Viral load was determined by a plaque-forming assay and a ZIKV RNA copy number determined by qRT-PCR assay using sera and tissues collected three days post-challenge, an optimal time point to detect ZIKV infection in anti-Ifnar1 antibody-treated immunocompetent mice, including BALB/c (our unpublished data) [37]. The gene discussed is IFNAR1; the disease is Zika virus infectious disease.