MAPK3 and viral infectious disease: To determine whether the MEK/ERK signaling pathway is involved in EV71 infection, we examined the levels of total and phosphorylated MEK1/2 and ERK1/2 at 0 h, 1/2 h, 2 h, 4 h, 8 h and 24 h p.i. As shown in Table 1, the results showed that virus infection did not enhance mRNA levels of MEK1/2 and ERK1/2 molecules in PCR assay, but significantly elevated their phosphorylation (Figure 3A and C).