Cleaning measures can prevent transmission of COVID-19 from surface contamination

This research investigated the extent of environmental contamination and potential transmission of COVID-19 in hospital settings.

Study design

Environmental samples were taken from 26 sites in airborne infection isolation rooms of 3 patients at the dedicated SARS-CoV-2 outbreak center in Singapore. The rooms included anterooms and bathrooms and had 12 air exchanges per hour. Personal protective equipment (PPE) samples from study physicians exiting the patient rooms also were collected. Air sampling was conducted on 2 days in the room, anteroom and outside the room. Real-time reverse transcriptase–polymerase chain reaction (RT-PCR) was used to detect the presence of SARS-CoV-2. Samples were collected on 5 days over a 2-week period. One patient’s room was sampled before routine cleaning and 2 patients’ rooms after routine cleaning.

Outcomes

The samples collected before routine cleaning from 1 patient (patient C) resulted in 13 of 15 (87%) room sites (including air outlet fans) and 3 of 5 (60%) toilet sites (toilet bowl, sink and door handle) returning positive results; anteroom and corridor samples were negative. This patient C had upper respiratory tract involvement with no pneumonia and had 2 positive stool samples for SARS-CoV-2 on RT-PCR despite the absence of diarrhea.

Samples from the other 2 patients’ rooms collected after cleaning were negative. Patient C had greater viral shedding, with a cycle threshold value of 25.69 in nasopharyngeal samples compared with 31.31 and 35.33 in the other 2 patients. Just 1 PPE swab, from the surface of a shoe front, was positive. All other PPE swabs were negative. All air samples were negative.

Limitations

This study was limited by several factors: viral culture was not conducted to demonstrate viability, methodology was inconsistent and the sample size was small. The volume of air sampled represents only a small fraction of total volume, and air exchanges in the room would have diluted the presence of SARS-CoV-2 in the air.

Clinical significance

There was extensive environmental contamination by the patient with mild upper respiratory tract involvement whose samples were taken prior to routine cleaning. Toilet bowl and sink samples were positive, suggesting that viral shedding in stool could be a potential route of transmission. Post-cleaning samples were negative, suggesting current decontamination measures are sufficient. The risk of transmission from contaminated footwear is likely low, as evidenced by negative results in the anteroom and clean corridor. In summary, the spread of SARS-CoV-2 through respiratory droplets and fecal shedding suggests the environment as a potential medium of transmission and supports the need for strict adherence to environmental and hand hygiene.