The researchers concluded that despite prolonged viability of
SARS-CoV-2 under laboratorycontrolled conditions , uncultivable viral contamination of inanimate surfaces might suggest low feasibility for indirect fomite transmission .
• risk assessments analyze all three transmission pathways . For example , Jones ( 2020 ) models the risk of occupationally acquired Corona Virus Disease 2019 ( COVID-19 ) infection among healthcare personnel . In this simulation model of contact , droplet , and airborne transmission , Jones ( 2020 ) includes a virus inactivation rate on hands three orders of magnitude higher than on environmental surfaces . Jones ( 2020 ) finds that fomite transmission risk amounts to only 6.9 percent of the total infection risk . Therefore , it appears that virus inactivation on human hands could be a significant bottleneck , limiting fomite transmission risk of enveloped respiratory viruses .
As Weber and Stilianakis ( 2020 ) emphasize , “ While there are lively debates about the role of airborne transmission of influenza and SARS-CoV-2 and on how and whether airborne transmission should be demarcated from droplet transmission ( Drossinos and Stilianakis 2020 ), the role of fomite transmission is rarely fundamentally questioned . However , many components of this pathway remain underexplored in particular what we see as a crucial ‘ missing link ’ — respiratory virus inactivation on human skin .”
Kanamori ( 2020 ) asserts that , “ Experimental studies have reported prolonged survival of SARS-CoV-2 ) on inanimate surfaces and objects under laboratory conditions ( e . g ., a large inoculum of 107 virus particles on a small surface ). Extrapolating these findings into a real-life situation of the community may lead to an exaggerated risk of fomite transmission . Despite no published studies on survival of viable SARS-CoV-2 on surfaces in actual patient-care rooms , there are increasing studies that report contamination of environmental surfaces and shared objects with SARS-CoV-2 RNA .”
For example , Ye , et al . ( 2020 ) examined environmental contamination in patient-care areas , including the intensive care unit ( ICUs ), isolation wards , and emergency department caring for COVID-19 patients with multiple symptoms and severity . Of 626 environmental samples collected during the ongoing outbreak , 85 ( 13.6 percent ) were positive for SARS-CoV-2 RNA by reverse transcription polymerase chain reaction ( RT-PCR ), with 31.9 percent ( 22 / 69 ) in the ICU and 13.9 percent ( 60 / 431 ) in hospital objects , demonstrating frequent contamination of the healthcare environment with SARS-CoV-2 RNA .
Kanamori ( 2020 ) cautions that these results from environmental contamination studies should be assessed and interpreted carefully , since the contamination level of the healthcare environment with SARS-CoV-2 RNA is impacted by multiple factors , including COVID-19 patients ’ status , hospital areas , sampling situation , cleaning and disinfection status in sampling , cleaning and disinfection practice , environmental sampling methods , detection methods of SARS-CoV-2 , type of the contaminated healthcare environment , and contamination rate .
Additionally , as Kanamori ( 2020 ) notes , “ Environmental contamination studies evaluated by both
RT-PCR and viral culture demonstrated that viable SARS-CoV-2 was not detected in samples from environmental surfaces despite presence of environmental contamination with SARS-CoV-2 RNA .”
A critical point is that virus detection does not necessarily represent an infectious dose of SARS-CoV-2 .
For example , Colaneri , et al . conducted environmental surface sampling after twice-daily cleaning with sodium hypochlorite at a concentration of 1,000 ppm at various sites in potentially contaminated areas of an infectious disease emergency unit occupied by patients with respiratory symptoms receiving continuous positive airway pressure ( CPAP ). They described that two of 26 environmental samples ( 7.7 percent ) obtained from the plastic of the CPAP helmet close to the patient ’ s airways with specific filters was positive for SARS-CoV-2 RNA , but viable SARS-CoV-2 was not detected from these environmental samples , suggesting that environmental contamination of SARS- CoV-2 after cleaning / disinfection may be infrequent in healthcare settings .
Kanamori ( 2020 ) asserts that , “ No study has definitively demonstrated fomite transmission via environmental surfaces and objects in healthcare . Although SARS-CoV-2 may be transmitted via direct and indirect contact by touching contaminated surfaces or medical equipment , followed by touching mouth , nose , or eyes , it remains unknown what portion of transmission is attributable to a fomite .”
Let us examine a fomite study under controlled conditions , for contrast .
Ben-Shmuel , et al . ( 2020 ) assessed the infectivity of SARS-CoV-2-contaminating surfaces and objects in two hospital isolation units and a quarantine hotel , with virus stability and infectivity on non-porous surfaces tested under controlled laboratory conditions . In these laboratory-controlled conditions , according to the researchers , SARS-CoV-2 gradually lost its infectivity completely by day 4 at ambient temperature , and the decay rate of viral viability on surfaces directly correlated with increase in temperature . Viral RNA was detected in 29 / 55 surface samples ( 52.7 percent ) and 16 / 42 surface samples ( 38 percent ) from the surroundings of symptomatic COVID-19 patients in isolation units of two hospitals and in a quarantine hotel for asymptomatic and very mild COVID-19 patients . None of the surface and air samples from the three sites ( 0 / 97 ) were found to contain infectious titers of SARS-Cov-2 on tissue culture assay .
The researchers concluded that despite prolonged viability of SARS-CoV-2 under laboratory-controlled conditions , uncultivable viral contamination of inanimate surfaces might suggest low feasibility for indirect fomite transmission .
In their study , surfaces were swabbed with sterile cotton-tipped applicators in an area of 20 × 20 cm , with smaller objects were swabbed entirely . Air sampling was performed using an MD8 air sampler at 50 L / min sampling rate for 20 minutes . On SARS-CoV-2-contaminated plastic coupons , the