The Centers for Disease Control and Prevention is clear and consistent in its recommendation on social distance: to reduce the risk of contracting the coronavirus, people should stay at least six meters away from others who are not in their households. The guideline applies whether you are eating in a restaurant, lifting weights at a gym or learning a long class in a fourth grade class.
The guideline was particularly important for schools, many of which have not been reopened because they do not have enough space to keep students six meters apart.
Now urged by a better understanding of how the virus spreads and a growing concern about the harm children should keep out of school, calls on the agency to reduce the recommended distance in schools from six feet to three.
“It never occurred to me that six feet were particularly sensational in the context of mitigation,” said Dr. Ashish Jha, dean of the Brown University School of Public Health, said. “I wish the CDC would just come forward and say this is not a big issue.”
Dr. Anthony S. Fauci, the director of the National Institute of Allergy and Infectious Diseases, said Sunday, told CNN that the CDC was to review the case.
The idea remains controversial, in part because few studies have directly compared different distance strategies. But the case also boils down to a devilishly difficult and often personal question: How safe is safe enough?
“There is no magic threshold for any distance,” says Dr. Benjamin Linas, a specialist in infectious diseases at Boston University. ‘There’s a six foot risk, there’s a three foot risk, and there’s a nine foot risk. There is always a risk. “He added, ‘The question is just how much of a risk? And what do you give up in return? ”
The origin of six feet
The origin of the six-foot distance recommendation is something of a mystery. “It’s almost like it’s been ripped out of thin air,” said Linsey Marr, a viral transmission expert at Virginia Tech University.
When the virus first appeared, many experts believed that it was mainly transmitted by large respiratory droplets, which are relatively heavy. Ancient scientific studies, some of which date back more than a century, have suggested that these droplets tend to move no more than three to six feet. This observation, as well as an abundance of caution, may have prompted the CDC to make its six-foot proposal, Drs. Marr said.
But the recommendation was not universal. The American Academy of Pediatrics recommends social distance of three to six feet in schools, but the World Health Organization recommends only one meter or 3.3 feet.
And over the past year, scientists have learned that respiratory drops are not the primary mode of transmission of coronavirus. Instead, the virus mostly spreads through small droplets in the air, known as aerosols, which can travel longer distances and flow through rooms in unpredictable ways.
Data also suggest that schools are relatively low-risk environments; Children under 10 seem to transmit the virus less easily than adults.
In recent months, there have been hints that the distance of six meters is not necessary in the school environment. Business rates were generally low, even in schools with a weakened policy. “We know that many schools have opened up to less than six meters and have not yet seen major outbreaks,” Dr Jha said.
In a 2020 analysis of observational studies in different environments, researchers found that the physical distance of at least one meter significantly reduced the transmission rates of various coronaviruses, including the one causing Covid-19. But they found evidence to suggest that a two-meter guideline could be ‘more effective’.
“One of the key data missing is a direct head-to-head comparison of sites that have implemented three-foot-to-six-foot-distance,” said Dr. Elissa Perkins, director of infectious emergency medicine. management at Boston University of Medicine.
Dr. Perkins and her colleagues recently made such a comparison using a natural experiment in Massachusetts. Last summer, the state Department of Education issued guidelines to recommend distances of three to six feet in schools that would reopen in the fall. As a result, school policies varied: some districts imposed strict distances of six feet, while others required only three. (The state required all staff members, as well as students in the second grade and above, to wear masks.)
The researchers found that the social distance strategy had no statistically significant effect on the Covid-19 rate the team reported in the journal Clinical Infectious Diseases last week. The study also found that Covid-19 prices were lower in schools than in the surrounding communities.
The authors say that the findings provide the assurance that schools can relax their distance requirements and still be safe, provided they take other precautions, such as wearing universal masks.
“Masking still seems to be effective,” said dr. Westyn Branch-Elliman, an infectious disease specialist at the VA Boston Healthcare System, said. “And if I have universal masking mandates, I think it’s reasonable to go for a three-foot recommendation.”
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Not everyone finds the study so convincing. A. Marm Kilpatrick, a researcher of infectious diseases at the University of California, Santa Cruz, said the school district’s data is too noisy to draw firm conclusions from it. “It doesn’t really allow you to get an answer you can really trust,” he said.
The authors of the study acknowledged that they cannot rule out the possibility that increased distance may provide a small benefit.
With aerosol transfer, safety usually increases with distance; the further the aerosols move, the more it is diluted. “It’s like being near a smoker,” said Dr. Marr said. “The closer you are, the more you will inhale.”
And at a distance, the more people there are in a room, the greater the chance that one of them will be infected with the coronavirus. A six-foot rule helps reduce the risk, said Donald Milton, an aerosol expert at the University of Maryland: “If people are six feet apart, you can not pack it. It is therefore safer because it is less dense. ”
Masks and good ventilation help a lot to reduce the risk. With these measures in place, the difference between three and six feet was likely to be relatively small, scientists said. And if Covid-19 is not very common in the surrounding community, the absolute risk of contracting the virus in schools is likely to remain low as long as this protection exists.
“We can always do things to further reduce our risks,” said Dr. Marr said. “But at some point, you’re declining returns and you have to think about the cost of trying to achieve the additional risk reduction.”
Debate and diminishing risks
Some experts believe that the benefits of reopening schools outweigh a small increase in risks. “If we try to follow the six-foot guidelines, it should not prevent us from getting children back to school full-time with masks, at least three feet away,” said Dr. Marr said.
Others said it was too soon to loosen the CDC guidelines. “Ultimately, I think there could be a place for this changing leadership,” Saskia Popescu, an epidemiologist at Infectious Diseases at George Mason University, said in an email. “But it is not now, if we are struggling to vaccinate people, we are still seeing more than 60,000 cases a day and we are not trying to stop the progress we have made.”
Even proponents of changing the guideline say that there should be careful and in combination with other precautions to move towards weakening. “If you’re in an area where there’s no strong tendency to rely on masks, I think it would not be wise to extrapolate our data to that environment,” said Dr. Perkins said.
In addition, officials run the risk of muddying the messages about public health if they set different standards for schools than for other shared spaces. “I developed about this,” said Dr. Linas said. “Last summer I felt like, ‘How are we going to explain to people that it’s six meters everywhere except for schools? It does not seem consistent and problematic. ‘”
But schools are unique, he said. These are relatively controlled environments that can apply certain safety measures, and they have unique benefits for society. “The benefits of school differ from the benefits of cinemas or restaurants,” he said. “So I’m willing to take a little more risk just to keep it open.”