Reopening: Know and Avoid the Risks

Musical chairs goes viral

By DJ Rippert

The Bromage Broadcast. Erin Bromage is a professor of biology and a blogger. She will tell you that she’s not an expert epidemiologist but she recently wrote a blog entry that proves she is an eloquent writer when it comes to explaining the physics of Coronavirus to the layman. As Virginia reopens after the lockdown people will have to make personal decisions about what activities to undertake and what activities to avoid. Ms. Bromage’s plain English explanations make a good starting point for making such decisions.

1,000 Particles. The Coronavirus comes to its victims in the form of virus particles. A virus particle is a structure that has evolved to transfer nucleic acid from one cell to another. However, as Ms Bromage explains, different viruses need to transfer different numbers of virus particles to a potential host in order to create an infectious dose. Studies of Coronaviruses other than SARS-CoV2 indicate that relatively few virus particles are required to create an infectious dose. Based on this, experts put the number of virus particles required to form an infectious dose of SARAS-CoV2 as low as 1,000. Obviously, these virus particles need to somehow get to you to infect you.

Breathing. Human respiration creates aerosolized droplets of liquid. These are the vehicles used by virus particles to travel from an infected person to the next potential host. Breathing creates between 50 and 5,000 droplets per breath. The good news is that breathing creates low velocity droplets that fall to the ground quickly. Even better, the amount of viral material expelled through breathing is quite low – 20 to 33 infectious viral particles per minute. It should be noted that this figure is an extrapolation from influenza since the exact numbers for SARS-CoV2 are still unknown. Using 20 viral particles per minute and assuming they all make it to you … you’ll receive an infectious dose of SARS-CoV2 from being in close proximity to a breathing person in 50 minutes (20 X 50 = 1,000). However, it is highly unlikely that all the emitted viral particles will make it to you. Walking past somebody in a grocery store might be fine while sitting next to somebody on a cross country flight might not.

Speaking. Talking ups the generation of virus particles by 10-fold over breathing. In the unlikely event that all of the virus particles are transferred, you could be infected by your talkative neighbor in 5 minutes. When going through the checkout line at the grocery store you may not want to shoot the breeze with the cashier.

Coughing. A cough puts out 3,000 droplets traveling at 50 mph. The droplets are relatively heavy and most fall to the floor but the velocity is sufficient to get some of the viral particles across a room in a few minutes. Coughs (and sneezes) really blow out the viral particles with up to 200,000,000 of the nasties on the 3,000 droplets from a single cough.

Sneezing. Sneezing is the MIRV of viral attack. A sneeze produces 30,000 droplets (10 times more than a cough) traveling at 200 mph (4X faster than a cough). A single sneeze, like a single cough, can transmit 200,000,000 viral particles. If you’re in a room and you hear the “ah” part of an “ah choo” … close your eyes, hold your breath, put your head down and hit the nearest emergency exit like John Riggins in his prime. More seriously, by the time you hear somebody sneeze it’s probably too late. Sneeze droplets are small and will easily travel across a room.

Whatever way the wind blows. Bromage provides two excellent examples of real-world infections, one in a restaurant (see diagram at top of article) and the other in a call center. Both indicate that the odds of being infected change with the airflow in an enclosed space. Unsurprisingly, it’s better to be upwind. Surprisingly, virtually unnoticeable routine air flow turbulence can turn the tables for those seeking upwind advantage. So much for a standard six feet of separation.

Bottom line. Professor Bromage’s article is the first I’ve seen to put COVID-19 infection into somewhat probabilistic terms. It certainly explains why 66% of people recently admitted to New York hospitals were infected while sheltering at home. It doesn’t take a non-sheltering housemate long to pass along thousands of virus particles while explaining what a lousy day they had at work. It also doesn’t take a lot of deep thinking to tell your hair stylist to work quickly and quietly.

There are currently no comments highlighted.

29 responses to “Reopening: Know and Avoid the Risks

  1. Got an opinion about bathrooms?

    that’s the first place many folks go when dining or bar …right?

    • Probably way cleaner now than they were before all this, given the additional attention. Wash up going in, wash up going out. Hand hygiene and masks still the first line of defense. Don’t use that rolling towel thingee. 🙂 But that was true before.

      What was recognized weeks ago remains the case: Few exposed get sick, few who get sick get very sick, and most recover unless 65+ and/or suffering from a pre-existing condition (or three.) Much worse than flu (which many refuse to see) but no where near as dangerous as many other infectious diseases (which the the other side refuses to see.)

    • Yeah…. wash your hands pre and post handling of your junk…. just like the old joke… know the difference between a biologist and a chemist? A chemist washes his hands before peeing. And keep that paper towel to turn on/off the water, flush, and push the door open.

  2. AND THIS:

    • If the person coming out of the bathroom has been coughing….hold it. Hey, no question, I’m not heading into a restaurant to sit inside soon. Maybe on the patio. Maybe not. Takeout on my patio works fine. But in general most people are not going to behave with the same level of caution. People screaming about the law bore me, but human nature is a truly powerful force. Most have had it with this.

    • No Larry. That stuff causes a wicked headache.

  3. Got my hair cut this afternoon! I had a mask on; he had a mask on. I was in and out in about 10 minutes. Neither of us coughed or sneezed.

    Thanks for the post, Don. That was informative and in language I could understand, along with your nice sense of humor.

  4. Congrats! I bought a clipper… and so I’m going to hold out a little longer.

    It sounds like even DJ is going to be circumspect about bars… and such…

  5. What about doorknob licking? Window licking? Boot licking? Is the VP at risk in this last one?

    BTW, the President has been taking hydroxychloroquine. Dear god, is he insane?

  6. I believe that restaurant diagram is the result of contact tracing in South Korea. The seat marked A1 was the infected person at a birthday party. The other people at table A were friends an relatives. The dates are when each became sick.

  7. There is some confusion over “family”. Some folks think that if you are “family” even if you live in different houses that you don’t have to socially distance. Anyone else heard that?

  8. Now that I’ve read the article DJ linked, its major implication is for schools. A classroom full of energetic kids for hours on end…..

    • K-12 or higher ed or both?

      I’ve yet to see any state-level rules for either.

    • James Wyatt Whitehead V

      Mr. Haner is right. As we speak public school leaders are formulating plans for the fall. I can only hope that what is decided upon will best serve the interests of students. I can assure you of this. If we start the fall with distance learning we will lose over half of the students for the year. We must find a way to get students safely back into brick and mortar schools. Reminds me of Apollo 13. Failure is not an option.

      • James – have you heard of any guidelines or rules in place for schools to follow to be able to open up?

        Do you think there should be uniform guidelines that apply to all schools or each school/school system decide on it’s own?

        • James Wyatt Whitehead V

          Mr. Larry I don’t believe they will make up their minds any time soon. The options include one like TMT suggested. Another is to start with distance learning to wait and see how the fall develops for 2nd/3rd wave of the virus. Should this be a uniform policy? It probably will end up that way. I prefer letting the school boards instruct superintendents on what course to pursue.

      • How about splitting a class into two and attending three days per week? Monday through Wednesday and Thursday through Saturday. Or Monday, Wednesday, Friday/Tuesday, Thursday, Saturday. Fewer desks. Nothing left in desks.

        • There are “ideas” – but as far as I can tell, no settled guidelines and each “idea” actually has operational and budgetary consequences.

          Most teachers I know will say that if you were to cut the school week in half for students that many would fall behind and not stay on grade.

          Is there a way to keep all kids on grade with no additional money required?

          Can anyone imagine the school systems in Virginia going to their respect BOS who have just lost significant tax revenues and telling them they need more money than last year?

          Whatever “solution” is decided upon is not going to satisfy everyone and I would expect challenges – both political and legal.

        • James Wyatt Whitehead V

          This might work. It would likely be supplemented with distance learning tools such as Edmentum and the plan would also include a virtual component too such as the Google Classroom and Google Meet. Additional costs are certain. It is expensive to operate schools on a Saturday too. I personally like the idea of Saturday School for next year. One third of this current school year was essentially lost. Next year will begin with reteaching content not covered this spring. So more class time essential. Teachers are going to have to accept that they will work more days next year and likely at a lower salary.

        • We can all agree that the time going forward is going to be difficult for everyone. Teachers, along with countless others, may have to do more with less. My brother teaches in New Hampshire. He’s expecting this.

          Most school systems are trying to keep teachers on the payroll and at the same salary. That’s a much better situation than many other people face.

  9. Don’t forget the improper wear of masks and gloves, that’s another wonderful virus vector.

    • James Wyatt Whitehead V

      Don’t forget the bathrooms, locker rooms, showers, lunch line, tables in the cafe, playgrounds, athletics, dances, plays, and on and on and on. Gee whiz I am so fortunate my retirement parachute is opening in just 3 weeks. It is going to be very tough for school teachers next year.

  10. Sweden never closed their secondary schools to kids 16 and below. Things worked fine.

    Of course, Sweden has more cohesive and responsible society.

Leave a Reply