Studies on surface and airborne transmission

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It’s been over one year since the novel coronavirus was officially deemed a pandemic, and researchers continue to explore how this disease spreads. The role of the built environment has taken center stage and is perhaps more prominent than ever before in mainstream understanding of infection prevention. We see several new studies on this topic in the recent additions to The Center for Health Design’s Knowledge Repository. Four are highlighted here along with other key resources. 

In August 2020, Lednicky and colleagues posted a preprint article sharing their use of a new direct sampling technique to investigate airborne transmission in hospitals. The researchers used air samplers in a patient room of two COVID-19-positive patients. They found viable virus in air samples 7 to 16 feet from the patients, much further than the 6-foot guidance, indicating that the virus traveled in the air as an aerosol particle.  

A systematic literature review by Birgand and colleagues summarized evidence of air contaminated with SARS-CoV-2 RNA close to and far (3 to 16 feet) from patients, but in these cases, few samples contained viable viruses. The review points to evidence around high viral loads in certain areas of the hospital: toilets, bathrooms, staff areas and public hallways. The authors urge careful consideration of their findings around high concentrations in unventilated areas, especially in staff areas where staff temporarily remove their masks to eat or take a break. 

Given the likelihood of airborne transmission, HVAC systems become part of a mitigation strategy. Current guidance from ASHRAE and the American Society for Health Care Engineering (ASHE) includes recommendations for ventilation, filtration and humidification. While limited available evidence for reducing transmission is available for these strategies, particle dilution with clean air supply and quality filters appears to be key. 

Surface transmission has been debated, as well. A literature review by Marquèz and colleagues, as well as a newer study using environmental sampling by Wei and colleagues, continue to suggest surface transmission is plausible. Both papers discuss the evidence around fomites and SARS-CoV-2, with some samples showing viable virus detected on surfaces for up to a few days. The jury is still out on the likelihood of becoming infected from viable COVID-19 on these surfaces. Thankfully, findings seem clear around the success of common chemicals and biocides in deactivating the virus. 

There has been an enormous influx of COVID-19 research over the past year. Conflicting information and changing positions can be confusing. As with any evidence-based practice, we need to work with the best available information we have today, while continuing to push for additional research to inform the best facilities management and design decisions. 

For more information on the health care environment and COVID-19, as well as several other topics related to health care design, visit The Center for Health Design’s Knowledge Repository; and to learn about the latest COVID-19 advisories, visit ASHE's website.

Research used for this column

The following citations from The Center for Health Design’s Knowledge Repository of health care design resources were used by the author when writing this column:

• J. A. Lednicky et al., “Viable SARS-CoV-2 in the Air of a Hospital Room with COVID-19 Patients,” International Journal of Infectious Diseases 100 (2020): 476–82.
• G. Birgand et al., “Assessment of Air Contamination by SARS-CoV-2 in Hospital Settings,” JAMA Network Open 3, no. 12 (2020): e2033232.
• M. Marquès and J. L. Domingo, “Contamination of Inert Surfaces by SARS-CoV-2: Persistence, Stability and Infectivity. A Review,” Environmental Research 193 (2021).
• L. Wei et al., “Contamination of SARS-CoV-2 in Patient Surroundings and on Personal Protective Equipment in a Non-ICU Isolation Ward for COVID-19 Patients with Prolonged PCR Positive Status,” Antimicrobial Resistance & Infection Control 9, no. 1 (2020): 167–71.

About this column

“Design Discoveries” highlights research from The Center for Health Design’s Knowledge Repository, a user-friendly library of health care design resources. This research effort is supported by the American Society for Health Care Engineering, the American Institute of Architects, the Academy of Architecture for Health Foundation and the Facility Guidelines Institute.