COVID-19: Toilets dominate environmental detection of SARS-CoV-2 in a hospital

COVID-19: Toilets dominate environmental detection of SARS-CoV-2 in a hospital. Jefferson T, Heneghan C.

Published on July 6, 2020

Reference Ding Z, Qian H, Xu B, Huang Y, Miao T, Yen H-L, et al. Toilets dominate environmental detection of SARS-CoV-2 virus in a hospital.  medRxiv 2020.04.03.20052175 2020
Study type
Country China, Nanjing
Setting Infectious diseases hospital
Funding Details Non reported
Transmission mode Orofecal
Exposures Hospital, Toilet Surfaces

Bottom Line

Of 107 surface samples (37 from toilets, 34 from other surfaces in isolation rooms and 36 from other surfaces outside isolation rooms). Four samples were positive (2 two ward door door-handles, one bathroom toilet toilet-seat cover and one bathroom door door-handle). Three were weakly positive from a bathroom toilet seat, one bathroom washbasin tap lever and one bathroom ceiling exhaust louvre. One of the 46 corridor air samples was weakly positive.

Evidence Summary

Airflow pattern was found to lead from the corridor to each isolation room, and subsequently to the exhaust via the bathroom.

The paper has a very clear colour-coded figure showing the timeline of onset and hospitalisation dates and the sampling dates of the events in the isolation rooms containing beds 2 and 3, beds 16-18, beds 31 and 32, and bed 55, and their 10 patients. 

The sampling dates on which positive samples were detected are also shown by a red tick. In each room, a patient and his/her bed are shown in the same colour. Of the 107 surface samples, seven were positive:  from inside the door -handle of the isolation room containing beds 16, 17, and 18 the toilet seat in the same isolation room the inside door -handle of the isolation room containing beds 2 and 3 the toilet-seat cover (lower surface) in the isolation room containing a bed, the bathroom tap-lever of the same room the bathroom door -handle of the same room and the exhaust air-grille surface in the bathroom of the same room. Three weakly positive samples were from corridor air.

The figure shows a summary of the location of the samples taken in the isolation rooms. The red circles indicate positive samples.

What did they do?

The study was carried out by random sampling in 3-bed isolation rooms of the COVID-19 designated infectious diseases hospital Nanjing, China.

Environmental sampling was also carried out in four isolation room s, a nursing station, a corridor, an air-conditioning system and other spaces in the airborne infectious-disease zone on the fifth floor of the hospital. 

The sampling was conducted throughout February 2020 and was extended to the roof air exhaust of the hospital. Sampling procedures are described accurately and the air sampler was twice quarantined despite wearing full PPE. 

Airflow was also assessed between 4th and 5th floors in the building using a smoke tracer.

Study reliability

The study is very well described and convincing. Meticulous work gives credible results. No comment on the viability of isolates is reported.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes N/A Yes Yes Yes

What else should I consider?

This study needs replicating but fits in well with the growing body of evidence on the importance of contact transmission.

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Tom Jefferson

Tom Jefferson, epidemiologist.