Nonetheless, elevated IL-1β [32] and TNF-α [33] levels have been reported in the later stages of infection with virulent PRRSV strains, and HP-PRRSV is known to induce systemic cytokine responses, including TNF-α, IFN-α, IL-1, and IL-6, around 7 dpi [34]. This evidence concerns the gene IL6 and infection.