Association of IL-33 with asthma during RSV infection. Association of IL-33 with asthma during RSV infection. Based on animal models, IL-33 may be induced in the lungs of infants. IL-33 stimulates group 2 innate lymphoid cells (e.g., nuocytes) to propagate and release the asthma-promoting cytokines IL-4, IL-5, and IL-13. Sloughing of infected ciliated bronchial epithelial cells is mediated by the RSV accessory protein NS-2, which transmits infection into the lower respiratory tract. Bacterial coinfections during RSV infection are common, and prior colonization with potentially pathogenic bacterial species may be a risk factor for severe RSV infection. Cameron Griffiths et al. Clin. Microbiol. Rev. 2017; doi:10.1128/CMR.00010-16