Bidirectional transfer of influenza virus between hands and environmental surfaces under multifactorial conditions

Influenza viruses continue to circulate worldwide, posing persistent challenges to public health. Indirect contact transmission (i.e., transmission via contaminated surfaces, or fomites) is a recognized pathway for influenza spread and depends on multiple factors governing virus transfer between hands and fomites. However, current studies on the determinants of influenza virus transfer rates remain limited in scope and integration. This study quantified, using reverse transcription quantitative PCR (RT-qPCR), the transfer of influenza A virus genomic RNA between hands and surfaces (fomites) under the combined effects of multiple factors. A total of 74 transfer experiments encompassing 444 individual transfer events were conducted using artificial skin. Statistical analyses were performed to evaluate how material type, contact direction, contact force, and environmental conditions influence the transfer of viral RNA. The results demonstrated significant differences in transfer rates among surface materials on horizontal planes (P < 0.001), and a pronounced directional effect (P < 0.001). In contrast, contact force (P = 0.313) and environmental conditions (P = 0.564) showed no statistically significant overall effects. These findings highlight the importance of differentiated disinfection strategies considering surface orientation. Moreover, this study provides refined estimates of viral RNA transfer parameters that quantify hand-fomite transfer, supporting quantitative exposure assessment and informing evidence-based environmental cleaning and hand-hygiene strategies.