̽��ֱ�� of Cambridge - Epaminondas Mastorakos

Taking Cambridge global

skbf2 — Fri, 01 Dec 2023 11:54:25 +0000

In 2013, Cambridge opened its first-ever overseas research centre, the Cambridge Centre for Advanced Research and Education in Singapore (CARES).?Over the past decade, CARES has grown into a thriving community of 150 staff and researchers, working with partners to achieve scientific breakthroughs with a global impact.

Two-metre COVID-19 rule is ��arbitrary measurement�� of safety

sc604 — Tue, 23 Nov 2021 15:54:09 +0000

A team of engineers from the ̽��ֱ�� of Cambridge used computer modelling to quantify how droplets spread when people cough. They found that in the absence of masks, a person with COVID-19 can infect another person at a two-metre distance, even when outdoors.

̽��ֱ��team also found that individual coughs vary widely, and that the ��safe�� distance could have been set at anywhere between one to three or more metres, depending on the risk tolerance of a given public health authority.

̽��ֱ��results, published in the journal Physics of Fluids, suggest that social distancing is not an effective mitigation measure on its own, and underline the continued importance of vaccination, ventilation and masks as we head into the winter months in the northern hemisphere.

Despite the focus on hand-washing and surface cleaning in the early days of the pandemic, it��s been clear for nearly two years that COVID-19 spreads through airborne transmission. Infected people can spread the virus through coughing, speaking or even breathing, when they expel larger droplets that eventually settle or smaller aerosols that may float in the air.

��I remember hearing lots about how COVID-19 was spreading via door handles in early 2020, and I thought to myself if that were the case, then the virus must leave an infected person and land on the surface or disperse in the air through fluid mechanical processes,�� said Professor Epaminondas Mastorakos from Cambridge��s Department of Engineering, who led the research.

Mastorakos is an expert in fluid mechanics: the way that fluids, including exhaled breath, behave in different environments. Over the course of the pandemic, he and his colleagues have developed various models for how COVID-19 spreads.

��One part of the way that this disease spreads is virology: how much virus you have in your body, how many viral particles you expel when you speak or cough,�� said first author Dr Shrey Trivedi, also from the Department of Engineering. ��But another part of it is fluid mechanics: what happens to the droplets once they��re expelled, which is where we come in. As fluid mechanics specialists, we��re like the bridge from virology of the emitter to the virology of the receiver and we can help with risk assessment.��

In the current study, the Cambridge researchers set out to ��measure�� this bridge through a series of simulations. For example, if a person coughed and emitted a thousand droplets, how many would reach another person in the same room, and how large would these droplets be, as a function of time and space?

̽��ֱ��simulations used refined computational models solving the equations for turbulent flow, together with detailed descriptions of droplet motion and evaporation.

̽��ֱ��researchers found that there isn��t a sharp cut-off once the droplets spread beyond two metres. When a person coughs and isn��t wearing a mask, most of the larger droplets will fall on nearby surfaces. However, smaller droplets, suspended in the air, can quickly and easily spread well beyond two metres. How far and how quickly these aerosols spread will depend on the quality of ventilation in the room.

In addition to the variables surrounding mask-wearing and ventilation, there is also a high degree of variability in individual coughs. ��Each time we cough, we may emit a different amount of liquid, so if a person is infected with COVID-19, they could be emitting lots of virus particles or very few, and because of the turbulence they spread differently for every cough,�� said Trivedi.

��Even if I expel the same number of droplets every time I cough, because the flow is turbulent, there are fluctuations,�� said Mastorakos. ��If I��m coughing, fluctuations in velocity, temperature and humidity mean that the amount someone gets at the two-metre mark can be very different each time.��

̽��ֱ��researchers say that while the two-metre rule is an effective and easy-to-remember message for the public, it isn��t a mark of safety, given the large number of variables associated with an airborne virus. Vaccination, ventilation and masks �C while not 100% effective �C are vital for containing the virus.

��We��re all desperate to see the back of this pandemic, but we strongly recommend that people keep wearing masks in indoor spaces such as offices, classrooms and shops,�� said Mastorakos. ��There��s no good reason to expose yourself to this risk as long as the virus is with us.��

̽��ֱ��research team are continuing this research with similar simulations for spaces such as lecture rooms that can help assess the risk as people spend more time indoors.

Mastorakos is a Fellow of Fitzwilliam College, Cambridge. ̽��ֱ��research was supported in part by the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

Reference:
Shrey Trivedi et al. ��Estimates of the stochasticity of droplet dispersion by a cough.�� Physics of Fluids (2021). DOI: 10.1063/5.0070528

A new study has shown that the airborne transmission of COVID-19 is highly random and suggests that the two-metre rule was a number chosen from a risk ��continuum��, rather than any concrete measurement of safety.

We strongly recommend that people keep wearing masks in indoor spaces - there��s no good reason to expose yourself to this risk as long as the virus is with us

Epaminondas Mastorakos

How droplets spread in a cough

Pedro de Oliveira

Visualisation of droplets from a cough

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ? ̽��ֱ�� of Cambridge and licensors/contributors as identified.? All rights reserved. We make our image and video content available in a number of ways �C as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Free online tool calculates risk of COVID-19 transmission in poorly-ventilated spaces

sc604 — Wed, 20 Jan 2021 00:55:09 +0000

̽��ֱ��results, reported in the journal Proceedings of the Royal Society A, show that social distancing measures alone do not provide adequate protection from the virus, and further emphasise the vital importance of ventilation and face masks in order to slow the spread of COVID-19.

̽��ֱ��researchers, from the ̽��ֱ�� of Cambridge and Imperial College London, used mathematical models to show how SARS-CoV-2 �C the virus which causes COVID-19 �C spreads in different indoor spaces, depending on the size, occupancy, ventilation and whether masks are being worn. These models are also the basis of a free online tool, Airborne.cam, which helps users understand how ventilation and other measures affect the risk of indoor transmission, and how that risk changes over time.

̽��ֱ��researchers found that when two people are in a poorly-ventilated space and neither is wearing a mask, prolonged talking is far more likely to spread the virus than a short cough. When speaking, we exhale smaller droplets, or aerosols, which spread easily around a room, and accumulate if ventilation is not adequate. In contrast, coughing expels more large droplets, which are more likely to settle on surfaces after they are emitted.

It only takes a matter of seconds for aerosols to spread over two metres when masks are not worn, implying that physical distancing in the absence of ventilation is not sufficient to provide safety for long exposure times. When masks of any kind are worn however, they slow the breath��s momentum and filter a portion of the exhaled droplets, in turn reducing the amount of virus in aerosols that can spread through the space.

̽��ֱ��scientific consensus is that the vast majority of COVID-19 cases are spread through indoor transmission �C whether via aerosols or droplets. And as was predicted in the summer and autumn, now that winter has arrived in the northern hemisphere and people are spending more time indoors, there has been a corresponding rise in the number of COVID-19 cases.

��Our knowledge of airborne transmission of SARS-CoV-2 has evolved at an incredible pace, when you consider that it��s been just a year since the virus was identified,�� said Dr Pedro de Oliveira from Cambridge��s Department of Engineering, and the paper��s first author. ��There are different ways to approach this problem. In our work, we consider the wide range of respiratory droplets humans exhale to demonstrate different scenarios of airborne viral transmission �C the first being the quick spread of small infectious droplets over several metres in a matter of a few seconds, which can happen both indoors and outdoors. Then, we show how these small droplets can accumulate in indoor spaces in the long term, and how this can be mitigated with adequate ventilation.��

̽��ֱ��researchers used mathematical models to calculate the amount of virus contained in exhaled particles, and to determine how these evaporate and settle on surfaces. In addition, they used characteristics of the virus, such as its decay rate and viral load in infected individuals, to estimate the risk of transmission in an indoor setting due to normal speech or a short cough by an infectious person. For instance, they show that the infection risk after speaking for one hour in a typical lecture room was high, but the risk could be decreased significantly with adequate ventilation.

Based on their models, the researchers have now built Airborne.cam, a free, open-source tool which can be used by those managing public spaces, such as shops, workplaces and classrooms, in order to determine whether ventilation is adequate. ̽��ֱ��tool is already in use in several academic departments at the ̽��ֱ�� of Cambridge. ̽��ֱ��tool is now a requirement for any higher-risk spaces at the ̽��ֱ��, enabling departments to easily identify hazards and control-measure changes needed to ensure aerosols are not allowed to become a risk to health.

�� ̽��ֱ��tool can help people use fluid mechanics to make better choices, and adapt their day-to-day activities and surroundings in order to suppress risk, both for themselves and for others,�� said co-author Savvas Gkantonas, who led the development of the app with Dr de Oliveira.

��We��re looking at all sides of aerosol and droplet transmission to understand, for example, the fluid mechanics involved in coughing and speaking,�� said senior author Professor Epaminondas Mastorakos, also from the Department of Engineering. �� ̽��ֱ��role of turbulence and how it affects which droplets settle by gravity and which remain afloat in the air is, in particular, not well understood. We hope these and other new results will be implemented as safety factors in the app as we continue to investigate.��

̽��ֱ��continuing development of Airborne.cam, which will soon be available for mobile platforms, is supported in part by Cambridge Enterprise and Churchill College.

Reference:
P?M?de Oliveira et al. ��Evolution of spray and aerosol from respiratory releases: theoretical estimates for insight on viral transmission.�� Proceedings of the Royal Society A (2021). DOI: 10.1098/rspa.2020.0584

̽��ֱ��vital role of ventilation in the spread of COVID-19 has been quantified by researchers, who have found that in poorly-ventilated spaces, the virus can spread further than two metres in seconds, and is far more likely to spread through prolonged talking than through coughing.

̽��ֱ��tool can help people use fluid mechanics to make better choices, and adapt their day-to-day activities and surroundings in order to suppress risk, both for themselves and for others

Savvas Gkantonas

Gauthier DELECROIX - ��

Five senses series - Taste 1/2

Yes

Licence type:

Attribution