Results revealed that the expression of Cdc2 in PRRSV-infected cells was higher than that in mock-infected cells at 24 h and the expression of p-Cdc2(Tyr15) in PRRSV-infected cells was significantly higher than that in mock-infected cells at 48 h post-infection (Fig. 5a), which indicated the G2/M phase arrest caused by PRRSV infection is related with expression increase of p-Cdc2(Tyr15). The gene discussed is CDK1; the disease is infection.