Submitted by Abby Hafer, PhD
At the Board of Health meetings on Dec. 12, 2020, and Jan. 4, 2021, the idea of reducing distancing among children in classrooms was discussed. I would like to address that question.
First, the assertion was made that “There are no published studies on the value of three-foot distancing, rather than six-foot distancing, for children.”
What has been published is that children are perfectly efficient carriers of SARS-CoV-2, the virus responsible for COVID-19. They do sometimes get sick from it, but they are more than capable of transmitting it to others, including their families and friends.
I will now address the two problems with reducing distances from six feet to three. They are: that virus-laden aerosols travel even farther than six feet, and that increasing the occupancy in a room increases danger.
Aerosols travel farther than six feet
A review article in the Journal of Infectious Diseases in fact showed that the virus can travel by aerosol transmission much farther than six feet.
A study published by the Emerging Infectious Diseases journal made it clear that the virus was present in the air around infected people up to four meters (13 feet) away. (https://wwwnc.cdc.gov/eid/article/26/7/20-0885_article).
In the sadly infamous superspreading event involving the choir in Skagit County, Washington, 61 people attended a choir practice with one person who turned out to have COVID-19. As a result, 53 people got sick, three were hospitalized, and two died. (https://www.cdc.gov/mmwr/volumes/69/wr/mm6919e6.htm) It is understood now that the most likely cause of spreading was aerosol transmission, and most of those choir members were seated farther than six feet from that index case. The choir practice took 2½ hours, which is considerably shorter than a school day.
More recently, an airline flight between Dubai and New Zealand that contained one presymptomatic passenger resulted in six others becoming ill. Aerosols are the most likely cause of transmission, even though both the index case and four of the other passengers who got sick reported wearing both masks and gloves during the flight. (https://wwwnc.cdc.gov/eid/article/27/3/20-4714_article).
An airline transmission case from summer 2020 in Ireland showed that 13 people wound up infected after one flight in a plane that was only 17% full. The passengers were spread out throughout the cabin. Masks were worn by nine of those who were sickened during that flight. That flight alone resulted in an outbreak in the greater community, sickening a total of 59 people. Those sickened during the flight included a one-year-old, and the median age of those sickened during the flight was 23. (https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2020.25.42.2001624)
An article in the British Medical Journal points out that the origin of the six-foot rule was based on dispersion of visible droplets, not aerosols; and that aerosolized virus-laden particles can in fact travel much farther than six feet. (https://www.bmj.com/content/370/bmj.m3223)
These studies are just a few of many finding the same thing, that aerosols travel far indoors. Aerosols also do not distinguish between children and adults. They travel the same distances, according to the same physics, whether the people in the room are adults or children. Thus it can be seen that six feet is more of a barely-adequate guideline for indoor areas, rather than something that should be reduced further.
Increasing occupancy increases danger
Reducing distances creates the problem of increasing occupancy. Here the data are also beyond dispute: Increasing the number of people in the same enclosed space increases the risk of viral transmission throughout the space. The British Medical Journal article cited above makes this clear.
Since the entire point behind decreasing distances is to fit more children into the same room, decreasing distances should not be done. Specifically because it will lead to higher occupancy, and higher occupancy will result in more aerosols accumulating in the classroom air. It has been my experience that children in classrooms tend to talk, as do teachers. Speaking raises the level of aerosolized particles that are produced, and shouting produces still more.
The British Medical Journal article points out the following in a diagram: that even masked people, in contact for a prolonged time, in a high-occupancy room who are speaking, have a medium to high risk of transmission of the virus. “In contact for a prolonged time”, by the way, means more than 15 minutes. A school day is much longer than that.
The risk is considered to be medium if the room is well-ventilated, and high if the room is poorly ventilated. I would not count on our schools to have ventilation systems up to the job of keeping rates of viral transmission down. It’s not what they were built for. In fact, it was pointed out in one of the Board of Health meetings that many of our schools’ ventilation systems are energy-saving systems that do not exchange air very often—the opposite of what we need in a pandemic. While the ventilation systems might be tweaked, it seems unlikely that all of ventilation systems in Bedford’s school buildings could be replaced, while school is in session, in time to do much good during this pandemic.
Teachers will also be endangered by increasing the occupancy in the classroom. Even while considering the reduction of distances to three feet for children, members of the board have reiterated the need to protect adult teachers and staff by keeping the six-foot distancing rule for the teachers. But if you put a teacher into a high-occupancy classroom, is still a high occupancy classroom, which that teacher will inhabit for several hours as the aerosols accumulate. Keeping a six-foot distancing rule for teachers may seem like a nice gesture, but it does not offer the more realistic safety that six feet of distancing for everyone does, with its necessary effect of reducing occupancy in classrooms.
The distancing guidelines that we now have in effect are working—our rates of in-school transmission are low. That shows that the six-foot guideline works—not that it should be discarded.
Please note the second table from the top, labeled “Wearing face coverings, contact for a prolonged time”. If you look at the portion of the table on the right, labeled “High Occupancy”, you will see that the risk level is never less than medium even with masks, in an indoor space with people speaking—and the risk is raised to high when the room is poorly ventilated, as is probably the case with our schools.