In studies by Kellar et al., juvenile C57BL6 mice (3-week-old) but not adult mice (8-week-old) exhibited a distinct myeloid recruitment pattern in response to RSV infection, αSma expression (indicative of myofibroblast activity) and increased hyaluronan deposition in the lung parenchyma (72 h post-infection). The gene discussed is ACTA1; the disease is infection.