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Background: The emerging threat to global health associated with the Zika virus (ZIKV) epidemics and its link to severe complications highlights a growing need to better understand the pathogenic mechanisms of ZIKV. Accumulating evidence for a critical role of type I interferon (IFN-I) in protecting hosts from ZIKV infection lies in the findings that ZIKV has evolved various strategies to subvert the host defense line by counteracting the early IFN induction or subsequent IFN signaling. Yet, mechanisms underlying the counter-IFN capability of ZIKV and its proteins, which might contribute to the well-recognized broad cellular tropisms and persistence of ZIKV, remain incompletely understood. Results: Using RNA sequencing-based transcriptional profiling of whole blood cells isolated from patients acutely infected by ZIKV, we found that transcriptional signature programs of antiviral interferon-stimulated genes and innate immune sensors in ZIKV-infected patients remained inactive as compared to those of healthy donors, suggesting that ZIKV was able to suppress the induction of IFN-I during the natural infection process in humans. Furthermore, by analyzing the molecular interaction in a ZIKV NS4A-overexpression system, or in the context of actual ZIKV infection, we identified that ZIKV NS4A directly bound MAVS and thereby interrupted the RIG-I/MAVS interaction through the CARD-TM domains, leading to attenuated production of IFN-I. Conclusions: Our findings collectively revealed that ZIKV NS4A targeted MAVS and contributed to ZIKV immune evasion through abrogating MAVS-mediated IFN production. These findings obtained from patient studies have added new knowledge and molecular details to our understanding regarding how ZIKV mediates suppression of the IFN-I system and may provide a new basis for the future development of anti-ZIKV strategies. [ABSTRACT FROM AUTHOR]