There　are　many　challenges　to　constitute　the　linkage　from　the　macroscale　to　the　microscale　and　analyze　the　multiscale　model.　We　proposed　a　bidirectional　coupling　model　with　standard　incidence　which　includes　the　interaction　of　between-host　transmission　dynamics　and　within-host　viral　dynamics,　and　investigated　the　dynamic　behaviors　of　the　multiscale　system　on　two　time-scales.　We　found　that　the　multiscale　system　exhibits　more　complex　dynamics　including　backward　bifurcation,　which　means　that　the　usual　thresholds　for　infection　control　or　virus　elimination　obtained　from　the　epidemiological　model　or　virus　dynamic　model　may　not　act　as　threshold　parameter　under　a　certain　condition.　There　may　be　multiple　epidemic　equilibriums,　one　of　which　is　stable,　although　the　basic　reproduction　number　is　less　than　1.　We　numerically　examine　the　synergistic　impact　between　the　macro　and　micro　dynamics.　In　particular,　increasing　the　drug　efficacy　can　decrease　the　prevalence　of　disease.　The　contact　rate　may　affect　the　number　and　size　of　equilibria　of　viral　dynamics　model　by　inducing　the　occurrence　of　backward　bifurcation.　The　finding　suggests　that　the　effective　control　measures　may　include　both　the　reduction　in　contact　rate　or　transmission　rate　at　the　population　level　and　the　increase　in　drug　efficacy　at　the　individual　level,　and　using　these　control　measures　together　can　effectively　control　the　diseases.　©　2020　the　Author(s),　licensee　AIMS　Press.