Comparison of viral replication kinetics in A549 cells. A549 cells were infected with viral strains; NC2, NC8 and NC11 at MOI 2. (a) shows the viral titers in cell supernatants 24 and 48 h post infection (P < 0.0001). (b) shows viral mRNA levels in infected cells and (c) Nuclear localization of viral NP protein was noticeably slow in cases of NC8 infection at 4 h that led to no or negligible yield of viral progeny in cell cytoplasm at 8 h post infection. Red shows staining of viral NP protein and blue shows nucleus specific DAPI stain. Micrographs are taken at the magnification of 40 (for 4 h and 8 h) and at 20 for 24 h.