Low risk of SARS-CoV-2 transmission by fomites in real-life conditions

We read with interest the Comment by Emanuel Goldman¹ highlighting experiments done under controlled laboratory conditions that suggest persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on inanimate surfaces for days, with potential implications for viral transmission.² Yet, at the same time, Goldman laments the absence of real-life studies investigating the infectious potential of SARS-CoV-2 on contaminated inanimate material and patient fomites, particularly in high-risk hospital wards. A study done in a hospital environment showed that most surfaces were contaminated, including air-conditioning vents, bed rails, bedside lockers, and rarely, toilets.³ Of note, environmental surface contamination declined after week 1 of illness, and intriguingly, no surface contamination was detected in intensive care unit (ICU) rooms. A limitation of the study by Chia and colleagues³ is that no attempt was made to culture SARS-CoV-2 from the environmental swabs, which would have helped to understand the significance of SARS-CoV-2 RNA positive samples in terms of infectious potential.

We have done two sequential studies4, 5 seeking to determine on one hand the extent, if any, of contamination of inanimate surfaces in a standard infectious disease ward of a major referral hospital in northern Italy, and on the other hand whether the risk of contamination was higher in emergency rooms and sub-intensive care wards than on ordinary wards. Cleaning procedures were standard. A number of objects and surfaces were swabbed. Remarkably, only the continuous positive airway pressure helmet of one patient was positive for SARS-CoV-2 RNA. More importantly, attempts to culture the positive swabs on Vero E6 cells were unsuccessful,⁵ suggesting that patient fomites and surfaces are not contaminated with viable virus. Our findings suggest that environmental contamination leading to SARS-CoV-2 transmission is unlikely to occur in real-life conditions, provided that standard cleaning procedures and precautions are enforced. These data would support Goldman's point that the chance of transmission through inanimate surfaces is less frequent than hitherto recognised.