Posts filed under ‘Policy’

The Science of COVID-19 Prevention for Teachers.

An evolving list of questions and some answers.  Updated 6.26.2020

I’m about to go back into the classroom, a science lab in a beautiful middle school in the San Francisco Bay Area. A school in such a lovely setting I thought I’d fallen into paradise when I interviewed there almost thirty years ago. 

Distance learning using Zoom and Google Classroom, has not been a disaster in my district. We are lucky to have 100% access to hot spots and devices. Learning did continue albeit at a slower rate with less playfulness and fun, less opportunity for informal interaction. I miss the joy of in person teaching and my heart hurts for some of my students who were clearly suffering from loneliness and depression, only barely making out of bed to a Zoom if they were there at all. 

But the epidemic is on the uptick again after optimism in May that we might be able to open school safely in August. 

Four infectious public health experts rank activities for risk in this article in MLive on June 8th, “The doctors pointed to five factors, when considering how risky a given activity might be: 

  • Whether it’s inside or outside; 
  • proximity to others; 
  • exposure time; 
  • likelihood of compliance; and 
  • personal risk level. 

They rank schools as more risky than casinos and indoor dining at restaurants, even with social distancing and hygiene because students will likely be within 6 feet of each other for long periods of time “…with the added challenge of getting children to follow precautions like staying separated, wearing a mask and washing hands well.” – My colleagues and I cannot be the pandemic police at all times or we will get no learning done and relationships will be seriously strained. 

Even so, based on a survey at the end of May, about 75% of our parents want school to return full time and are very vocal about it at school board meetings – child care is uppermost as parents struggle to return to work. Children are suffering, losing ground academically and socially. We are under enormous pressure to return to on-site, in person education on August 11th. The need to figure out the effectiveness of the virus prevention strategies in school settings is urgent. 

To put the need to protect teachers in context: In the 2017–18 school year, there were 3.3 million full-time and part-time traditional public school teachers, 205,600 public charter school teachers, and 509,200 private school teachers. The teaching profession has many members who are in high risk categories. 18.8% of teachers in the US are over 55 according to the National Center for Education Statistics. As of 4.3.202, here are some of the teachers who have died so far on EdWeek. So far 30 teachers have died in New York. 

This epidemic will be a relatively small blip in children’s education: Anthony Fauci suggests that a vaccine may be available by January 2021, there are new treatments emerging and testing and tracing is ramping up. Balance that against the real risk of preventable deaths in our communities – grandparent infected by hugging his twin grandsons on a rare visit where they thought they were being careful, a parent recovering from cancer, a teacher who is quietly HIV+.

It’s bad enough if a teacher fails to come to class the day after the Oakland Hills Fire. Dr.Loggins had gone back for his cat and disappeared forever. The cohort of 6th graders who loved him, never really did recover from the trauma. Imagine the grief and fear when a teacher dies from an infection that their students and families may have also caught. 

Elementary teachers will be expected to be in rooms with 28 students on average, or 28 students over the course of a week if a hybrid model is adopted. Secondary teachers will be exposed to many more students – their average teaching load is in the range of 90 to 160 students a day or a week, depending on the school schedule. Teachers are some of the most exposed professions as evidenced by the common experience of infectious illness in your first year of teaching in a new school due to the close proximity over a long time indoors to a large number of contacts. 

We are in the middle of an economic collapse and school budgets will be seriously impacted. We need research-based, inexpensive and practical infection prevention. 

Here’s an evolving list of urgent, life and death experimental questions teachers have

  1. Do children get and spread Coronavirus? Studies currently indicate that student to student spread of the Coronavirus is less of an issue than the spread from adult to adult. Child to adult spread, and teen to adult spread has not yet been shown to be significant but this may be because there has not been enough time, nor enough schools opening in fairly normal ways for this to be conclusive. I can see no real reason why a young person with a viral load (asymptomatic or pre-symptomatic) would not be able to spread the virus to their teachers. See Nature “How do Children Spread the Coronavirus? The Science Still Isn’t Clear.”

2. What is the best way of diluting viral droplets and aerosols?

a. Being outside: The most widely touted ways to keep safe is to dilute viral load by being outside and distanced. But weather, connectivity and space restrictions do not always allow that. 


b. What is the most effective way of reducing infection risk with ventilation? – with box fans? With HVAC systems that suck or blow? Where, how? What filters work best? What are the costs?

How Healthy Buildings Can Fight Coronavirus” Financial Times March 2020 suggests that air flow needs to go from clean (outside air) to dirty (classroom air 🙂 So having HVAC systems sucking air out of the room is better than blowing air into the room. Box fans blowing air into the room is better than blowing air out of the room. Probably. There are filtration systems available that will recirculate cleaner air if outside ventilation is not easily possible. 




It’s important to check ventilation is not accidentally blowing dirty air into another classroom. SARS was spread like this in a Hong Kong hotel in 2003. Here is original research and analysis from JThoracic Disease 2018. 


3. How effective are plexiglass shields? Which designs are better at preventing infection? These are expensive and interfere with student/teacher communication. Is it worth it? Research needed here.

4. How effective and necessary is frequent swabbing of desks and door knobs? It’s a lot of work for how much gain? The main spread is via droplets and aerosol. Surface contact is a secondary means. Needs more research.

5. Is hand sanitizer for students and teachers good enough for infection prevention or is the additional nuisance of handwashing worth it?

6. Does the enormous chaos of staggered and/or hybrid schedules to limit number of students in a class make a big enough difference to be worth it? Is “6 feet” a magic distance? 3ft would allow classes to resume as normal – we can fit that distancing into most classrooms. 

The effectiveness of social distancing has been evaluated in a meta-analysis in the Lancet, June 1st – 1 meter or more is increasingly effective. There is no ‘boundary’ distance. Risk falls off with the inverse square law: 1/distance squared.

7. Do we have to have all children facing the front? It will take us back to the ‘sage on the stage’ model of instruction. How bad is having kids at tables to do group work? Research needed.


Mask Questions:IMG_0551 

  1. Which kinds of face mask currently and widely available are the most effective at preventing infection? (Air flow, droplet and aerosol flow, field studies) 


The Mayo Clinic “How Much Protection do Facemasks Offer?” 5.28.2020 and British Medical Journal study showing that medical masks offer better protection than cloth.

“We conclude that wearing of face masks in public corresponds to the most effective means to prevent interhuman transmission, and this inexpensive practice, in conjunction with extensive testing, quarantine, and contact tracking, poses the most probable fighting opportunity to stop the COVID-19 pandemic, prior to the development of a vaccine.” in Identifying Airborne Transmission as the Dominant Way of Spread for COVID-19” PNAS 6.2020 

Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks from ACS finds that double-layered cloth masks that fit well, especially if tightly woven greatly reduce droplet and aerosol transmission. 

Nature Briefs Respiritory Virus Shedding and Masks reports similar findings. 

Research started at Texas Tech University May 20th and in Nature Medicine April 2nd, show convincing evidence that surgical masks do significantly reduce droplet and aerosol transmission from symptomatic individuals. It is not clear how effective masks are for say, a teacher in a class with asymptomatic or pre-symptomatic children who are not or cannot wear a mask. 

The mask must be properly sealed against the face with a nose wire, around the cheeks and under the chin. This is NOT true for many home made and loose-fitting masks. 

Surgical masks are now available through Amazon for about $20 for 50 surgical masks. 

Materials and layering make a difference – some cloth homemade masks are unlikely to be effective. Double layers of tightly woven cotton, or layers of two different materials work better at filtration. 

Another meta analysis in the Lancet 6.1.202 statesFace mask use could result in a large reduction in risk of infection” especially N95 respirators (probably not practical in a classroom setting).   

The masks with valves on them protect the wearer but allow unfiltered exhaled breath out. Schools should consider not allowing these kinds of masks and have replacement medical masks to offer students turning up in them. 

However, Coronavirus spread and is still spreading like wildfire in nursing homes even after most there were wearing masks. Prisons too – although mask wearing may be lower there. Meat packing plants have people in closer proximity but in much larger facilities than classrooms and they were wearing masks from early in the epidemic. Masks do offer significant protection if worn consistently by everyone. But how will teachers enforce this on very hot days? With very young children? In classes where classroom management is not the best? 

2. Can you take the mask off in between periods? 

Intermittent masking even with respirators was NOT effective at reducing transmission according to the Lancet article. Gah! You could probably go outside and take your mask off though. Not in the classroom with the hot fugh of child breath though 🙂

3. How effective are face shields? Can they be modified perhaps with a cloth gasket around the bottom and side to provide improved infection prevention without obscuring the teacher’s face? 

Eye covering has been indicated in some of the meta analyses mentioned above. However, face shields do seal around the face so there is more potential for droplets to get in and out compared to a mask. Face shields supplement a mask but do not replace it. 

How necessary are new masks/laundering masks or can they be worn several times?

4. Research your own preferences:

a. Which kinds of mask allow you to breathe easily and do not get too wet and uncomfortable over the course of a day?

b. Which kinds of mask will allow you to talk to a class without muffling and distorting sound too much? 

c. Which kinds of mask will not be too intimidating to children?

Uncomfortable masks will not be worn consistently. The N95 masks that cup your face are too tight and restrict the jaw making it hard to talk. 

Minimal coverage, allowing eyes and more of the face to be seen. There is a cool design of face shields with a loose-fitting cloth gasket around it here. That might be much better as students can see your whole face. Some masks have a clear panel in them which I think looks kind of freaky. But then, maybe my uncovered face looks kind of freaky so there is that. 


June 26, 2020 at 8:12 AM 1 comment

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