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Practical Indicators for Risk of Airborne Transmission in Shared Indoor Environments and Their Application to
Z Peng1, A L Pineda Rojas2, E Kropff3
1Dept. of Chemistry and CIRES, University of Colorado, Boulder, Colorado 80309, United States.
Abstract:
Some infectious diseases, including COVID-19, can undergo airborne transmission. This may happen at close proximity, but as time indoors increases, infections can occur in shared room air despite distancing. We propose two indicators of infection risk for this situation, that is, relative risk parameter (Hr) and risk parameter (H). They combine the key factors that control airborne disease transmission indoors: virus-containing aerosol generation rate, breathing flow rate, masking and its quality, ventilation and aerosol-removal rates, number of occupants, and duration of exposure. COVID-19 outbreaks show a clear trend that is consistent with airborne infection and enable recommendations to minimize transmission risk. Transmission in typical prepandemic indoor spaces is highly sensitive to mitigation efforts. Previous outbreaks of measles, influenza, and tuberculosis were also assessed. Measles outbreaks occur at much lower risk parameter values than COVID-19, while tuberculosis outbreaks are observed at higher risk parameter values. Because both diseases are accepted as airborne, the fact that COVID-19 is less contagious than measles does not rule out airborne transmission. It is important that future outbreak reports include information on masking, ventilation and aerosol-removal rates, number of occupants, and duration of exposure, to investigate airborne transmission.
Insights
Airborne transmission of infectious diseases like COVID-19 indoors is quantified by new risk parameters (Hr and H). These factors help assess and minimize infection risks in shared spaces.
Area of Science:
- Environmental health
- Infectious disease epidemiology
- Aerosol science
Background:
- Airborne transmission of infectious diseases, including COVID-19, poses significant risks in indoor environments.
- Infection can occur in shared room air over time, even with physical distancing measures in place.
Purpose of the Study:
- To propose and define two new indicators of infection risk for airborne transmission indoors: the relative risk parameter (Hr) and the risk parameter (H).
- To combine key factors influencing indoor airborne disease transmission into quantifiable risk parameters.
Main Methods:
- Developed risk parameters (Hr and H) integrating virus aerosol generation, breathing rates, masking effectiveness, ventilation, occupant numbers, and exposure duration.
- Analyzed COVID-19 outbreaks and compared them with historical data for measles, influenza, and tuberculosis.
Main Results:
- COVID-19 outbreaks demonstrate trends consistent with airborne transmission, allowing for risk-mitigation recommendations.
- Transmission risk is highly sensitive to mitigation efforts in typical indoor settings.
- Measles outbreaks occurred at lower risk parameter values than COVID-19, while tuberculosis outbreaks occurred at higher values.
Conclusions:
- The proposed risk parameters provide a framework for assessing and managing airborne infection risks indoors.
- The findings support the airborne transmission of COVID-19 and highlight the importance of mitigation strategies.
- Future outbreak reports should include detailed information on environmental and exposure factors to facilitate airborne transmission studies.
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