“...systematic knowledge of the physical or material world gained through observation and experimentation”…”knowledge, as of facts or principles; knowledge gained by systematic study”.
Add to that this excerpt from Miriam-Webster.com : “..the state of knowing : knowledge as distinguished from ignorance or misunderstanding”. This covers the territory for me.
“Science” is not static. A body of knowledge about a new human virus changes with time as we get to know more and more about it. What we do about it is sometimes based on misleading and incomplete information. Combined with wacky conspiracy theories and unproven assertions of fact, the public response to the presence of the virus can veer into irrationality.
Early on in the pandemic, medical authorities recommended that masks should be worn by front-line medical workers, but were not necessary for average citizens without symptoms to contain the spread of the disease. This was based partly on a shortage of masks for medical workers who were most at risk of coming into contact with people who were contagious and falling ill because of it. As the shortage of masks eased and more studies came out about the value of masks in controlling previous epidemics, the recommendation changed to encourage the use of masks by everyone who was in a situation where strict social distancing could not be observed, and, finally, everyone out in public should wear a mask because many people can be contagious with the virus before they experience symptoms. Many others transmit the virus without ever knowing they have it.
For some, this seemed like a betrayal. People we are supposed to trust told us one thing and then recommended the exact opposite a few weeks later. “Science” does not offer certainty or necessarily comfort for people who are confused and fearful. But scientific knowledge, even as it changes, usually gives us the best chance to protect ourselves and our fellow citizens - in other words, to do the right thing.
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“News” about Covid-19 that is more than two weeks old may be out of date. But this article, "The Risks - Know Them - Avoid Them", 5/6/2020, that appeared as a blog post by Erin Bromage, an Associate Professor of Biology at the University of Massachusetts, Dartmouth, functions as a little instruction manual for understanding the virus that causes Covid-19 and what we can do to avoid infection and prevent its spread. This is especially relevant as states remove restrictions on activities that have helped to contain the virus.
Here at two things from Bromage’s blog post to keep in mind when you read the article:
“As states reopen, and we give the virus more fuel, all bets are off. I understand the reasons for reopening the economy, but I've said before, if you don't solve the biology, the economy won't recover. “ [emphasis added]
and
“Remember the formula: Successful Infection = Exposure to Virus x Time”
Highlights from “The Risks - Know Them - Avoid Them”
Based on infection dose of other Corona viruses, “Infection could occur, through 1000 infectious viral particles you receive in one breath or from one eye-rub, or 100 viral particles inhaled with each breath over 10 breaths, or 10 viral particles with 100 breaths. Each of these situations can lead to an infection.”
Sources of Infection
"A Bathroom: Bathrooms have a lot of high touch surfaces, door handles, faucets, stall doors. So fomite [objects or materials that are likely to carry infection] transfer risk in this environment can be high. We still do not know whether a person releases infectious material in feces or just fragmented virus, but we do know that toilet flushing does aerosolize many droplets. Treat public bathrooms with extra caution (surface and air), until we know more about the risk...."
“A Cough: A single cough releases about 3,000 droplets and droplets travels at 50 miles per hour. Most droplets are large, and fall quickly (gravity), but many do stay in the air and can travel across a room in a few seconds."
"A Sneeze: A single sneeze releases about 30,000 droplets, with droplets traveling at up to 200 miles per hour. Most droplets are small and travel great distances (easily across a room)."
"A breath: A single breath releases 50 - 5000 droplets. Most of these droplets are low velocity and fall to the ground quickly. There are even fewer droplets released through nose-breathing. Importantly, due to the lack of exhalation force with a breath, viral particles from the lower respiratory areas are not expelled."
"Speaking increases the release of respiratory droplets about 10 fold; ~200 virus particles per minute. Again, assuming every virus is inhaled, it would take ~5 minutes of speaking face-to-face to receive the required dose.
Who is contagious?
“Symptomatic people are not the only way the virus is shed. We know that at least 44% of all infections--and the majority of community-acquired transmissions--occur from people without any symptoms (asymptomatic or pre-symptomatic people). You can be shedding the virus into the environment for up to 5 days before symptoms begin.”
“The amount of virus released from an infected person changes over the course of infection and it is also different from person-to-person. Viral load generally builds up to the point where the person becomes symptomatic. So just prior to symptoms showing, you are releasing the most virus into the environment. Interestingly, the data shows that just 20% of infected people are responsible for 99% of viral load that could potentially be released into the environment.”
Where are you most likely to contract the virus?
“We know most people get infected in their own home. A household member contracts the virus in the community and brings it into the house where sustained contact between household members leads to infection."...
“But where are people contracting the infection in the community? I regularly hear people worrying about grocery stores, bike rides, inconsiderate runners who are not wearing masks.... are these places of concern? Well, not really. Let me explain….”
Bromage gives excellent explanations with references to relevant studies of outbreaks that show where an invidual is most at risk to contract the virus.
“The reason to highlight these different outbreaks is to show you the commonality of outbreaks of COVID-19. 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.”
…”Basically, as the work closures are loosened, and we start to venture out more, possibly even resuming in-office activities, you need to look at your environment and make judgments. How many people are here, how much airflow is there around me, and how long will I be in this environment. If you are in an open floorplan office, you really need to critically assess the risk (volume, people, and airflow). If you are in a job that requires face-to-face talking or even worse, yelling, you need to assess the risk. “
Most importantly, “… if you don't solve the biology, the economy won't recover. “
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Read “The Risks - Know Them - Avoid Them” by Erin Bromage to see all the graphics accompanying the article, references to studies, and information about the author.
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