Based on our previous work and the present studies, we propose that future co-morbidity study of allergic airway inflammation and influenza should investigate the impact of asthma on the host susceptibility to viral infections when TGF-β is at the baseline, i.e when lung homeostasis has been restored after allergic challenge, to better mimic infections of asthmatic patients. The gene discussed is TGFB1; the disease is influenza.