Which of the various low and high-tech measures proposed to mitigate SARS-CoV-2 transmission, from hand hygiene to air cleaners, actually work? A new study gives practical tools for assessment and insights into their effectiveness.
The COVID-19 pandemic has brought about numerous challenges in controlling the transmission of the SARS-CoV-2 virus. To combat this, various measures, both low and high-tech, have been suggested and implemented to reduce transmission risks. This review discusses these measures and practical tools that can assess their effectiveness.
“High technology and low technology measures to reduce risk of SARS-CoV-2 transmission” recently published in the American Journal of Infection Control1 authored by Curtis J. Donskey, MD.
Hand Hygiene: One of the simplest and most effective ways to prevent viral transmission is proper hand hygiene. Regular handwashing with soap and water for at least 20 seconds is recommended. Additionally, hand sanitizers with at least 60% alcohol content can be used when soap and water are not available.
Ventilation: Improving ventilation in indoor spaces is crucial. Opening windows and using fans can help dilute indoor air and reduce the concentration of infectious aerosols. Monitoring carbon dioxide levels can be a useful tool to assess ventilation adequacy.
Donskey wrote, “The concentration of carbon dioxide in outdoor air is approximately 400 parts per million (ppm) versus approximately 40,000 ppm in exhaled breath. Thus, carbon dioxide levels rise in occupied spaces that are inadequately ventilated for the number of people present. Handheld devices that cost less than $100 are commercially available and easy to use. The CDC has recommended that carbon dioxide levels above 800 ppm in buildings be considered an indicator of suboptimal ventilation requiring intervention.”
Donskey told Infection Control Today (ICT), "The pandemic has highlighted the importance of ventilation. However, the lack of practical tools to assess ventilation has been a limitation of the pandemic response. How do people know if they need to take steps to improve ventilation if they can’t identify areas where improvement is needed? We have found that simple tools like carbon dioxide monitoring (ie carbon dioxide from breathing builds up when ventilation is inadequate for the number of people in an occupied area) and measurements of clearance of 5% sodium chloride aerosol particles can be very useful. For example, in response to evidence of transmission of SARS-CoV-2 in patient transport vans, we used these tools to show that ventilation was inadequate and identified simple measures to improve ventilation (ie open windows or run the fans continuously to maintain airflow). These tools can also be used to provide healthcare personnel with reassurance that ventilation is adequate in their work area."
Masks: The use of masks, particularly high-filtration masks like N95 respirators, can significantly reduce the spread of respiratory droplets containing the virus. Proper mask-wearing and fit are essential.
Plexiglass Barriers: Plexiglass barriers have been employed in various settings, such as checkout counters and between seats on public transport. While they may provide some protection, their effectiveness depends on factors like airflow and proper installation. “However, little evidence is available regarding the impact of barriers in real-world settings,” Donskey wrote. “An intervention that included physical barriers and universal masking was associated with a significant reduction in COVID-19 cases in meat processing facilities, but placing barriers between students was not associated with a reduction in COVID-19 in schools in Georgia.2 Moreover, there is concern that barriers that are not carefully installed have the potential to hinder good ventilation resulting in increased aerosol exposure.”
Oral and Nasal Antiseptics: These antiseptics have been suggested to reduce the viral load in individuals with COVID-19, potentially reducing transmission. However, more research is needed to establish their real-world efficacy.
Portable Air Cleaners: These devices, equipped with high-efficiency particulate air (HEPA) filters, can help improve indoor air quality by capturing aerosol particles, including viruses. They are especially useful when adequate natural ventilation is not possible.
Air Cleaning Technologies: Some technologies release reactive oxygen species, hydroxyl radicals, or hydrogen peroxide gas to inactivate viral particles in the air. However, further studies, including clinical trials, are needed to confirm their efficacy and safety. One tool is ultraviolet germicidal irradiation (UVGI).
“UVGI is effective for inactivation of SARS-CoV-2 and other respiratory viruses in air," Donskey wrote. "The CDC recommends considering the use of UVGI as a supplemental treatment to inactivate SARS-CoV-2 only when other options for increasing room ventilation and filtration are limited. UVGI can be provided as upper-room UVGI fixtures that provide a disinfection zone of UV above the height of people in the room or as in-duct UVGI systems that kill viruses in central ventilation systems. Upper-room UVGI can be considered in areas likely to include sick people (eg, school nurse's office), in spaces where people must remove masks (eg, cafeterias, restaurants), or in crowded spaces. For upper-room UVGI, the ceiling must be at least 8 feet high."
Assessing Transmission Risk: Practical tools can aid in assessing ventilation and transmission risk. Carbon dioxide monitoring can indicate the adequacy of ventilation by measuring the concentration of exhaled CO2, which can reflect indoor air quality. Devices that release smoke or condensed moisture fog can visualize airflow patterns and assess the effectiveness of ventilation measures.
While some low-tech measures like hand hygiene, ventilation, and mask-wearing are likely to be helpful in reducing transmission, others, like plexiglass barriers and oral/nasal antiseptics, require more substantial evidence. High-tech measures like portable air cleaners and air cleaning technologies can be valuable in settings where natural ventilation is limited.
Donskey told ICT, "One measure that I did not comment on in the article is environmental cleaning. Environmental cleaning was downplayed as “hygiene theater” as evidence accumulated suggesting that the environment plays a relatively minor role in transmission of SARS-CoV-2.
"However, I think it is important that we don’t generalize the findings for COVID-19 to all respiratory viruses. There is good evidence that contaminated fomites can transmit non-enveloped cold viruses and that RSV can be transmitted from contaminated surfaces."