IFNB1 and infection: To determine the effect of hMPV infection on STAT1 and STAT2 activation in response to IFN-β treatment, A549 cells were mock-infected or infected with hMPV, at an MOI of 0.5, for 6 or 15 h, followed by IFN-β stimulation for 1 h, time of maximal STAT1 phosphorylation in response to the used concentration of IFN-β treatment (data not shown).