The present invention uses ex vivo human airway cultures to assess the human transmissibility and replication competence of influenza and coronavirus strains. By comparing pandemic influenza A subtype H1N1 and highly pathogenic avian influenza H5N1 as reference strains, the transmissibility risk of various viruses was evaluated and categorized. Additionally, an in vitro model evaluated virus-induced impairment of alveolar fluid clearance (AFC) as an indicator of disease severity. The study revealed correlations between bronchus viral replication, human transmission, AFC impairment, and clinical disease severity across different influenza and coronavirus strains.

A method is provided for reducing cytokine secretion in virus-infected cells through treatment with specific alkylamides. The method includes identifying a cell infected with a rhinovirus or influenza virus and administering one or more alkylamides, such as Dodeca-2(E),4(E)-Dienoic acid isobutylamide, to reduce cytokine release, particularly interleukin-8 (IL-8). In certain embodiments, the alkylamides are in purified form and may be derived from Echinacea purpurea. The method may further comprise measuring IL-8 secretion to assess efficacy of the treatment. Another aspect provides a screening method for identifying specific alkylamides effective against respiratory virus infections by comparing cytokine secretion levels between infected cells treated with purified alkylamides and those treated with Echinacea purpurea ethanolic extract. Alkylamides demonstrating reduced cytokine secretion and a selectivity index greater than 10 are identified as therapeutic candidates for mitigating cytokine-mediated inflammatory responses in respiratory viral infections.