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High-touch surfaces with moderate contamination levels as key nodes in microbial dissemination
Pengcheng Zhao1, Peihua Wang2, Tzehau Lam3
1Department of Mechanical Engineering, The University of Hong Kong, Pokfulam, Hong Kong, China; School of Energy and Environment, Southeast University, Nanjing, China.
Abstract:
Hand-touching of contaminated surfaces is an established mode of infection transmission. However, the role of touch-mediated pathogen spread remains debatable, as frequently touched surfaces may exhibit low pathogen loads. To inform disease-prevention protocols, this study experimentally and theoretically investigated contamination in surface-touch networks as a function of touch behaviours and pathogen sources. Observation of four settings containing bacterial tracer particles showed that while most surfaces were rarely hand-touched, networks were formed by several high-touch 'hubs'. Counterintuitively, heavy contamination was primarily exhibited by some rarely touched surfaces. A new model for simulating contaminant spread via surface touch was developed and validated using the experimental data. The simulation revealed that surface contaminants were typically distributed non-uniformly. In scenarios with one or several localised contaminant sources, high-touch surfaces typically exhibited moderate contamination. A network with a high density of touches or multiple contaminant sources exhibited accelerated spread to a uniform contaminant distribution, with high-touch surfaces quickly approaching moderate concentrations. Therefore, surface touching could either contaminate or 'clean' surfaces. Undetectable or low pathogen concentrations on high-touch surfaces should not be interpreted as an absence of contaminated surfaces or of pathogen spread via surface touch.
Insights
High-touch surfaces may not always carry the most germs. This study shows that rarely touched surfaces can be heavily contaminated, challenging assumptions about infection transmission via touch. Understanding touch networks is key for disease prevention.
Area of Science:
- Environmental Microbiology
- Network Science
- Epidemiology
Background:
- Hand-touching contaminated surfaces is a known infection transmission route.
- The role of touch in pathogen spread is debated due to low loads on high-touch surfaces.
Purpose of the Study:
- To investigate surface contamination and pathogen spread in touch networks.
- To analyze the influence of touch behaviors and pathogen sources on contamination levels.
- To inform disease-prevention strategies.
Main Methods:
- Experimental observation of bacterial tracer particles in four settings.
- Development and validation of a novel model for simulating contaminant spread via surface touch.
- Analysis of touch network structures and contamination patterns.
Main Results:
- Most surfaces were rarely touched, but high-touch 'hubs' formed networks.
- Counterintuitively, rarely touched surfaces often showed the heaviest contamination.
- Contaminant distribution was non-uniform; high-touch surfaces showed moderate contamination with localized sources.
- High touch density or multiple sources led to accelerated, uniform contamination.
Conclusions:
- Low pathogen loads on high-touch surfaces do not rule out contamination or spread.
- Surface touching can both contaminate and 'clean' surfaces.
- Rethinking disease-prevention protocols based on complex touch network dynamics is necessary.
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