Detection of Air and Surface Contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Hospital Rooms of Infected Patients

Background: Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies. Objective: To detect the surface and air contamination by SARS-CoV-2 and study the associated patient-level factors. Design: Cross-sectional study. Setting: Airborne infection isolation rooms (AIIRs) at the National Centre for Infectious Diseases, Singapore. Patients: COVID-19 inpatients with a positive PCR test for SARS-CoV-2 within 72 hours before the environmental sampling. Measurements: Extent of environmental surface contamination in AIIRs of 30 COVID-19 patients by PCR on environmental swabs. The particle size distribution of SARS-CoV-2 in the air was measured using NIOSH air samplers. Results: 245 surface samples were collected from 30 rooms of COVID-19 patients, and air sampling was conducted in 3 rooms. 56.7% of the rooms had at least one environmental surface contaminated, with 18.5% of the toilet seats and toilet flush button being contaminated. High touch surface contamination was shown in ten (66.7%) out of 15 patients in the first week of illness, and three (20%) beyond the first week of illness (p = 0.010). Air sampling of two COVID-19 patients (both day 5 of symptoms) detected SARS-CoV-2 PCR-positive particles of sizes >4 μm and 1-4 μm. In a single subject at day 9 of symptoms, no SARS-CoV-2 PCR-positive particles were detected. Limitations: Viral culture results were not available to assess the viability of the virus contaminating the air and surface. Conclusion: Environmental contamination was detected in rooms with COVID-19 patients in early stages of illness, but was significantly less after day 7 of disease. Under AIIR conditions, SARS-CoV-2 respiratory particles can be detected at sizes 1-4 μm and >4 μm in diameter in the air which warrants further studies.