The principle is viral exposure over an extended period of time. In all these cases, people were exposed to the virus in the air for a prolonged period (hours). Even if they were 50 feet away (choir or call center), even a low dose of the virus in the air reaching them, over a sustained period, was enough to cause infection and in some cases, death.
Social distancing rules are really to protect you with brief exposures or outdoor exposures. In these situations there is not enough time to achieve the infectious viral load when you are standing 6 feet apart or where wind and the infinite outdoor space for viral dilution reduces viral load. The effects of sunlight, heat, and humidity on viral survival, all serve to minimize the risk to everyone when outside.
When assessing the risk of infection (via respiration) at the grocery store or mall, you need to consider the volume of the air space (very large), the number of people (restricted), how long people are spending in the store (workers - all day; customers - an hour). Taken together, for a person shopping: the low density, high air volume of the store, along with the restricted time you spend in the store, means that the opportunity to receive an infectious dose is low. But, for the store worker, the extended time they spend in the store provides a greater opportunity to receive the infectious dose and therefore the job becomes more risky.
Erin Bromage
A large part of the reason why this recent coronavirus outbreak has provoked harsh lockdown measures and caused unprecedented disruptions in society is simply the novelty of the virus. While many would like to dismiss the danger by comparing this virus with the flu, the analogy is moot because influenza has been around for millennia, and extensively researched since the dawn of modern medicine. In contrast, SARS‑CoV2 first infected humans late last year, so there is still a long list of unknowns about how the virus spreads and its effects on the human body, about the mortality rate and how long immunity lasts after recovery. Faced with many poorly quantifiable risks, the best course of action is to assume the worst; that is why I consider imposing strict lockdowns is necessary in the first stages.
To mention only a couple of the open questions about the health damages from a SARS‑CoV2 infection: heart failures, strokes and blood clots; an inflammatory disorder affecting children, who initially seemed less affected by the disease; larger prevalence of deaths among young people in the developing world, which may (or may not be) tied to preexisting conditions and poorer healthcare. Regarding transmission, a recent study suggests the virus may be able to enter the body through the eyes – another reason to doubt the effectiveness of face masks.
That being said, considering the information available so far, the article above analyses which activities and situations are riskier as countries consider ending the lockdowns and returning to a more normal state of affairs. Bottom line: more potential exposure means more risk of contracting the disease. Spending time outdoors is reasonably safe, especially if you avoid spending too much time with the same person, or in groups. Shopping is also reasonably safe, for the customer at least.
On the opposite end of the scale, workplaces and large indoor gatherings, from churches to restaurants and concerts, carry high risks of infection; even talking and breathing can produce dangerous numbers of viral particles over extended periods of time. I doubt masks and similar measures can protect people over long time spans – in fact, the medical profession was hard hit, despite their training in dealing with infectious diseases, despite protective gear. Even though Romania has a relatively low, and declining, number of cases, I am relieved that I can continue to work from home in coming months, and every company should consider extending work from home, if their operations allow it, or at least minimizing time spent in shared office spaces.
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