COVID-19 on Surfaces: Examining the Known Unknowns

Months into the COVID-19 pandemic, knowledge gaps remain about how fomites contribute to SARS-CoV-2 transmission, a researcher said.

A systematic review of research on SARS-CoV-2 on surfaces found 78 articles, the majority of which centered around healthcare settings, but there remains an inability to align what is known about surfaces contaminated by the virus with survivability of SARS-CoV-2 on those surfaces, reported Gabrielle String, PhD, of Tufts University in Medford, Massachusetts.

Not only that, but researchers have yet to match this information to whether or not disinfection of surfaces is effective, she said at a late-breaking presentation at the virtual annual meeting of the American Society of Tropical Medicine & Hygiene.

String noted that WASH interventions (water, sanitation, and hygiene) are key to preventing disease transmission during outbreaks, and researchers examined existing research about how they could interrupt the transmission of SARS-CoV-2.

They downloaded literature from two databases: the NIH COVID-19 Portfolio and the CDC COVID-19 Research Articles Downloadable Database and found 78 articles that met their criteria about surface contamination, stability, or disinfection of SARS-CoV-2.

In the 35 studies focusing on surfaces by settings, healthcare surfaces were sampled more than any other setting. The highest proportion of positive surfaces were found in a patient's room, non-household accommodations, and laboratories.

Within the 25 studies with samples from patients' rooms, viral RNA was detected on cups (one out of two positives); soft bedding, such as the pillow, sheets, and covers (17 of 42 positives); and hard bedding, such as the bed handle and headboard (two of five positives).

In the five studies examining non-household accommodations, viral RNA was found on all five samples of wooden chopsticks, patient personal protective equipment (two of three positives), and electronic high-touch surfaces, like the computer mouse and the TV (seven of 16 positives).

Seven studies examined specifically how long SARS-CoV-2 persists on surfaces, with 29 unique surfaces tested. Nine studies examined stainless steel and plastics, but glass, nitrile gloves, and aluminum were also examined.

String noted there was a "range of temperatures and humidities" tested on the surfaces within the studies, but the key takeaway was "as temperature and humidity increase, the half-life of SARS-CoV-2 decreased."

Twenty different disinfectants against SARS-CoV-2 were examined, the large majority of which were suspension tests (89%). The nine studies focusing on suspension tests found reduction of SARS-CoV-2 was dependent on dosage and contact time.

"Some disinfectants, such as heat and a long contact time with hand sanitizer had almost a 6 log reduction," she said.

In the three studies focusing on disinfection of SARS-CoV-2 on surfaces, simulated sunlight for greater than 60 minutes and UV-C radiation greater than 2 minutes resulted in a greater than 4 log reduction, String said, but cautioned that results were limited as of July.

She also noted the heterogeneity of the studies, with variations in concentrations and contact times, and that researchers struggled to compare data where collection techniques varied.

"We need to ensure we standardize some of these [testing] methods ... so we can compare data more broadly," String said.

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