RIGI and infection: In the current study, PR/8 infection up-regulated mRNA levels of RIG-I and MDA-5 mainly at 4 hpi, but the mRNAs of TLR3 and 7 mainly at 24 hpi (Figure 1B), which suggests that RLHs might be the early sensors and TLRs might be the late sensors for PR/8 in human AM.