For the majority of teachers and pupils, September will mark the first time they have attended school full-time since March, when the coronavirus lockdown began. Understandably, many will be nervous.
Away from debates about masks and protocols if someone in the school community tests positive, one of the most common worries will be hygiene: has that desk been cleaned down properly? Could the novel coronavirus be lurking in a pupil’s well-thumbed Dickens novel? Is it safe to walk up the stairs following the whole of class 9B?
Scientists can shed some light here: laboratory tests and field research have revealed which areas of a school might present the highest risks and how schools might mitigate those risks.
Coronavirus: Reopening schools safely
First, we need to understand droplets.
“When we speak, cough, sneeze and breath, we produce droplets that are of respirable/inhalable size [small droplets known as aerosol] and also much larger droplets that are even larger than the diameter of a human hair,” explains Jonathan Reid, professor of physical chemistry at the University of Bristol and an expert on aerosols.
The larger droplets fall quickly to the ground in a few seconds and could contaminate surfaces, offering “an indirect, but important way viruses are transmitted”, he adds.
Then there’s the risk of being directly exposed to larger droplets when someone sneezes or coughs if they are standing nearby, hence physical distancing guidance.
How to wear a face mask correctly
But there’s also a question over whether infection can take place via those small aerosol particles, which can remain suspended in the air for many minutes or even hours.
Given the difficulties in persuading primary school children, in particular, to distance from each other or from staff - perhaps more like impossibilities - the question could be a pressing one for schools.
Aerosol risk
One study, led by researchers from the US National Institute of Allergy and Infectious Diseases and published in a brief summary in the New England Journal of Medicine, says its results suggest that novel coronavirus transmission via aerosol and surfaces is “plausible”. Researchers found that “the virus can remain viable and infectious in aerosols for hours and on surfaces up to days”.
However, that research took place in a lab rather than real-life conditions; plenty of scientists think that the evidence on aerosol transmission is inconclusive at present. Reid is attempting to offer more definitive answers in a current study.
Ventilation is key
So on the current evidence, which areas of a school does Reid think might present the highest risk of infection?
“I would say anywhere that is unventilated or poorly ventilated, has a high throughput of people or where there can be contaminated surfaces or poor hygiene - so, for example, toilets,” he replies.
Lawrence Young, a virologist and a professor of molecular oncology at the University of Warwick, agrees: “Any indoor environment where there is poor ventilation is a risk for transmission. This would be exacerbated by having many individuals walking through an area - like a corridor or communal area. Social distancing in these areas is essential.”
Indeed, for Peter Collignon, an infectious diseases physician and microbiologist at Canberra Hospital and a professor at the Australian National University, it’s people rather than surfaces that we should be worrying about. He says that in a school the key means of potential virus transmission are teachers and parents, making “staffrooms and indoor meetings with parents” the riskiest areas.
He suggests limiting staffroom numbers to allow for social distancing and trying to be “outdoors more than indoors” in general.
Which surfaces are worst?
When it comes to viruses’ survival on surfaces, one authority is Bill Keevil, professor of environmental healthcare at the University of Southampton. His research has found that the coronavirus that causes the common cold, which he describes as “structurally almost identical to the new virus”, survived “at least five days on stainless steel, glass, plastics, ceramics”.
Similarly, the New England Journal of Medicine study found that the novel coronavirus was detected on plastic after 72 hours - but could not be found on cardboard after 24 hours.
So perhaps plastic desktops should be a focus for cleaning, with book covers less of a concern for long-lasting infection risk.
Should school staff be worried if they touch a door handle and forget to wash their hands afterwards?
“I would be, because I’m a microbiologist,” Professor Keevil replies, none too reassuringly. “Humans, we’re very tactile. We continually touch our faces, eyes, nose and mouth - anything from 15 to 30 times an hour.”
The highest-risk surfaces would be the obvious touch ones, he adds: “door handles and push plates, stair rails” and “toilet areas, particularly for younger children”.
Conflicting accounts
However, other researchers point to reasons not to cower in fear before every surface.
“Don’t panic,” says Collignon of the risks of touching a door handle. “Being close to someone inside with a cough for over 15 minutes is very much higher risk. But use hand sanitisers before touching your face or eating.”
In response to the 72-hour figure for the virus’ survival on plastic found by the New England Journal of Medicine study, Johns Hopkins University professor of cell biology Carolyn Machamer has noted that just 0.1 per cent of the virus material remains after that time, making infection unlikely.
She told the Johns Hopkins website that people are “more likely to catch the infection through the air if you are next to someone infected than off of a surface. Cleaning surfaces with disinfectant or soap is very effective because once the oily surface coat of the virus is disabled, there is no way the virus can infect a host cell.”
And perhaps there is another solution for schools on surfaces. Keevil has been studying the antimicrobial effects of copper for 20 years, with his research on other coronaviruses finding that they were “inactivated in minutes” when they came into contact with such surfaces.
A fair copper
If you enjoy the idea of the coronavirus taking a beating, then savour Keevil’s description of how macho-sounding copper ions “can punch holes in the cell membrane” of a bacterium or virus, allowing the ions to “flood into the cell, inhibit the respiration of bacteria then destroy DNA and RNA [ribonucleic acid] in both bacteria and viruses, which means there is no chance of mutation and resistance”.
He highlights a Greek study that found reduced rates of respiratory infections in schools where copper alloys were used to cover or replace surfaces such as stair rails.
Surfaces can be coated in copper, Keevil says, “so rather than have to completely rekit schools in solid copper alloys…as an interim, you can go in and cover them”.
Aside from such potential innovations, the best options for schools at present, then, seem to lie in ventilation, physical distancing (or attempts at it) and, of course, routine and frequent cleaning.
So is there any one place more infectious than another?
Think of it more as a sliding scale: the busier or more frequently used the surface or school site, the more enclosed and poorly ventilated that space is, the higher the risk. This is not the time to be helping a fellow teacher clean out their cupboard.
John Morgan is a freelance journalist
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