What’s the best way to boost the economy? Invest in high-voltage transmission lines



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Peter Martin, Crawford School of Public Policy, Australian National University

When, in the midst of the pandemic, the Economic Society of Australia invited 150 of Australia’s keenest young thinkers to come up with “brief, specific and actionable” proposals to improve the economy, amid scores of ideas about improving job matching, changing the tax system, providing non-repayable loans to businesses and accelerating telehealth, two proposals stood out.

They were actually the same proposal, arrived at independently by two groups of “hackers” in the society’s annual (this time virtual) “hackathon”.

I was one of the judges.

The mentors who helped test and guide the proposals were some of the leading names in economics, among them Jeff Borland, John Quiggin, Gigi Foster, Deborah Cobb-Clark, Peter Abelson and John Hewson.

The proposal is to fast track the 15 or more projects already identified by the Australian Energy Market Operator as essential to meet the electricity grid’s transmission needs over the next 20 years.

Starting them immediately, when business investment is weak and there’s a need for jobs and governments can borrow at rates close to zero, will bring forward all of the benefits of being able to bring ultra-cheap power from the places it will be made to the places it will be needed as expensive fossil-fuel generators bow out or are out competed.




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Judges Alison Booth, Jeremy Thorpe and I noted that policy hacks were the most useful where neither the market nor the government was getting the job done.

The proposal would help ensure renewables can connect to the grid, something “neither the market nor the government is managing to do quickly”.

A few weeks later Labor leader Anthony Albanese used his budget reply speech to propose the same thing – a Rewiring the Nation Corporation to turn the projects identified in the Energy Market Operator’s integrated system plan into reality.

Here is what is proposed in the winners’ own words:

Accelerating priority transmission projects

Nick Vernon, Agrata Verma, Bella Hancock

Investment in new renewable generators in Australia sank 40% in 2019. A major factor holding them back is grid access. The best locations for wind and sun often have poor access to the cables that transport electricity to consumers.

Our near-term recommendation is to guarantee Project EnergyConnect, a 900-kilometre cable between NSW and South Australia due to begin construction next year. The network operators got approval in January, but there is now uncertainty over whether they will get the funding.




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We propose that the two state governments agree to cover the shortfall between approved revenues and realised costs (up to a pre-determined limit) to ensure construction starts on time in 2021.

Medium-term, we recommend the Australian Energy Regulator conduct the regulatory investment test and revenue adjustment processes for all priority projects in parallel to condense approval timelines and that the Commonwealth and state governments underwrite priority projects’ early works.

This would allow service providers to commission new transmission lines sooner after regulatory approval.


AEMO Integrated System Plan

The case for fast tracking transmission

Patrick Sweeney, Sam Edge, Elke Taylor, Jacob Keillor, Timothy Fong

Currently valued at A$20 billion, the Australian transmission network was designed for a centralised 20th century power mix and suffers from aging infrastructure.

The $6 billion upgrade we propose would have as its centrepiece 15 projects the Energy Market Operator has already identified as essential.

Fast-tracking these projects has the potential to generate 100,000 jobs, to bring about strong private investment in low-carbon power production, and to place downward pressure on wholesale power prices, producing $11 billion in benefits.

A national taskforce consisting of the department of energy and the market operator would oversee a project of a similar size to the Snowy Mountains scheme, which itself created more than 100,000 jobs during its lifecycle.




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The government would procure the funds by issuing bonds, with recent rates indicating the yield payable will be less than the rate of inflation.

Firms that tendered for the work would be evaluated on their capacity to upscale production to meet milestones and on their plans to generate long-term, sustainable employment.The Conversation

Peter Martin, Visiting Fellow, Crawford School of Public Policy, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Behind Victoria’s decision to open primary schools to all students: report shows COVID transmission is rare



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Fiona Russell, University of Melbourne; Edward Kim Mulholland, Murdoch Children’s Research Institute; Kathleen Ryan, Murdoch Children’s Research Institute; Kathryn Snow, University of Melbourne; Margie Danchin, Murdoch Children’s Research Institute, and Sharon Goldfeld, Murdoch Children’s Research Institute

At the weekend, Victorian Premier Dan Andrews announced all the state’s primary school kids would return to school for Term 4. This is an update from the previously planned staggered return to primary school, which would begin only with students in the early years — prep (first year) to Year 2.

The change was informed by our analysis of Victorian health and education department data on all cases and contacts linked to outbreaks at schools and early childhood education and care services (childcare and preschool).

We included data between January 25 (the date of the first known case in Victoria) and August 31.

Our analysis found children younger than 13 seem to transmit the virus less than teenagers and adults. In instances where the first case in a school was a child under 13, a subsequent outbreak (two or more cases) was uncommon. This finding played a key role in helping make the decision for primary school children to return to school.

Here is what else we found.

1. Outbreaks in childcare and schools are driven by community transmission

Infections linked to childcare, preschools and schools peaked when community transmission was highest in July, and declined in August. In addition, they were most common in the geographical areas where community transmission was also high.

This suggests infections in childcare, preschools and schools are driven primarily by transmission in the broader community. Controlling community transmission is key to preventing school outbreaks.

2. School infections are much lower than in the community

There were 1,635 infections linked with childcare, preschools and schools out of a total of 19,109 cases in Victoria (between January 25 and August 31).

Of 1 million students enrolled in all Victorian schools, 337 may have acquired the virus through outbreaks at school.




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Of 139 staff and 373 students who may have acquired infection through outbreaks at childcare, preschools or schools, eight (four staff and four students) were admitted to hospital, and all recovered.

The infections in childcare, preschools and schools were very rarely linked to infections in the elderly, who are the most vulnerable to COVID-19.

3. Most infections in schools and childcare centres were well contained

Of all the outbreaks in Victorian childcare centres, preschools and schools, 66% involved only a single infection in a staff member or student and did not progress to an outbreak. And 91% involved fewer than ten cases.

Testing, tracing and isolation within 48 hours of a notification is the most important strategy to prevent an outbreak.

The majority of infections in childcare, preschools and schools were well contained with existing controls and rapid closure (within two days), contact tracing and cleaning.




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4. Households are the main source of infection, not schools

The investigations of cases identified in schools suggest child-to-child transmission in schools is uncommon, and not the primary cause of infection in children. Household transmission has been consistently found to be the most common source of infection for children.

Closing schools should be a last resort

Based on our findings and a review of the international literature, we recommend prioritising childcare centres, preschools and schools to reopen and stay open to guarantee equitable learning environments — and to lessen the effects of school closures.

Children do transmit the virus and outbreaks can occur. But based on the international literature, this mostly happens when there are high rates of community transmission and a lack of adherence to mitigation measures (such as social distancing) at the school or childcare centre.

Childcare centres, preschools and schools play a critical role not only in providing education, but also offering additional support for vulnerable students.

With childcare centres and schools being closed, along with the additional economic and psychological stress on families, family conflict and violence has increased. This has led to many children and young people feeling unsafe and left behind in their education and suffering mental-health conditions.

Closing all schools as part of large-scale restrictions should be a last resort. This is especially the case for childcare centres, preschools and primary schools, as children in these age groups are less likely to transmit the virus, and be associated with an outbreak.

Now that community transmission in Victoria is so low, it’s time for all kids to go back to school.




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The authors would like to thank their advisory committee from the Department of Education and Training and the Department of Health and Human Services. They would also like to thank outbreak epidemiologists at the DHHS and medical students Alastair Weng, Angela Zhu, Anthea Tsatsaronis, Benjamin Watson, Julian Loo Yong Kee, Natalie Commins, Nicholas Wu, Renee Cocks, Timothy O’Hare, and research assistant Kanwal Saleem, and Belle Overmars.The Conversation

Fiona Russell, Principal research fellow, University of Melbourne; Edward Kim Mulholland, Professor, Murdoch Children’s Research Institute; Kathleen Ryan, Research Fellow, Asia-Pacific Health, Infection and Immunity Theme, Murdoch Children’s Research Institute; Kathryn Snow, Epidemiologist, University of Melbourne; Margie Danchin, Associate Professor, University of Melbourne, Murdoch Children’s Research Institute, and Sharon Goldfeld, Director, Center for Community Child Health Royal Children’s Hospital; Professor, Department of Paediatrics, University of Melbourne; Theme Director Population Health, Murdoch Children’s Research Institute

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This video shows just how easily COVID-19 could spread when people sing together



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C Raina MacIntyre, UNSW; Abrar Ahmad Chughtai, UNSW; Charitha de Silva, UNSW; Con Doolan, UNSW; Prateek Bahl, UNSW, and Shovon Bhattacharjee, UNSW

Production of the reality TV show The Masked Singer was shut down last month after several crew members were infected with COVID-19.

It’s one of several examples of COVID-19 transmission associated with singing around the world since March, prompting some jurisdictions to ban group singing altogether.

In New South Wales, for example, choral singing is banned and there are no-singing rules at weddings and nightclubs.

Now our new study, which included filming droplets and aerosols emitted when someone sings, shows how singing might be an infection risk. This is especially if many people sing together, in a poorly ventilated room.

What we did and what we found

We took high-speed video of a person singing a major scale, as do-re-mi-fa-so-la-ti-do (seen below, without audio). We then tracked the emissions of droplets and aerosols.

We found certain notes, such as “do” and “fa”, generated more aerosols than others. We also found the direction of emissions changed with different consonants.

Infection control guidelines assume respiratory droplets settle rapidly within one to two metres of the person emitting them.

However, most droplets we observed appeared not to settle rapidly, and tended to follow the ambient airflow.

Therefore, without adequate ventilation, these droplets may persist in aerosol clouds.

These observations may partially explain the higher infection rates of COVID-19 during group singing, even when people singing appear well.

Our findings are based on one person singing and individuals may generate aerosols differently. However, our findings apply to singing in any groups, such as churches, schools and social gatherings, all of which are vulnerable to outbreaks of COVID-19.




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What is it with choirs?

We’ve known since March of the potential for group singing to transmit SARS-CoV-2, the virus that causes COVID-19. In this well-documented US example, 87% of 61 people who attended one 2.5 hour choir practice became infected, with two deaths. One singer had mild symptoms during rehearsal.

Now our research adds to the growing body of research looking at the transmission risk of singing and the role aerosols might play.

We know social distancing is effective in reducing the risk of spread during normal social interactions. However, singing in a group and in closed, poorly ventilated environments may generate more aerosols than speaking.

When we sing, we vocalise louder and often hold notes for longer. This, together with many singers close together in confined spaces for an hour or more, create conditions that may increase the spread of SARS-CoV-2.

When researchers analysed results from the US choir example, they estimated the infection risk could have been halved with a shorter choir practice.




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We tend to think of only coughs or sneezes as the primary source of generating aerosols. But even breathing generates aerosols, albeit at lower concentrations.

In fact, we breathe and speak much more than we cough or sneeze. So the cumulative aerosol exposure for a group of people singing and talking, without coughing or sneezing, in a closed environment may be higher than from a single cough.

How can we sing together, safely?

We’ve seen online choirs as a safe alternative to traditional ones.

Singing from your couch is one safe way to continue singing in a group.

Other options for safer group singing now and in the future include:

  • singing outside or in a well-ventilated room with large open windows as this is likely to dissipate aerosols and further reduce the risk

  • physical distancing of at least two metres while singing

  • short performances to minimise exposure

  • humming rather than singing during rehearsals, because we show consonants (such as “do”) generate the most aerosols

  • singing softly (and using amplifiers) as this is likely to emit fewer aerosols

  • using rapid test kits, if available, which would allow singers to be screened before performing

  • assessing risk factors for individual singers based on age, chronic diseases and other risk factors for COVID-19. It is more important people at high risk of complications from COVID-19 avoid group singing while there is community transmission.

Some people recommend wearing face shields while group singing. But these allow you to breathe in aerosols through the gap underneath, which may be even more likely with the powerful inhalations during singing.

No one measure alone will be enough to mitigate the risk. We need multiple measures used together — physical distancing, shorter performances, open windows, outdoor venues, softer singing and risk-based screening — to allow safer group singing.The Conversation

C Raina MacIntyre, Professor of Global Biosecurity, NHMRC Principal Research Fellow, Head, Biosecurity Program, Kirby Institute, UNSW; Abrar Ahmad Chughtai, Epidemiologist, UNSW; Charitha de Silva, Lecturer, UNSW; Con Doolan, Professor, School of Mechanical and Manufacturing Engineering, UNSW; Prateek Bahl, PhD Candidate, School of Mechanical and Manufacturing Engineering, UNSW, and Shovon Bhattacharjee, PhD Candidate, The Kirby Institute, UNSW

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Children might play a bigger role in COVID transmission than first thought. Schools must prepare



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Zoë Hyde, University of Western Australia

Over the weekend, the World Health Organisation made an announcement you might have missed.

It recommended children aged 12 years and older should wear masks, and that masks should be considered for those aged 6-11 years. The German Society for Virology went further, recommending masks be worn by all children attending school.

This seems at odds with what we assumed about kids and COVID-19 at the start of the pandemic. Indeed, one positive in this pandemic so far has been that children who contract the virus typically experience mild illness. Most children don’t require hospitalisation and very few die from the disease. However, some children can develop a severe inflammatory syndrome similar to Kawasaki disease, although this is thankfully rare.

This generally mild picture has contributed to cases in children being overlooked. But emerging evidence suggests children might play a bigger role in transmission than originally thought. They may be equally as infectious as adults based on the amount of viral genetic material found in swabs, and we have seen large school clusters emerge in Australia and around the world.

How likely are children to be infected?

Working out how susceptible children are has been difficult. Pre-emptive school closures occurred in many countries, removing opportunities for the virus to circulate in younger age groups. Children have also missed out on testing because they typically have mild symptoms. In Australia, testing criteria were initially very restrictive. People had to have a fever or a cough to be tested, which children don’t always have. This hindered our ability to detect cases in children, and created a perception children weren’t commonly infected.

One way to address this issue is through antibody testing, which can detect evidence of past infection. A study of over 60,000 people in Spain found 3.4% of children and teenagers had antibodies to the virus, compared with 4.4% to 6.0% of adults. But Spain’s schools were also closed, which likely reduced children’s exposure.

Another method is to look at what happens to people living in the same household as a known case. The results of these studies are mixed. Some have suggested a lower risk for children, while others have suggested children and adults are at equal risk.

Children might have some protection compared to adults, because they have less of the enzyme which the virus uses to enter the body. So, given the same short exposure, a child might be less likely to be infected than an adult. But prolonged contact probably makes any such advantage moot.

The way in which children and adults interact in the household might explain the differences seen in some studies. This is supported by a new study conducted by the Centers for Disease Control and Prevention. Children and partners of a known case were more likely to be infected than other people living in the same house. This suggests the amount of close, prolonged contact may ultimately be the deciding factor.

How often do children transmit the virus?

Several studies show children and adults have similar amounts of viral RNA in their nose and throat. This suggests children and adults are equally infectious, although it’s possible children transmit the virus slightly less often than adults in practice. Because children are physically smaller and generally have more mild symptoms, they might release less of the virus.

In Italy, researchers looked at what happened to people who’d been in contact with infected children, and found the contacts of children were more likely to be infected than the contacts of adults with the virus.

Teenagers are of course closer to adults, and it’s possible younger children might be less likely to transmit the virus than older children. However, reports of outbreaks in childcare centres and primary schools suggest there’s still some risk.

What have we seen in schools?

Large clusters have been reported in schools around the world, most notably in Israel. There, an outbreak in a high school affected at least 153 students, 25 staff members, and 87 others. Interestingly, that particular outbreak coincided with an extreme heatwave where students were granted an exemption from having to wear face masks, and air conditioning was used continuously.

At first glance, the Australian experience seems to suggest a small role for children in transmission. A study of COVID-19 in educational settings in New South Wales in the first half of the year found limited evidence of transmission, although a large outbreak was noted to have occurred in a childcare centre.

This might seem reassuring, but it’s important to remember the majority of cases in Australia were acquired overseas at the time of the study, and there was limited community transmission. Also, schools switched to distance learning during the study, after which school attendance dropped to 5%. This suggests school safety is dependent on the level of community transmission.

Additionally, we shouldn’t be reassured by examples where children have not transmitted the virus to others. Approximately 80% of secondary COVID-19 cases are generated by only 10% of people. There are also many examples where adults haven’t transmitted the virus.

As community transmission has grown in Victoria, so has the significance of school clusters. The Al-Taqwa College outbreak remains one of Australia’s largest clusters. Importantly, the outbreak there has been linked to other clusters in Melbourne, including a major outbreak in the city’s public housing towers.

Close schools when community transmission is high

This evidence means we need to take a precautionary approach. When community transmission is low, face-to-face teaching is probably low-risk. But schools should switch to distance learning during periods of sustained community transmission. If we fail to address the risk of school outbreaks, they can spread into the wider community.

While most children won’t become severely ill if they contract the virus, the same cannot be said for their adult family members or their teachers. In the US, 40% of teachers have risk factors for severe COVID-19, as do 28.6 million adults living with school-aged children.

Children walk to school with masks
In the US, 40% of teachers have risk factors for severe COVID-19, as do 28.6 million adults living with school-aged children.
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Recent recommendations on mask-wearing by older and younger children mirror risk-reduction guidelines for schools developed by the Harvard T. H. Chan School of Public Health. These guidelines stress the importance of face masks, improving ventilation, and the regular disinfection of shared surfaces.

The changing landscape

As the virus has spread more widely, the demographic profile of cases has changed. The virus is no longer confined to adult travellers and their contacts, and children are now commonly infected. In Germany, the proportion of children in the number of new infections is now consistent with their share of the total population.

While children are thankfully much less likely to experience severe illness than adults, we must consider who children have contact with and how they can contribute to community transmission. Unless we do, we won’t succeed in controlling the pandemic.The Conversation

Zoë Hyde, Senior Research Officer, University of Western Australia

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Workplace transmissions: a predictable result of the class divide in worker rights


Kantha Dayaram, Curtin University; John Burgess, RMIT University, and Scott Fitzgerald, Curtin University

How to stop sick people going to work?

That’s a question the Victorian government has been grappling with since it became clear about 80% of new COVID-19 infections in the state’s second-wave outbreak were from workplace transmissions.




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After official visits to 3,000 people meant to be self-isolating found more than 800 not at home, the government instituted the largest on-the-spot fine in the state’s history – A$4,957 for defying a stay-at-home order (and up to $20,000 for going to work knowing you have COVID-19).

Along with the big sticks, there have been carrots. The Victorian government, the Fair Work Commission and the federal government have all weighed in to provide financial support to workers who lack paid sick leave.

But these measures have been a belated band aid to a problem that should have been entirely predictable. It’s the consequence of a deepening class divide in work in which hundreds of thousands of essential workers in high-risk industries are poorly paid and lack job security, guaranteed hours or sick-leave entitlements.

Aged care workers

Aged-care homes (linked to more than 2,000) cases and meat-processing facilities (linked to about 870 cases) show the predicament of “flexible employment” for workers.

In the aged care sector, about 90% of carers are female, 32% born overseas, 78% permanent part-time and 10% casual or contract, according to the 2016 National Aged Care Workforce Census and Survey. Seven in ten are employed as personal care attendants. Of those, almost 60% work 16–34 hours a week, with a median wage of A$689. About 30% want to work more hours, and 9% work more than one job.

An underemployed workforce is advantageous to employers. As the Bankwest Curtin Economics Centre’s 2018 report on developing sustainable careers for aged care workers noted:

Underemployment offers organisations a buffer of additional hours that can be accessed when there are staff shortages. The regularity and predictability of hours is a challenge for workers, though, in terms of their lack of employment and income stability.

It might now be noted it also makes it problematic for them to turn down shifts, to stay home if they feel unwell, or to seek out a coronavirus test lest a positive result forces them to self-quarantine.

Meat processing workers

In red-meat-processing facilities, about 20% of the processing workforce is casual, according to a 2015 report by the Australian Meat Processor Corporation. These workers “can be terminated on any given day part-way through a shift”.

The rest of the workforce is barely more secure, with 80% employed as “daily hires”. This means their jobs technically terminate at the end of a shift. They can be sacked with just one day’s notice.

Media reports have highlighted the predicament for workers without paid sick leave. At the Golden Farms Turosi poultry processing site in Geelong, for example, media reported that workers told to self-isolate after a COVID-19 outbreak in July were then directed to return to work early to clean the premises.

The United Workers Union said the company expected its workers “to dip into their own entitlements or, for casuals, be left with nothing at all” during the stand-down. Glenn Myhre, a Golden Farms worker for 34 years, put it like this:

This is leaving a lot of people very insecure. Casuals and people with no entitlements are going to be left in a really tight spot.




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Fair Work Commission decisions

It should not be surprising that those with insecure incomes and jobs would risk going to work when they do feel unwell.

Yet official appreciation of this has been slow.

In April the Fair Work Commission, Australia’s industrial relations arbiter, approved changes to more than 100 awards to provide two weeks’ pandemic leave for all employees, including casual workers. But the leave was unpaid.

On July 8 it deferred a union application for paid pandemic leave to health workers (to be paid by employers).

The commission accepted expert evidence that “at a high level of generality, workers in the health and social care sectors are at a higher risk of infection by COVID-19 (and other infectious diseases)”.

It also acknowledged the “very real risk” that employees with no paid leave entitlements “may not report any COVID-19-like symptoms or contact with someone suspected of having COVID-19 out of concern that they will suffer significant financial detriment”.

However, the commission ruled, “the elevated potential risk to health and care workers of actual or suspected exposure to infection has not manifested itself in actuality”.

Three weeks later, on July 27, as the disaster in Victoria’s aged care facilities unfolded, the commission granted paid pandemic leave to casual aged care workers.

Covering all workers

Ensuring paid pandemic leave for all workers has taken longer.

In June the Victorian government introduced a one-off A$1,500 “hardship payment” for workers left with no income if ordered to self-quarantine. It did not, however, cover lost income from self-isolating while awaiting the result of a COVID-19 test.

On August 3, the day after Victorian Premier Daniel Andrews declared a state of disaster and a stage 4 lockdown for Melbourne, the federal government announced a $1,500 “disaster payment” for all Victorians without paid leave entitlements who are ordered to self-isolate.

Then, after a joint call from the Australian Council of Trade Unions and the Business Council of Australia for a national paid pandemic leave, the federal government agreed to extend the disaster payment to all states and territories.

A festering class divide

The failure to anticipate this problem is one of the greatest flaws in Australia’s response to the pandemic.

The belated payments are a tacit acknowledgement of a systemic problem. It is one that needs more than a temporary band-aid.

For a society that prides itself on egalitarianism, the mounting evidence that vulnerable workers have borne the brunt of health and financial impacts calls for broad reform of an industrial relations system that has allowed a class divide in working conditions to fester.




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To paraphrase the sociologist C. Wright Mills, the pandemic should motivate us to finally acknowledge as a public issue what has perhaps been too easily dismissed as the private troubles of individual workers.The Conversation

Kantha Dayaram, Associate Professor, School of Management, Curtin University; John Burgess, Professor of Human Resource Management, RMIT University, and Scott Fitzgerald, Senior Lecturer, School of Management, Curtin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Is the airborne route a major source of coronavirus transmission?



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Hassan Vally, La Trobe University

As the world continues to grapple with the coronavirus pandemic, one question that keeps coming up is whether COVID-19 can be transmitted through the air.

In fact, 239 scientists in 32 countries have written an open letter to the World Health Organisation (WHO) arguing there is mounting evidence the airborne route plays a role in the transmission of COVID-19.

Like a lot of issues to do with the pandemic, what seems to be a relatively straightforward question is deceptively complex. We actually don’t know the answer for sure.

Why do we need to understand the modes of transmission?

Understanding how COVID-19 is transmitted from one person to the next enables us to design effective public health interventions to minimise the risk of transmission.

For instance, we’re advised to keep 1.5 metres away from others because there’s consensus one of the main ways the virus spreads is via large droplets.

These “large” droplets are usually greater than 5 micrometres in size and are propelled from an infected person’s nose or mouth in their mucus and saliva when they sneeze, cough or talk.

Thanks to gravity, these large droplets don’t generally travel far before landing. If you position yourself more than 1.5 metres from someone who is infected, the expectation is you’ll be clear of the droplets’ path.




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Similarly, understanding these large droplets can land on surfaces and that the virus can survive on these surfaces means we know we need to wash our hands to avoid transferring the virus to our mouth, nose or eyes.

Until now, the WHO has maintained these large droplets are the major source of COVID-19 transmission. But the authors of the open letter suggest they are underplaying the role of airborne transmission.

Airborne transmission and COVID-19

In its simplest interpretation, airborne transmission refers to the ability of a virus to be spread by droplets small enough to be suspended in the air. These droplets are less than 5 micrometres in size and generally called aerosols.

Whereas large droplets can only travel short distances, these smaller droplets, in theory, can be spread further, or can linger in a room even after an infected person has left.

COVID-19 spreads when an infectious person emits tiny virus-containing droplets.
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Evidence supporting the notion that transmission of COVID-19 can occur via the airborne route takes several forms.

First, laboratory studies have demonstrated that SARS-CoV-2, the coronavirus that causes COVID-19, can be aerosolised, and can survive for up to four hours in this form.

Second, genetic material from SARS-CoV-2 has been detected in aerosols sampled at hospitals, including two hospitals in Wuhan, the Chinese city from which the pandemic emerged. But it’s important to note the presence of this genetic material doesn’t necessarily mean the virus is infectious in this form.




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Perhaps the strongest evidence, however, comes through the various case reports of superspreading events. These are situations in which many people appear to have been infected with coronavirus in the absence of close contact.

One notable early example was from a choir practice in the United States where almost 50 people were infected even though they maintained physical distance. Two died.

Another example is an outbreak in Guangzhou, China, where ten people from three families contracted COVID-19 after dining in a restaurant. Non-infected people were not in close contact with any infected person, but those who became infected were in the direct line of one air conditioning unit.

The study of this outbreak is not yet peer-reviewed but is part of the evidence the authors of the open letter draw on.

What are the implications of airborne transmission?

Airborne transmission of this novel coronavirus is potentially a worry, because if it occurs often, it means the virus may be commonly transmitted in the absence of close contact.

It also raises the possibility the virus may travel on air currents, and even be transmitted through air conditioning.

This means social distancing may not always be effective, and in particular, crowded indoor areas with poor ventilation pose a major threat.

Good ventilation could lower the risk of airborne transmission in indoor spaces.
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So where does this leave us?

The key question is not whether airborne transmission is theoretically possible; it certainly is. But rather, how significant is its role in the transmission of COVID-19?

If, for example, most transmission of SARS-CoV-2 happens via large droplets and the airborne route plays a role only occasionally, this has very different implications to a scenario where the airborne route is a significant mode of transmission.

Reassuringly, the interventions that have been implemented to limit spread of the virus, such as social distancing, have been largely successful so far in most of Australia. This suggests even if the virus can be spread by the airborne route, it’s not likely to be a major route of transmission.

Given what we know, the dilemma is whether to employ the precautionary principle and assume the airborne route plays an important role in disease transmission — and adjust infection control measures accordingly. This may take the form of encouraging wider use of masks and looking at increasing ventilation in enclosed spaces.

The other approach is to wait for more definitive evidence before changing the public health advice.

We will await with interest the WHO’s response to the open letter.




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The Conversation


Hassan Vally, Associate Professor, La Trobe University

This article is republished from The Conversation under a Creative Commons license. Read the original article.