Researchers, including those from the University of Edinburgh in the UK, have developed a new framework to gain fresh understanding of dispersion droplets of different sizes which are ejected as people breathe.
These findings have important implications for understanding the spread of airborne diseases like COVID-19.
Their study is published in the journal Physics of Fluids. In the study, researchers used mathematical formulae to determine the maximum range of small-, intermediate- and large-sized droplets. Their dispersion tests revealed the absence of intermediate-sized droplets.
Through a mathematical model, the researchers explored analytically to examine the dominant physics at play behind someone breathing.
As people breathe, they emit droplets of various sizes that don’t necessarily follow the airflow faithfully, said the study.
The current study provides a general framework to understand the droplet dispersion. The model provides formulas to predict when such droplets will have short ranges.
The model simplicity demonstrates that bimodality could actually be a property of the droplets themselves, and the group provides formulas to predict when such droplets will have short ranges.
The study shows there isn’t a linear relation between droplet size and displacement — with both small and large droplets travelling further than medium-sized ones.
The study suggests that personal protective equipments (PPEs) used by healthcare workers and clinicians are effective barriers to large droplets, but may be less effective for small ones.
Larger droplets are easily captured masks and face shields. But smaller droplets may penetrate some forms of PPE, so an extractor could help reduce the weakness in the current defense against COVID-19 and future pandemics,” one of the researchers said.
The researchers stressed the need for better understanding of the droplet behaviour. Understanding of the droplet behaviour will help inform the safety guidelines for aerosol-generating procedures, scientists argued.
The researchers are currently working on plans to manufacture an aerosol extractor device. They expect that this device will better protect clinicians during a wide range of aerosol-generating procedures.
In an analysis of 75,465 COVID-19 cases in China, 78-85% of clusters occurred within household settings, suggesting that transmission occurs during close and prolonged contact.
A study of the first patients in the Republic of Korea showed that 9 of 13 secondary cases occurred among household contacts. Outside of the household setting, those who had close physical contact, shared meals, or were in enclosed spaces for approximately one hour or more with symptomatic cases, such as in places of worship, gyms, or the workplace, were also at increased risk of infection.