused by viral invasion. The infecting virus causes lysis of the host cell or when the cell dies without lysis due to an inability to reproduce. Both of these effects occur due to CPEs. If a virus causes these morphological changes in the host cell, it is said to be cytopathogenic. Common examples of CPE include rounding of the infected cell, fusion with adjacent cells to form syncytia, and the appearance of nuclear or cytoplasmic inclusion bodies.