Azithromycin Inhibits the Replication of Zika Virus

Background: The emergence of Zika virus (ZIKV) is associated to dramatic complications in fetuses and neonates. As there is no vaccine and no drug to prevent and treat ZIKV infections, there is an urgent need to have active drugs against ZIKV that can be used during pregnancy. Large screening strategies suggested that azithromycin (AZ) has an in vitro activity against ZIKV, we provide additional data supporting this hypothesis. Methods: We tested the efficacy of AZ on ZIKV-infected Vero cells at a concentration that can be reached in vivo in amniotic fluid. We conducted two experiments with addition to infected cells of a single dose or multi doses of 50 mg/L of AZ, and analyzed ZIKV replication by immunofluorescence assay (IFA) and by measuring viral RNA loads at different times up to 96 h post-infection (hpi). Results: Addition of a single dose of 50 mg/L of AZ prevented replication of ZIKV during 48 hpi; after 48 hpi, ZIKV replication was detected by IFA but viral RNA loads remained lower than in untreated infected cells. ZIKV replication was inhibited by addition of multi doses of 50 mg/L of AZ. Conclusions: Our data confirm the in vitro activity of AZ against ZIKV. Since there will be no active specific drugs and vaccine available soon against ZIKV, AZ might be the first compound that could prevent and treat ZIKV infections, with the advantages of being an approved and safe drug usable during pregnancy.