Multi-route respiratory infection: When a transmission route may dominate

Abstract

The exact transmission route of many respiratory infectious diseases remains a subject for debate to date. The relative contribution ratio of each transmission route is largely undetermined, which is affected by environmental conditions, human behaviour, the host and the microorganism. In this study, a detailed mathematical model is developed to investigate the relative contributions of different transmission routes to a multi-route transmitted respiratory infection. The following transmission routes are considered: long-range airborne transmission, short-range airborne transmission, direction inhalation of medium droplets or droplet nuclei, direct deposition of droplets of all sizes, direct and indirect contact route. It is illustrated that all transmission routes can dominate the total transmission risk under different scenarios. Influential parameters considered include the dose-response rate of different routes, droplet governing size that determines pathogen content in droplets, exposure distance, and pathogen dose transported to the hand of infector. Our multi-route transmission model provided a comprehensive but straightforward method to evaluate the probability of respiratory diseases transmission via different routes. It also established a basis for predicting the impact of individual-level intervention methods such as increasing close-contact distance and wearing protective masks.

Aerosol SARS-CoV-2 in hospitals and long-term care homes during the COVID-19 pandemic

“…[25] Moreover, inhalation of aerosols may be an important, even dominant transmission mode both within and beyond close contact. [8,23] We sampled indoor air for viral RNA and viable SARS-CoV-2 virus in a large number of rooms in a variety of settings and with a variety of room air change rates. We were careful to always sample two or more meters from COVID-19 patients, to ensure that we were detecting virus only at distances traditionally considered to be consistent with airborne transmission.…”

“…[8,21,22] Moreover, modelling studies show that even during close contact interactions, aerosols, rather than larger ballistic droplets, drive viral exposures, as droplets are relatively unlikely to land on a mucus membrane, compared to the higher likelihood of inhaling aerosols. [23] Research studies mainly rely on molecular detection of the SARS-CoV-2 genome to determine viral presence in aerosol samples. However, genome (RNA) presence alone is often seen as insufficient evidence that aerosol transmission risk is present, as it does not indicate the presence of viable virus.…”

Recent research on expiratory particles in respiratory viral infection and control strategies: A review

“… Sun and Zhai (2020) predicted the risk of droplet transmission infection by inserting a social distancing index. Gao et al. (2021) combined the Wells-Riley and dose-response model to examine the relative contributions of different transmission routes, including long-range airborne transmission, respiratory close contact transmission, and contact transmission.…”

Ventilation mode performance against airborne respiratory infections in small office spaces: limits and rational improvements for Covid-19

“…Different studies have produced estimates on V d with considerable discrepancies, given the uncertainty and complexity of the associated experimental measurements. A range from O(1) to O(10) nL h −1 for speaking was used in different studies [18,52], based on past experimental data [53,54]. Mikszewski et al [55] suggest the value of 4900 nL h −1 based on the recent measurements of Stadnytskyi et al [50] for loudly speaking.…”