The pandemic has launched almost constant cleaning and disinfecting in schools. But as experts learn more about how the virus spreads, some research raises questions about the right amount of cleaning, and how sanitation protocols can support other COVID-19 prevention measures in the school.
Cleaning and disinfecting are core strategies to control the spread of the coronavirus, according to the consensus from the Centers for Disease Control and Prevention, the World Health Organization, and others. And they have been among the most universally adopted among schools reopening this year.
A nationally representative survey of educators conducted in February by the EdWeek Research Center found 91 percent report more-intensive cleaning protocols, and 85 percent say that disinfectant wipes are now widely available in classrooms, an 8 percentage point increase compared to this June.
While cleaning uses soap or detergent to remove surface germs, disinfecting uses chemicals to kill or inactivate bacteria and viruses like COVID-19 after a surface has been cleaned. According to the CDC and other guidance, it’s most effective for schools to do both in order to reduce the spread of COVID, particularly on frequently used surfaces like door handles, light switches, and shared electronics such as keyboards, mice, or printers.
Other countries have varied significantly in both how often they clean and disinfect schools and how closely they involve teachers and students in doing so. While schools across WHO countries encourage wiping down frequently used surfaces every two hours, Denmark requires that any early-childhood materials be cleaned twice a day and any keyboards cleaned after each use.
Studies of school-based coronavirus cases have repeatedly found regular cleaning—as part of a broader mitigation plan including hand-washing, ventilation, social distancing, and contact tracing—can allow schools to reopen in-person classes safely even when community infection rates are high. Moreover, studies conducted prior to the pandemic have suggested that maintaining cleaner campuses can reduce student absenteeism, particularly for students with chronic illnesses such as asthma.
Surfaces can become contaminated through droplets spread when a person coughs, sneezes, or even talks loudly. However, studies more recently have suggested COVID-19 is spread more frequently through aerosolized virus particles that are inhaled than through touch contamination. Researchers in the journal Science suggested improving indoor air quality and ventilation in schools may be more important than daily, in-depth surface cleaning to keeping schools virus free.
One December study in the Journal of Allergy and Clinical Immunology in Practice finds that the pandemic has led to a significant rise in the use of cleaning products and worsening asthma attacks, particularly with strong bleach and other disinfectant solutions. (To be effective, the CDC recommends a bleach solution be 5 percent to 9 percent sodium hypochlorite.)
While the December study looked at home disinfection rather than schools, the results suggest school leaders show caution if they ask teachers or students to repeatedly clean desks and other classroom surfaces each day, particularly if they use bleach or other disinfectant wipes. (Separate studies have found higher asthma risk with bleach use occurring four to seven times a week.)
However, a separate study in the journal the Lancet suggests students with asthma may have lower symptoms in schools than at home during the pandemic, because home cleaning is likely taking place in smaller and less well-ventilated areas.
“Improving classroom ventilation will be important overall,” as part of both cleaning and overall COVID-19 mitigation strategies, the authors noted, “but there is a fine balance between opening windows and maintaining thermal comfort, and care must be taken to reduce exposure” to outside allergies and pollution, which can also worsen asthma..