Minimal Influenza Virus Transmission From Touching Contaminated Floors and Metal Door Levers: Laboratory Study II

Influenza is generally understood to be transmitted through inhaling virus-contaminating aerosol/droplets or contact with virus-contaminated environmental surfaces (or fomites). However, the risk associated with transmission through contact with fomites is hypothetical, lacking solid quantitative evidence. In our previous paper, we demonstrated through a series of experiments that the probability of influenza virus transmission from touching contaminated surfaces of face masks is minimal (Sci Rep 2024, 14, 20211). In the present study, we expanded upon this study by conducting an experimental evaluation of the likelihood of influenza transmission from dried fomites under three specific scenarios: (1) when a floor/table lies within the trajectory of artificial coughs, (2) when stainless-steel door levers are exposed to viral spraying (simulating cough), and (3) when door levers are exposed to viruses on the grasping hand. The fingertips contacting the above fomites formed on the surfaces were washed into a rinsing medium. Subsequently, we evaluated the rinsing medium for viral content using plaque-forming assay to detect the viable viruses and real-time quantitative PCR assay to detect the viral genes. We found that viable viruses were rarely transmitted to fingertips from the above fomites even when the viral loads in the viral fluid contaminating the fomites far exceeded that seen in real life. Consequently, we conclude that the probability of contact transmission of influenza via dried fomites is negligible or minimal under the scenarios studied here.