Masks and Distancing Won't Be Enough to Prevent School Outbreaks, Latest Science Suggests
Never has the prospect of "back to school" seemed so ominous as it does in 2020. As the number of COVID-19 cases climb steadily in nearly every state, the prospect of in-person classes are filling students, parents, and faculty alike with a corresponding sense of dread.
The notion that children are immune or resistant to SARS-CoV-2 is demonstrably untrue.
The decision to resume classes at primary, secondary, and collegiate levels is not one that should be regarded lightly, particularly as coronavirus cases skyrocket across the United States.
What should be a measured, data-driven discussion that weighs risks and benefits has been derailed by political talking points. President Trump has been steadily advocating for an unfettered return to the classroom, often through imperative "OPEN THE SCHOOLS!!!" tweets. In July, Secretary of Education Betsy DeVos threatened to withhold funding from schools that did not reopen for full-time, in-person classes, despite not having the authority to do so. Like so many public health issues, opening schools in the midst of a generational pandemic has been politicized to the point that the question of whether it is safe to do so has been obscured and confounded. However, this question still deserves to be examined based on evidence.
What We Know About Kids and COVID-19
Some arguments for returning to in-person education have focused on the fact that children and young adults are less susceptible to severe disease. In some cases, people have stated that children cannot be infected, pointing to countries that have resumed in-person education with no associated outbreaks. However, those countries had extremely low community transmission and robust testing and surveillance.
The notion that children are immune or resistant to SARS-CoV-2 is demonstrably untrue: children can be infected, they can become sick, and, in rare cases, they can die. Children can also transmit the virus to others, especially if they are in prolonged proximity to them. A Georgia sleepaway camp was the site of at least 260 cases among mostly children and teenagers, some as young as 6 years old. Children have been shown to shed infectious virus in their nasal secretions and have viral loads comparable to adults. Children can unquestionably be infected with SARS-CoV-2 and spread it to others.
The more data emerges, the more it appears that both primary and secondary schools and universities alike are conducive environments for super-spreading. Mitigating these risks depends heavily on individual schools' ability to enforce reduction measures. So far, the evidence demonstrates that in most cases, schools are unable to adequately protect students or staff. A school superintendent from a small district in Arizona recently described an outbreak that occurred among staff prior to in-person classes resuming. Schools that have opened so far have almost immediately reported new clusters of cases among students or staff.
This is because it is impossible to completely eliminate risk even with the most thoughtful mitigation measures when community transmission is high. Risk can be reduced, but the greater the likelihood that someone will be exposed in the community, the greater the risk they might pass the virus to others on campus or in the classroom.
There are still many unknowns about SARS-CoV-2 transmission, but some environments are known risks for virus transmission: enclosed spaces with crowds of people in close proximity over extended durations. Transmission is thought to occur predominantly through inhaled aerosols or droplets containing SARS-CoV-2, which are produced through common school activities such as breathing, speaking, or singing. Masks reduce but do not eliminate the production of these aerosols. Implementing universal mask-wearing and physical distancing guidelines will furthermore be extraordinarily challenging for very young children.
Smaller particle aerosols can remain suspended in the air and accumulate over time. In an enclosed space where people are gathering, such as a classroom, this renders risk mitigation measures such as physical distancing and masks ineffective. Many classrooms at all levels of education are not conducive to improving ventilation through low-cost measures such as opening windows, much less installing costly air filtration systems.
As a risk reduction measure, ventilation greatly depends on factors like window placement, window type, room size, room occupancy, building HVAC systems, and overall airflow. There isn't much hard data on the specific effects of ventilation on virus transmission, and the models that support ventilation rely on assumptions based on scant experimental evidence that doesn't account for virologic parameters.
There is also no data about how effective air filtration or UV systems would be for SARS-CoV-2 transmission risk reduction, so it's hard to say if this would result in a meaningful risk reduction or not. We don't have enough data outside of a hospital setting to support that ventilation and/or filtration would significantly reduce risk, and it's impractical (and most likely impossible in most schools) to implement hospital ventilation systems, which would likely require massive remodeling of existing HVAC infrastructure. In a close contact situation, the risk reduction might be minimal anyway since it's difficult to avoid exposure to respiratory aerosols and droplets a person is exhaling.
You'd need to get very low rates in the local community to open safely in person regardless of other risk reduction measures, and this would need to be complemented by robust testing and contact tracing capacity.
Efforts to resume in-person education depend heavily on school health and safety plans, which often rely on self-reporting of symptoms due to insufficient testing capacity. Self-reporting is notoriously unreliable, and furthermore, SARS-CoV-2 can be readily transmitted by pre-symptomatic individuals who may be unaware that they are sick, making testing an essential component of any such plan. Primary and secondary schools are faced with limited access to testing and no funds to support it. Even in institutions that include a testing component in their reopening plans, this is still too infrequent to support the full student body returning to campus.
Economic Conflicts of Interest
Rebecca Harrison, a PhD candidate at Cornell University serving on the campus reopening committee, is concerned that her institution's plan places too much faith in testing capacity and is over-reliant on untested models. Harrison says that, as a result, students are being implicitly encouraged to return to campus and "very little has been done to actively encourage students who are safe and able to stay home, to actually stay home."
Harrison also is concerned that her institution "presumably hopes to draw students back from the safety of their parents' basements to (re)join the residential campus experience ... and drive revenue." This is a legitimate concern. Some schools may be actively thwarting safety plans in place to protect students based on financial incentives. Student athletes at Colorado State have alleged that football coaches told them not to report COVID-19 symptoms and are manipulating contact tracing reports.
Public primary and secondary schools are not dependent on student athletics for revenue, but nonetheless are susceptible to state and federal policies that tie reopening to budgets. If schools are forced to make decisions based on a balance sheet, rather than the health and safety of students, teachers, and staff, they will implement health and safety plans that are inadequate. Schools will become ground zero for new clusters of cases.
Looking Ahead: When Will Schools Be Able to Open Again?
One crucial measure is the percent positivity rate in the local community, the number of positive tests based on all the tests that are done. Some states, like California, have implemented policies guiding the reopening of schools that depend in part on a local community's percent positivity rate falling under 8 percent, among other benchmarks including the rate of new daily cases. Currently, statewide, test positivity is below 7%, with an average of 3 new daily cases per 1000 people per day. However, the California department of health acknowledges that new cases per day are underreported. There are 6.3 million students in the California public school system, suggesting that at any given time, there could be nearly 20,000 students who might be contagious, without accounting for presymptomatic teachers and staff. In the classroom environment, just one of those positive cases could spread the virus to many people in one day despite masks, distancing, and ventilation.
You'd need to get very low rates in the local community to open safely in person regardless of other risk reduction measures, and this would need to be complemented by robust testing and contact tracing capacity. Only with rapid identification and isolation of new cases, followed by contact tracing and quarantine, can we break chains of transmission and prevent further spread in the school and the larger community.
None of these safety concerns diminish the many harms associated with the sudden and haphazard way remote learning has been implemented. Online education has not been effective in many cases and is difficult to implement equitably. Young children, in particular, are deprived of the essential social and intellectual development they would normally get in a classroom with teachers and their peers. Parents of young children are equally unprepared and unable to provide full-time instruction. Our federal leadership's catastrophic failure to contain the pandemic like other countries has put us in this terrible position, where we must choose between learning or spreading a deadly pathogen.
Blame aside, parents, educators, and administrators must decide whether to resume in-person classes this fall. Those decisions should be based on evidence, not on politics or economics. The data clearly shows that community transmission is out of control throughout most of the country. Thus, we ignore the risk of school outbreaks at our peril.
[Editor's Note: Here's the other essay in the Back to School series: 5 Key Questions to Consider Before Sending Your Child Back to School.]
Two-and-a-half year-old Huckleberry, a blue merle Australian shepherd, pulls hard at her leash; her yelps can be heard by skiers and boarders high above on the chairlift that carries them over the ski patrol hut to the top of the mountain. Huckleberry is an avalanche rescue dog — or avy dog, for short. She lives and works with her owner and handler, a ski patroller at Breckenridge Ski Resort in Colorado. As she watches the trainer play a game of hide-and-seek with six-month-old Lume, a golden retriever and avy dog-in-training, Huckleberry continues to strain on her leash; she loves the game. Hide-and-seek is one of the key training methods for teaching avy dogs the rescue skills they need to find someone caught in an avalanche — skier, snowmobiler, hiker, climber.
Lume’s owner waves a T-shirt in front of the puppy. While another patroller holds him back, Lume’s owner runs away and hides. About a minute later — after a lot of barking — Lume is released and commanded to “search.” He springs free, running around the hut to find his owner who reacts with a great amount of excitement and fanfare. Lume’s scent training will continue for the rest of the ski season (Breckenridge plans operating through May or as long as weather permits) and through the off-season. “We make this game progressively harder by not allowing the dog watch the victim run away,” explains Dave Leffler, Breckenridge's ski patroller and head of the avy dog program, who has owned, trained and raised many of them. Eventually, the trainers “dig an open hole in the snow to duck out of sight and gradually turn the hole into a cave where the dog has to dig to get the victim,” explains Leffler.
By the time he is three, Lume, like Huckleberry, will be a fully trained avy pup and will join seven other avy dogs on Breckenridge ski patrol team. Some of the team members, both human and canine, are also certified to work with Colorado Rapid Avalanche Deployment, a coordinated response team that works with the Summit County Sheriff’s office for avalanche emergencies outside of the ski slopes’ boundaries.
There have been 19 avalanche deaths in the U.S. this season, according to avalanche.org, which tracks slides; eight in Colorado. During the entirety of last season there were 17. Avalanche season runs from November through June, but avalanches can occur year-round.
High tech and high stakes
Complementing avy dogs’ ability to smell people buried in a slide, avalanche detection, rescue and recovery is becoming increasingly high tech. There are transceivers, signal locators, ground scanners and drones, which are considered “games changers” by many in avalanche rescue and recovery
For a person buried in an avalanche, the chance of survival plummets after 20 minutes, so every moment counts.
A drone can provide thermal imaging of objects caught in a slide; what looks like a rock from far away might be a human with a heat signature. Transceivers, also known as beacons, send a signal from an avalanche victim to a companion. Signal locators, like RECCO reflectors which are often sewn directly into gear, can echo back a radar signal sent by a detector; most ski resorts have RECCO detector units.
Research suggests that Ground Penetrating Radar (GPR), an electromagnetic tool used by geophysicists to pull images from inside the ground, could be used to locate an avalanche victim. A new study from the Department of Energy’s Sandia National Laboratories suggests that a computer program developed to pinpoint the source of a chemical or biological terrorist attack could also be used to find someone submerged in an avalanche. The search algorithm allows for small robots (described as cockroach-sized) to “swarm” a search area. Researchers say that this distributed optimization algorithm can help find avalanche victims four times faster than current search mechanisms. For a person buried in an avalanche, the chance of survival plummets after 20 minutes, so every moment counts.
An avy dog in training is picking up scent
Sarah McLear
While rescue gear has been evolving, predicting when a slab will fall remains an emerging science — kind of where weather forecasting science was in the 1980s. Avalanche forecasting still relies on documenting avalanches by going out and looking,” says Ethan Greene, director of the Colorado Avalanche Information Center (CAIC). “So if there's a big snowstorm, and as you might remember, most avalanches happened during snowstorms, we could have 10,000 avalanches that release and we document 50,” says Greene. “Avalanche forecasting is essentially pattern recognition,” he adds--and understanding the layering structure of snow.
However, determining where the hazards lie can be tricky. While a dense layer of snow over a softer, weaker layer may be a recipe for an avalanche, there’s so much variability in snowpack that no one formula can predict the trigger. Further, observing and measuring snow at a single point may not be representative of all nearby slopes. Finally, there’s not enough historical data to help avalanche scientists create better prediction models.
That, however, may be changing.
Last year, an international group of researchers created computer simulations of snow cover using 16 years of meteorological data to forecast avalanche hazards, publishing their research in Cold Regions Science and Technology. They believe their models, which categorize different kinds of avalanches, can support forecasting and determine whether the avalanche is natural (caused by temperature changes, wind, additional snowfall) or artificial (triggered by a human or animal).
With smell receptors ranging from 800 million for an average dog, to 4 billion for scent hounds, canines remain key to finding people caught in slides.
With data from two sites in British Columbia and one in Switzerland, researchers built computer simulations of five different avalanche types. “In terms of real time avalanche forecasting, this has potential to fill in a lot of data gaps, where we don't have field observations of what the snow looks like,” says Simon Horton, a postdoctoral fellow with the Simon Fraser University Centre for Natural Hazards Research and a forecaster with Avalanche Canada, who participated in the study. While complex models that simulate snowpack layers have been around for a few decades, they weren’t easy to apply until recently. “It's been difficult to find out how to apply that to actual decision-making and improving safety,” says Horton. If you can derive avalanche problem types from simulated snowpack properties, he says, you’ll learn “a lot about how you want to manage that risk.”
The five categories include “new snow,” which is unstable and slides down the slope, “wet snow,” when rain or heat makes it liquidly, as well as “wind-drifted snow,” “persistent weak layers” and “old snow.” “That's when there's some type of deeply buried weak layer in the snow that releases without any real change in the weather,” Horton explains. “These ones tend to cause the most accidents.” One step by a person on that structurally weak layer of snow will cause a slide. Horton is hopeful that computer simulations of avalanche types can be used by scientists in different snow climates to help predict hazard levels.
Greene is doubtful. “If you have six slopes that are lined up next to each other, and you're going to try to predict which one avalanches and the exact dimensions and what time, that's going to be really hard to do. And I think it's going to be a long time before we're able to do that,” says Greene.
What both researchers do agree on, though, is that what avalanche prediction really needs is better imagery through satellite detection. “Just being able to count the number of avalanches that are out there will have a huge impact on what we do,” Greene says. “[Satellites] will change what we do, dramatically.” In a 2022 paper, scientists at the University of Aberdeen in England used satellites to study two deadly Himalayan avalanches. The imaging helped them determine that sediment from a 2016 ice avalanche plus subsequent snow avalanches contributed to the 2021 avalanche that caused a flash flood, killing over 200 people. The researchers say that understanding the avalanches characteristics through satellite imagery can inform them how one such event increases the magnitude of another in the same area.
Avy dogs trainers hide in dug-out holes in the snow, teaching the dogs to find buried victims
Sarah McLear
Lifesaving combo: human tech and Mother Nature’s gear
Even as avalanche forecasting evolves, dogs with their built-in rescue mechanisms will remain invaluable. With smell receptors ranging from 800 million for an average dog, to 4 billion for scent hounds, canines remain key to finding people caught in slides. (Humans in comparison, have a meager 12 million.) A new study published in the Journal of Neuroscience revealed that in dogs smell and vision are connected in the brain, which has not been found in other animals. “They can detect the smell of their owner's fingerprints on a glass slide six weeks after they touched it,” says Nicholas Dodman, professor emeritus at Cummings School of Veterinary Medicine at Tufts University. “And they can track from a boat where a box filled with meat was buried in the water, 100 feet below,” says Dodman, who is also co-founder and president of the Center for Canine Behavior Studies.
Another recent study from Queens College in Belfast, United Kingdom, further confirms that dogs can smell when humans are stressed. They can also detect the smell of a person’s breath and the smell of the skin cells of a deceased person.
The emerging avalanche-predicting human-made tech and the incredible nature-made tech of dogs’ olfactory talents is the lifesaving “equipment” that Leffler believes in. Even when human-made technology develops further, it will be most efficient when used together with the millions of dogs’ smell receptors, Leffler believes. “It is a combination of technology and the avalanche dog that will always be effective in finding an avalanche victim.”
Living with someone changes your microbiome, new research shows
Some roommate frustration can be expected, whether it’s a sink piled high with crusty dishes or crumbs where a clean tabletop should be. Now, research suggests a less familiar issue: person-to-person transmission of shared bacterial strains in our gut and oral microbiomes. For the first time, the lab of Nicola Segata, a professor of genetics and computational biology at the University of Trento, located in Italy, has shown that bacteria of the microbiome are transmitted between many individuals, not just infants and their mothers, in ways that can’t be explained by their shared diet or geography.
It’s a finding with wide-ranging implications, yet frustratingly few predictable outcomes. Our microbiomes are an ever-growing and changing collection of helpful and harmful bacteria that we begin to accumulate the moment we’re born, but experts are still struggling to unravel why and how bacteria from one person’s gut or mouth become established in another person’s microbiome, as opposed to simply passing through.
“If we are looking at the overall species composition of the microbiome, then there is an effect of age of course, and many other factors,” Segata says. “But if we are looking at where our strains are coming from, 99 percent of them are only present in other people’s guts. They need to come from other guts.”
If we could better understand this process, we might be able to control and use it; perhaps hospital patients could avoid infections from other patients when their microbiome is depleted by antibiotics and their immune system is weakened, for example. But scientists are just beginning to link human microbiomes with various ailments. Growing evidence shows that our microbiomes steer our long-term health, impacting conditions like obesity, irritable bowel syndrome, type 2 diabetes, and cancer.
Previous work from Segata’s lab and others illuminated the ways bacteria are passed from mothers to infants during the first few months of life during vaginal birth, breastfeeding and other close contact. And scientists have long known that people in close proximity tend to share bacteria. But the factors related to that overlap, such as genetics and diet, were unclear, especially outside the mother-baby dyad.
“If we look at strain sharing between a mother and an infant at five years of age, for example, we cannot really tell which was due to transmission at birth and which is due to continued transmission because of contact,” Segata says. Experts hypothesized that they could be caused by bacterial similarities in the environment itself, genetics, or bacteria from shared foods that colonized the guts of people in close contact.
Strain sharing was highest in mother-child pairs, with 96 percent of them sharing strains, and only slightly lower in members of shared households, at 95 percent.
In Italy, researchers led by Mireia Valles-Colomer, including Segata, hoped to unravel this mystery. They compared data from 9,715 stool and saliva samples in 31 genomic datasets with existing metadata. Scientists zoomed in on variations in each bacterial strain down to the individual level. They examined not only mother-child pairs, but people living in the same household, adult twins, and people living in the same village in a level of detail that wasn’t possible before, due to its high cost and difficulties in retrieving data about interactions between individuals, Segata explained.
“This paper is, with high granularity, quantifying the percent sharing that you expect between different types of social interactions, controlling for things like genetics and diet,” Gibbons says. Strain sharing was highest in mother-child pairs, with 96 percent of them sharing strains, and only slightly lower in members of shared households, at 95 percent. And at least half of the mother-infant pairs shared 30 percent of their strains; the median was 12 percent among people in shared households. Yet, there was no sharing among eight percent of adult twins who lived separately, and 16 percent of people within villages who resided in different households. The results were published in Nature.
It’s not a regional phenomenon. Although the types of bacterial strains varied depending on whether people lived in western and eastern nations — datasets were drawn from 20 countries on five continents — the patterns of sharing were much the same. To establish these links, scientists focused on individual variations in shared bacterial strains, differences that create unique bacterial “fingerprints” in each person, while controlling for variables like diet, demonstrating that the bacteria had been transmitted between people and were not the result of environmental similarities.
The impact of this bacterial sharing isn’t clear, but shouldn’t be viewed with trepidation, according to Sean Gibbons, a microbiome scientist at the nonprofit Institute for Systems Biology.
“The vast majority of these bugs are actually either benign or beneficial to our health, and the fact that we're swapping and sharing them and that we can take someone else's strain and supplement or better diversify our own little garden is not necessarily a bad thing,” he says.
"There are hundreds of billions of dollars of investment capital moving into these microbiome therapeutic companies; bugs as drugs, so to speak,” says Sean Gibbons, a microbiome scientist at the Institute for Systems Biology.
Everyday habits like exercising and eating vegetables promote a healthy, balanced gut microbiome, which is linked to better metabolic and immune function, and fewer illnesses. While many people’s microbiomes contain bacteria like C. diff or E. coli, these bacteria don’t cause diseases in most cases because they’re present in low levels. But a microbiome that’s been wiped out by, say, antibiotics, may no longer keep these bacteria in check, allowing them to proliferate and make us sick.
“A big challenge in the microbiome field is being able to rationally predict whether, if you're exposed to a particular bug, it will stick in the context of your specific microbiome,” Gibbons says.
Gibbons predicts that explorations of microbe-based therapeutics will be “exploding” in the coming decades. “There are hundreds of billions of dollars of investment capital moving into these microbiome therapeutic companies; bugs as drugs, so to speak,” he says. Rather than taking a mass-marketed probiotic, a precise understanding of an individual’s microbiome could help target the introduction of just the right bacteria at just the right time to prevent or treat a particular illness.
Because the current study did not differentiate between different types of contact or relationships among household members sharing bacterial strains or determine the direction of transmission, Segata says his current project is examining children in daycare settings and tracking their microbiomes over time to understand the role genetics and everyday interactions play in the level of transmission that occurs.
This relatively newfound ability to trace bacterial variants to minute levels has unlocked the chance for scientists to untangle when and how bacteria leap from one microbiome to another. As researchers come to better understand the factors that permit a strain to establish itself within a microbiome, they could uncover new strategies to control these microbes, harnessing the makeup of each microbiome to help people to resist life-altering medical conditions.