![]() I also discuss recent controversies regarding the role of aerosols in transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the difficulties in evaluating the relative contribution of each mode to the transmission of respiratory viruses. In this Review, I will bring these discussions together to provide a broad overview of the transmissibility and modes of transmission of respiratory viruses, the approaches used to make these assessments, the viral, host and environmental determinants of transmission, and common NPIs for mitigating respiratory virus transmission, in the hope of illustrating the common approaches for studying respiratory virus transmission as well as the interconnection and differences between these discussions. These various aspects of transmissibility and transmission have been more comprehensively studied for influenza virus 4, 5, 6, 7, 10, 14, 17, 19 than for other respiratory viruses 9, 11, 12, 15, 16, 18. Previous reviews and commentaries discussed the transmissibility of influenza virus 4, 5 methods for studying transmission, including animal models 4, 5, 6, 7, human models 6, 8 and epidemiological studies 9 the mechanism and evidence for different modes of transmission 4, 6, 7, 9, 10, 11, 12 factors affecting transmission 4, 5, 11, 13 controversies regarding the relative importance of different modes of transmission 14, 15 pharmaceutical interventions 4 and NPIs 11, 16, 17, 18 for mitigating transmission 16, 17, 18, 19 and guidelines from public health agencies on infection prevention and control recommendations for respiratory viruses 9, 15. Therefore, understanding how to evaluate the transmissibility and evidence supporting different modes of transmission will aid in the control of respiratory virus transmission. The effectiveness and the suitability of a non-pharmaceutical intervention (NPI) to mitigate transmission depends substantially on the ease of transmission (transmissibility) and the mechanism of transmission (modes of transmission) specific to that virus, as these interventions can target some but not all potential modes of transmission. Until effective treatments or vaccines for COVID-19 are available, we have to rely heavily on population-based and individual-based public health measures to mitigate transmission. In addition, occasional pandemics cause extreme disruption to societies and economies as exemplified by the current COVID-19 pandemic. Together, they contribute to substantial morbidity 1, mortality 2 and concomitant economic losses 3 annually worldwide. Respiratory viruses belong to diverse virus families that differ in viral and genomic structures, populations susceptible to infection, disease severity, seasonality of circulation, transmissibility and modes of transmission. ![]() Respiratory virus infections often cannot be differentiated clinically. Human respiratory viruses include a broad range of viruses that infect cells of the respiratory tract, elicit respiratory and other symptoms, and are transmitted mainly by respiratory secretions of infected persons. ![]() Intervening against multiple modes of transmission should be more effective than acting on a single mode. ![]() Understanding the relative contribution of different modes to transmission is crucial to inform the effectiveness of non-pharmaceutical interventions in the population. Mechanistic evidence supports the efficacies of non-pharmaceutical interventions with regard to virus reduction however, more data are needed on their effectiveness in reducing transmission. Discussion on the particle size threshold between droplets and aerosols and the importance of aerosol transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus is ongoing. We know little about the relative contribution of each mode to the transmission of a particular virus in different settings, and how its variation affects transmissibility and transmission dynamics. Respiratory viruses can be transmitted via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets and (fine) aerosols. Transmissibility as estimated by the basic reproduction number ( R 0) or secondary attack rate is heterogeneous for the same virus. Belonging to diverse families, respiratory viruses differ in how easy they spread (transmissibility) and the mechanism (modes) of transmission. Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses worldwide, as seen in the COVID-19 pandemic.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |