The research places considerable emphasis upon physical distancing (what is sometimes called social distancing). This is seen to be far more effective, in the general sense, than social bubbles or the issuing of face masks. These other two measures will work, but they appear to be far more situation-dependent when the effectiveness of these actions is measured.
As to how this conclusion was reached, the scientists constructed a model designed to explore the relative effectiveness of the main measures that are being recommended by many governments and their scientific advisory boards.
To develop the model, the researchers came up with a concept that they called “event R.”
By this, the ‘event R’ represents the expected number of people who become infected with the betacoronavirus and develop COVID-19, stemming from one individual present in a given situation.
For the model to be robust, a series of variables needed to be considered. These variables were: transmission intensity, duration of exposure, the proximity of individuals and degree of mixing. This includes events classed as high-density and/or low-ventilation settings.
Of course there is another consideration that some people are also particularly vulnerable to the virus.
Event specific factors
With the context established, the next step was to consider the different recommended preventative actions and to see which of these was most effective at preventing viral transmission, according to different sets of circumstances.
To achieve this, voluminous data was inputted, with the data extracted from reports of outbreaks at different events. The types of events included were parties, meals, nightclubs, public transit and restaurants.
To these can be added setting types with cluster sizes above 50 or 100 cases, such as schools, sports venue, shopping malls, weddings, and conferences, each of which have several shared characteristics in terms of the way that people interact.
The most significant factor determining a given individual’s chances of becoming infected and developing COVID-19 was shown to be dependent upon the duration; that is the amount of time a person spends in a particular setting.
The different events were subsequently classed as either saturating (which means high transmission probability) or linear (which indicates low transmission probability).
Situations that fell under the high transmission category were bars, nightclubs and overcrowded workplaces. There is a particular concern with the indoor environment with the higher risk event settings.
In contrast, the low transmission category included such as settings public transit with masks, distancing in restaurants and outdoor activities.
With the different actions that can be taken, the findings indicated that physical distancing was by far the most effective tactic for reducing viral transmission, across all settings.
Workplaces
With other measures, the effectiveness of social bubbles was heavily dependent upon whether chances of transmission are high or low. That is, bubbles were less effective in a bar than in a workplace.
The important risk factors are:
Number of people,
The amount of mixing,
The levels of crowding,
The noise level,
Duration of the event.
However, even in workplaces there are risk, especially where the numbers of people is high. By social bubble, in the workplace context, this means using the same work area and restricting access to a smaller group of people. Open plan or shared office spaces present the greatest risk.
Hence, what is interesting is with workplaces is that maintaining a social bubble (that is working with the same small group) and working in the same location, are far more effective as reducing viral transmission. Whereas, working with a large and changing group of people, and working in an open plan, hot desking environment, increases the chances. This is even where masks are worn.
This supports data that shows SARS-CoV-2 having a propensity to cause large outbreaks among persons in office workplaces.
With masks, there is some effect but the effectiveness is reduced in highly populated, high transmission settings. These settings included parties, choirs, restaurant kitchens, crowded offices, nightclubs and bars.
This was because even where masks halve the transmission rates, these do not alter the probability significantly as this effect is counteracted by the high population and prolonged time in association with other people.
The continuing development of information is relation to the coronavirus continues to grow, but there remains much to learn about the epidemiological aspects.
Research paper
The research has been published in the journal Proceedings of the National Academy of Sciences. The science paper, which has undergoing peer review, is titled “Event-specific interventions to minimize COVID-19 transmission.”
Similar research conducted in Japan found several COVID-19 clusters associated with heavy breathing in close proximity, such as singing at karaoke parties, cheering at clubs, having conversations in bars, and exercising in gymnasiums. Another study from South Korea drew similar inferences from a fitness class.
Essential Science
This article forms part of Digital Journal’s long-running Essential Science series, where new research relating to wider science stories of interest are presented on a weekly basis.
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