IL4 and infection: IL-4-treated primary human macrophages produce an average of [2.58 +/- 2.07] x 104 pfu/ml (mean +/- SD) of infectious DENV 48 hours after infection with MOI 1 DENV2, strain 16681, covering a >40-fold range from 2.3–97.5 x 104 pfu/ml.