researchers reported that titers of viable virus remained unchanged after six hours of incubation . Viral titers were decreased by 3.5 orders of magnitude after 24 hours , and < 100 virus particles were retrieved at days 2 and 3 . On metal coupons , a faster reduction of four orders of magnitude was observed after six hours of incubation , and similar levels of viable virus were detected at 24 hours . A further decrease in viability on metal surfaces was detected at days 2 and 3 . No viable virus was recovered from plastic or metal coupons after four to 14 days of incubation .
The researchers next determined the viral stability on surfaces at increased temperatures . The viability of SARS-CoV-2 on plastic coupons was unaffected for at least 30 minutes at 40 degrees C , while a minor reduction of one order of magnitude in viral viability was obtained after one hour . An additional one order of magnitude reduction in virus titers was observed after two to three hours of incubation . After incubation at 50 degrees C of 10 to 20 minutes , viral titers were further reduced by one order of magnitude , and an additional order of magnitude was achieved by extending the incubation time to 30 minutes . After 20 minutes of incubation at 60 degrees C and 10 to 30 minutes at 70 degrees C no viable particles were detected .
Ben-Shmuel , et al . ( 2020 ) also tested viral shedding in environment samples collected from patients ’ rooms in the two hospital isolation units ; in non-ventilated patients ’ rooms , viral RNA was recovered from 9 / 21 of sampled surfaces ( 43 percent ), mostly on floors , bedside tables , faucet handles and patients ’ personal belongings ( e . g ., eyeglasses and a walker ). A higher proportion of contaminated surfaces was detected in mechanically ventilated patients ’ rooms ( 13 / 18 , 72 percent ). Contaminated surfaces included mainly bed rails , ventilator touch screens , staff computer accessories and faucet handles . Viral RNA was detected on only one of seven mobile phones . Using an air sampler , the researchers detected viral RNA in one of one sample in a ventilated patients ’ room , compared to none of three samples taken in non-ventilated patients ’ rooms , and one out of two samples was positive for RNA at the nursing station and in the doffing area . There were differences between the levels of contamination between the two hospitals ; only six out of 23 samples ( 26 percent ) in Hospital A were positive , with an average cycle threshold ( CT ) value of 37.9 , contrasting with Hospital B which had 23 out of 32 samples positive ( 72 percent ) and an average CT value of 34 . Although viral RNA could be detected in 29 / 55 environmental samples ( 51 percent ), the researchers report that they could not propagate any viable virus from any of the samples in Vero-E6 cultured cells .
The researchers concluded that , “ Despite prolonged viability of SARS-CoV-2 in controlled conditions , aerosol or indirect transmission from inanimate surfaces around hospitalized or quarantined COVID-19 patients is not supported by the data presented in this study . In healthcare settings , infection prevention and control should focus mainly on prevention of direct face-to-face transmission and droplet protection . Fomite transmission may still be a possibility with heavily contaminated surfaces around patients during their most contagious stages of infection , and in closed and crowded environments .”
Cleaning and disinfection shortfalls have been implicated in infections caused by other human coronavirus ( e . g ., SARS-CoV , MERS-CoV ) and epidemiologically important pathogens , as well as in potential healthcare-associated transmissions via fomites . As Kanamori and Rutala , et al . ( 2017 ) explain , “ The bundle approach
to support best practice of environmental hygiene comprise creating policies and procedures of environmental cleaning / disinfection ; educating healthcare and environmental service staff ; monitoring compliance of cleaning with feedback ; choosing cleaning / disinfecting products properly ; and applying a ‘ no-touch ’ technology into room decontamination . Recently , the researching effective approaches to cleaning in hospitals ( REACH ) study , a multicenter randomized trial demonstrated that an environmental cleaning bundle , consisting of five components of communication , training , audit , product , and technique , improved thoroughness of routine and discharge cleaning at frequent-touch points and led to a significant reduction in vancomycin-resistant enterococci infections .”
Kanamori ( 2020 ) advises that environmental hygiene is imperative , despite the scuffle over the issue of SARS-CoV-2 contamination on fomites : “ Until the risk of fomite transmission of SARS-CoV-2 in the healthcare is elucidated with further high-quality research on its survival and contamination as well as clinical evidence on fomite transmission , we should make efforts to improve cleaning / disinfection practice of environmental surfaces and
“ Despite prolonged viability of SARS-CoV-2 in controlled conditions , aerosol or indirect transmission from inanimate surfaces around hospitalized or quarantined COVID-19 patients is not supported by the data presented in this study .”