THE AIRBORNE CONTAGIOUSNESS OF RESPIRATORY VIRUSES: A COMPARATIVE ANALYSIS AND IMPLICATIONS FOR MITIGATION

Background: The infectious emission rate is a critical input parameter for airborne contagion models, but data are limited due to reliance on estimates from chance superspreading events. A predictive estimation approach for the quanta emission rate (ERq) was recently proposed for SARS-CoV-2 using the droplet volume concentration of various expiratory activities. This study assesses the strength of the approach and uses novel predictive estimates of ERq to compare the contagiousness of respiratory pathogens. Methods: We applied the predictive approach to SARS-CoV-1, SARS-CoV-2, MERS, measles virus, adenovirus, rhinovirus, coxsackievirus, seasonal influenza virus and Mycobacterium tuberculosis (TB) and compared ERq estimates to values reported in literature. We calculated infection risk in a prototypical classroom and barracks to assess the relative ability of ventilation to mitigate airborne transmission. Results: Our median standing and speaking ERq estimate for SARS-CoV-2 (2.6 quanta hour (h)-1) is similar to active, untreated TB (3.1 h-1), higher than seasonal influenza (0.17 quanta h-1), and lower than measles virus (15 quanta h-1). We calculated event reproduction numbers above 1 for SARS-CoV-2, measles virus, and untreated TB in both the classroom and barracks for an activity level of standing and speaking at low, medium and high ventilation rates of 2.3, 6.6 and 14 liters per second per person, respectively. Conclusions: Our predictive ERq estimates are consistent with the range of values reported over decades of research. In congregate settings, current ventilation standards are unlikely to control the spread of viruses with upper quartile ERq values above 10 quanta h-1, such as SARS-CoV-2, indicating the need for additional control measures.