As we find our way back to public life there are some facts about COVID-19 transmission that have becoming increasingly clear. It’s important to understand what factors increase risk and what things that are less concerning. Of course, if we wanted zero risk in life we’d never get on an airplane, drive the freeway or cross a street. Calculating risk is something we do, consciously or otherwise, every day of our life.
It appears that the biggest risk is being in an enclosed space with lots of other people for a prolonged period of time. As Erin Bromage (comparative immunologist and professor of biology at the University of Massachusetts Dartmouth) says: Successful Infection = Exposure to Virus x Time.
Bromage says, “Any environment that is enclosed, with poor air circulation and high density of people, spells trouble.” [His findings are also reported on CNN here]
In Bromage’s conclusion: “All these infection events were indoors, with people closely-spaced, with lots of talking, singing, or yelling. The main sources for infection are home, workplace, public transport, social gatherings, and restaurants. This accounts for 90% of all transmission events. In contrast, outbreaks spread from shopping appear to be responsible for a small percentage of traced infections.”
In a study of more than 7,300 cases in China, only one was connected to outdoor transmission. In that case, a man had a face-to-face conversation with a traveler who had just returned from Wuhan. Based on this math, the odds of contracting this indoors are 99.986% compared to being outside where the odds are about one-hundredth of one percent.
Couple this information with the recent report from Governor Andrew Cuomo’s findings from New York. The highest risk group was people who stayed home. 66% of hospitalized patients stayed home (retired, worked at home, unemployed). 4% used public transportation while 9% used their own car. It doesn’t make sense until you put it together with Bromage’s findings.
Now consider that in several U.S. States, 96% or more of prison inmates diagnosed with COVID-19 were asymptomatic – they were infected without getting ill. It’s certainly not because they’re social distancing or because they’re on a good diet in a low stress environment – in fact, it’s the opposite. Do they have stronger immune systems resulting from higher exposures to a pathogenic environment? Who knows. But our immune system, like muscles and pretty much every other biological system, gets increasingly weak if it goes unchallenged. Could our obsessive sanitizing and hiding at home be creating immunological atrophy?
Bromage states: “Importantly, of the countries performing contact tracing properly, only a single outbreak has been reported from an outdoor environment (less than 0.3% of traced infections).”
Even the risk of being indoors can be reduced when there is less talking and less exertion (heavy breathing) going on. The findings from a South Korean fitness center report on the CDC website are telling. Exercise participants were in a 650 square foot room where classes were held for Zumba (dance exercise), yoga and Pilates. They concluded: “The moist, warm atmosphere in a sports facility coupled with turbulent air flow generated by intense physical exercise can cause more dense transmission of isolated droplets. Classes from which secondary COVID-19 cases were identified included 5 to 22 students in a room approximately 60 square meters (650 square feet) during 50 minutes of intense exercise. We did not identify cases among classes with fewer than 5 participants in the same space. Of note, instructor C taught Pilates and yoga for classes of 7–8 students in the same facility at the same time as instructor B but none of her students tested positive for the virus. We hypothesize that the lower intensity of Pilates and yoga did not cause the same transmission effects as those of the more intense fitness dance classes.”
The logical conclusion to all of this is that being outdoors (as we are at our dojo) and having a reasonable distance between participants appears to pose a significantly lower health risk than being at home and is safer by orders of magnitude than simply going to a grocery store.
Here a great video showing how being outdoors is radically safer than being indoors in pretty much every situation.