SARS-CoV-2 RNA detection in the air and on surfaces in the COVID-19 ward of a hospital in Milan, Italy

Abstract
The COVID-19 outbreak has rapidly progressed worldwide finding the health system, scientists and society unprepared to face a little-known, fast spreading, and extremely deadly virus. Italy is one of the countries hardest hit by the pandemic, resulting in healthcare facilities bearing heavy burdens and severe restrictive measures. Despite efforts to clarify the virus transmission, especially in indoor scenarios, several aspects of SARS-CoV-2 spread are still rudimentary. This study evaluated the contamination of the air and surfaces by SARS-CoV-2 RNA in the COVID-19 isolation ward of a hospital in Milan, Italy. A total of 42 air and surface samples were collected inside five different zones of the ward including contaminated (COVID-19 patients’ area), semi-contaminated (undressing room), and clean areas. SARS-CoV-2 RNA detection was performed using real time reverse transcription polymerase chain reaction. Overall, 24.3% of swab samples were positive, but none of these were collected in the clean area. Thus, the positivity rate was higher in contaminated (35.0%) and semi-contaminated (50.0%) areas than in clean areas (0.0%; P<0.05). The most contaminated surfaces were hand sanitizer dispensers (100.0%), medical equipment (50.0%), medical equipment touch screens (50.0%), shelves for medical equipment (40.0%), bedrails (33.3%), and door handles (25.0%). All the air samples collected from the contaminated area, namely the intensive care unit and corridor, were positive while viral RNA was not detected in either semi-contaminated or clean areas. These results showed that environmental contamination did not involve clean areas, but the results also support the need for strict disinfection, hand hygiene and protective measures for healthcare workers as well as the need for airborne isolation precautions.