Event-specific interventions to minimize COVID-19 transmission

Abstract

COVID-19 is a global pandemic with over 25 million cases worldwide. Currently, treatments are limited, and there is no approved vaccine. Interventions such as handwashing, masks, social distancing, and “social bubbles” are used to limit community transmission, but it is challenging to choose the best interventions for a given activity. Here, we provide a quantitative framework to determine which interventions are likely to have the most impact in which settings. We introduce the concept of “event R,” the expected number of new infections due to the presence of a single infectious individual at an event. We obtain a fundamental relationship between event R and four parameters: transmission intensity, duration of exposure, the proximity of individuals, and the degree of mixing. We use reports of small outbreaks to establish event R and transmission intensity in a range of settings. We identify principles that guide whether physical distancing, masks and other barriers to transmission, or social bubbles will be most effective. We outline how this information can be obtained and used to reopen economies with principled measures to reduce COVID-19 transmission.

Ventilation procedures to minimize the airborne transmission of viruses at schools

“…The virus transmission potential due to the airborne route was assessed in terms of event reproduction number (R event ) which is the expected number of new infections arising from a single infectious individual at a specific event [39] (e.g. a single school day).…”

COVID-19’s unfortunate events in schools: mitigating classroom clusters in the context of variable transmission

“…We note that our maximum value of β (when both the environment and the infectiousness of the index case are most conducive to transmission) is 0.018 transmissions per contact per hour. This is considerably smaller than the estimates of index β for widely-reported outbreaks in adults [38], by up to a factor of 30 for some events. Table 1 lists the parameter values used in our simulations and provides supporting citations.…”

“…Finally, steps should be taken to control the environment's contribution to the variation in transmission rates (and therefore to cluster sizes). Indoor, crowded, loud, poorly ventilated environments with singing, eating and dining are recognized to be comparatively high risk [36,38]. However, data could now be gathered prospectively with a focus on schools: when there are exposures in classroom settings, these could be linked to data on the room size, ventilation, whether windows were open, numbers of students in the class and classroom organization, and then further linked to follow-up on cluster size.…”

The Airborne Contagiousness of Respiratory Viruses: A Comparative Analysis and Implications for Mitigation

“…To quantify the ability of ventilation to mitigate the risk of airborne transmission, we calculated the individual risk (R) of an exposed person [6] and event reproduction numbers (R event ) for a typical classroom studied by Wells [11] and for a military barracks studied by Couch et al [12]. R event is defined as the expected number of new infections arising from a single infectious individual at an event [13]. We performed the calculations using low, medium, and high ventilation rates of 2.3 liters per second per person (L s -1 p -1 ), 6.6 L s -1 p -1 , and 14 L s -1 p -1 , respectively, and assuming one infectious occupant and a fully susceptible population.…”