Surfaces can become contaminated with SARS-CoV-2 when someone infected with the virus (who may or may not have COVID-19 symptoms) releases the virus from their body into the environment, for example through coughing, sneezing, vomiting, or defecating.
In healthcare settings, SARS-CoV-2 genetic material was found on 8.9% of 336 sampled surfaces, mostly in individual bed spaces, in a multicentre study conducted in England. In another study (unpublished as of December 18, 2020) 13.1% of 336 sampled hospital surfaces (mostly those in direct contact with patients), were positive for the virus genetic material. In an isolation room occupied by a COVID-19 patient in Singapore, SARS-CoV-2 genetic material was reportedly detected on 87% of 15 room surfaces (including things like bed rails and windows) prior to cleaning. The same study found SARS-CoV-2 genetic material on 60% of 5 bathroom sites (including the toilet bowl, sink and door handle). Other studies have found similar results in healthcare settings (Study 1, Study 2, Study 3, Study 4, Study 5).
In community settings, SARS-CoV-2 genetic material was detected at low concentrations in 8.3% of 346 samples collected from frequently touched surfaces in Somerville (MA, USA), with the highest positive rates on a trash can handle and liquor store door handle (Study 6). The corresponding risk of infection was estimated to be low. Likewise, in another study in Belo Horizonte (Brazil, Study 7), 5.3% of 933 surface samples tested positive for SARS-CoV-2 genetic material, with a majority of those positive samples coming from public benches at bus stops or squares. These results are consistent with a small-scale investigation in a rural village in Spain (Study 8).
A systematic review of surface contamination studies suggested that laboratories had the highest proportion of surfaces testing positive for SARS-CoV-2 genetic material (Study 9). Across all settings, masks and eating utensils used by COVID-19 patients were most commonly contaminated with the virus, followed by electronic equipment (see table below).
Overall, while SARS-CoV-2 transmission via surfaces is possible, the scientific evidence available to date suggests that the primary transmission route for SARS-CoV-2 is airborne (as outlined in this Lancet comment) and that contaminated surfaces present a low risk (as noted in this Science Brief by the US CDC).