Understanding pathogen transmission on inanimate surfaces: Insights from respiratory fluid droplet composition and drying dynamics

This study investigates how pathogen‐laden respiratory droplets transfer diseases via inanimate surfaces. Respiratory fluid ejections containing pathogens pose a significant health threat, especially in high‐traffic areas such as hospitals, public transport, restaurants, and schools. When these droplets dry on surfaces, they form deposits that can transfer pathogens to healthy individuals through contact and can be ingested via the oral or nasal route. The study examined the effects of varying salt and mucin concentrations in respiratory fluid droplets containing Pseudomonas aeruginosa . Results showed that P. aeruginosa viability increased 10‐fold at elevated mucin concentrations, while changes in salt concentration had minimal impact. Adhesive properties of the deposits were analyzed using atomic force spectroscopy and scotch tape test. Pathogen transfer from the deposit to a fingerprint patterned model thumb at different relative humidity (RH) levels was assessed using confocal microscopy, showing significant pathogen transfer at elevated RH. Out of 10 6 CFU/mL pathogens in deposits, 17%‒38% are potentially transferable, with most of the transfer occurring from the droplet's edge deposits. The study demonstrated that the combined variation in salt and mucin concentrations significantly influences the evaporation, flow, and precipitation dynamics of droplets. These changes, in turn, affect the solutal deposition and distribution of pathogens within the droplet, ultimately altering the survivability and transmissibility of the pathogen.