Editor’s note: This commentary is by Dr. Turner Osler, a career academic trauma surgeon at the University of Vermont Medical Center turned research epidemiologist, and Alan Hedge, emeritus professor of Design & Environmental Analysis at Cornell University.
Covid-19 has changed almost every aspect of our lives, so our intense interest in this virus is understandable. But while it’s important to know one’s enemy, Sun Tzu’s thinking in “The Art of War” is more nuanced. He observes: “If you know the enemy and know yourself, you need not fear the result of a hundred battles.”
It’s our belief that we’ve lost this balance in dealing with the coronavirus. Yes, our growing understanding of the virus has allowed improved medical treatments, but actually ending the pandemic will require that we better understand ourselves.
Remarkably, a single very human trait has elevated Covid-19 from simply another virus to a global pandemic. Our need to be with others, and especially to be with them indoors, has left us uniquely vulnerable. We are modern “cave creatures,” spending more than 90% of our lives indoors, and our viral foe mindlessly exploits this habit.
Crucially, it is almost impossible to transmit Covid-19 out-of-doors. In one study of over 7,000 transmission events, only two happened out-of-doors. Li and colleagues concluded: “Sharing indoor space is a major SARS-CoV-2 infection risk.” Inverting Li’s point, we might ask: What is it about the out-of-doors that stops viral spread? And can we bring it indoors?
There is a lot of air outside, so simply being outdoors immediately dilutes any viral cloud. Within moments, viral concentrations fall below the infective dose. Additionally, sunlight kills the coronavirus within minutes. So, moving our meetups out-of-doors will make us all safer and help end the pandemic sooner.
We’ve long known this, actually. In the early 20th century, tuberculosis was the pandemic, a different pathogen in a different era, but, like Covid-19, spread by respiratory droplets. Schools across the United States remained open by simply keeping their large, expansive windows open all winter long or holding classes outside. Yes, it was chilly, but disease transmission ended.
But could we actually bring the out-of-doors indoors? That is, can we re-create the safety of outside, indoors?
Framed this way, the current pandemic isn’t a viral problem, or even a human interaction problem; it becomes an engineering problem. And engineering problems should have engineering solutions: higher air flow to recapitulate the air volume out of doors, and ultraviolet lights to reproduce the effects of sunlight.
We’ve recognized the importance of ventilation for over 200 years but unfortunately, with the invention of air-conditioning, we closed windows, sealed buildings, and reduced ventilation rates to save energy, changes that have greatly advantaged the Covid-19 virus. Covid-19 will require us to increase our ventilation standards, but no ventilation system can compete with the outdoors. Fortunately, simply opening a window, perhaps with the addition of a fan, immediately brings almost all the benefits of being outside indoors.
Although sunlight rapidly denatures Covid-19, little direct sunlight penetrates our living spaces. Currently available workarounds such as germicidal ultraviolet-C light (GUV) are not common in the United States, but in other countries GUV has been used to control another airborne invader, tuberculosis. Fortunately, GUV is highly effective against Covid-19, so this mature technology is readily available.
Upgrading our current buildings to provide clean “out-of-doors” air quality won’t likely happen soon enough to help with the current pandemic. Other workspace modifications — such as barriers between office workstations or greater distances between desks in schools — may be effective against Covid-19 carried on droplets that stay aloft for minutes and travel several feet.
Unfortunately, the virus can also be carried on much smaller microdroplets (aerosols), which stay aloft for hours and fill rooms. Worse, unlike SARS and MERS, Covid-19 can remain infectious for up to 16 hours in indoor air.
Because no strategy can make an indoor workplace safe, we must also continue universal masking, social distancing and hand hygiene.
Simply being out-of-doors provides the greatest protection from Covid-19 currently available. But even outside, a direct Covid-19-laden sneeze will instantly create an infective plume of virus, so masks remain critical even when outside. But we can almost be comfortable in each other’s presence when out-of-doors, well distanced and personally protected.
Although we cannot totally eliminate Covid-19, it turns out this isn’t necessary; we need only reduce the transmission to an R0 of less than 1. At that point, the viral pandemic will recede. We can’t change the behavior of the virus, but by adjusting our own behavior and redesigning our environments, we can make progress: Choosing to interact with others less frequently in smaller groups and at greater distances, combined with personal protective measures, and especially meeting up out-of-doors whenever possible. These simple steps taken together will curtail our Covid-19 pandemic.
In the longer term, redesigning the spaces in which we live and work to have air quality closer to that out-of-doors will help protect us from this pandemic, and pandemics yet to come. We can think of indoor air quality as a long-term investment that will pay big dividends down the road if we are wise enough to make it now.
