Background and Objective:
The spread of COVID-19 in indoor environments is a critical concern during the ongoing pandemic and mathematical modelling can provide insight into the transmission of SARS-CoV-2 in these settings. However, input factors used in these models have not been clearly described or analysed. The objective of this work was to retrieve and report the parameters related to the biological characteristics of SARS-CoV-2 and the physical parameters of the indoor environment that are used in the mathematical modelling of infectious disease transmission in indoor environments. This research was conducted within the framework of the national “OPtimal bEhavior iN paNdEmic ScenarioS” (OPENNESS) project, funded by Regione Lazio.

Methods:
We searched the PubMed database up to 31/11/2022 for English-language articles on quantitative risk assessment of indoor transmission of COVID-19. Articles addressing other infections or including outdoor-developing diseases were excluded.

Results:
The research generated 110 outputs, of which 2 studies were retained. One study employed a deterministic approach, while the other adopted a probabilistic mathematical method. The common parameters identified in the two studies were: the pathogen quanta emission rate, exposure to quanta concentration, number of quanta received by an exposed susceptible person, time-dependent particle number concentration, and deposition of particles in the host’s respiratory system. The deterministic model better predicts particle filtration and deposition into receptor respiratory systems, whereas the probabilistic model provides more accurate results in environmental conditions with less clearly specified parameters.

Conclusion:
The parameters identified in this review and their subsequent analysis lay the groundwork for future research on the mathematical modelling of SARS-CoV-2 indoor transmission. More research is needed to understand better the role of these parameters to validate and refine existing mathematical models, in order to inform public health decision-making and prevent COVID-19 from spreading in indoor environments.