Wei et al. [66] also infected Muscovy ducks with A/Duck/Guangdong/212/2004 (H5N1) and A/Duck/Guangdong/383/2008 (H5N1) viruses, and found that TLR3 was upregulated in brain tissues over three days post-infection, but downregulated in lung tissues. Here, TLR3 is linked to infection.