Contamination by SARS-CoV-2 from a symptomatic patient

Air, surface environmental, and personal protective equipment contamination by SARS-CoV-2 from a symptomatic patient. Jefferson T, Heneghan C.

Published on July 23, 2020

Reference Ong SWX, Tan YK, Chia PY, Lee TH, Ng OT, Wong MSY, et al. Air, surface environmental, and personal protective equipment contamination by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) from a symptomatic patient. JAMA. 2020;323(16):1610-2. 2020
Study type
Country Singapore
Setting Hospital
Funding Details National Medical Research Council (NMRC) Seed Funding Program (TR19NMR119SD) and internal funds from DSO National Laboratories, Singapore
Transmission mode Droplet, fomites, close contact, orofecal

Bottom Line

Severity of symptoms is no guide to intensity of viral shedding but all post cleaning samples were negative and current decontamination measures appeared sufficient.

Evidence Summary

There was extensive environmental contamination by one SARS-CoV-2 “patient C” with mild upper respiratory tract involvement (the other two were classified as having moderate symptoms). 

The PCR cycle threshold for patient C was lower than the others pointing to a higher viral load.

The toilet bowl (seat and inner surface) and sink samples were positive, suggesting that viral shedding in stool could be a potential route of transmission. Post-cleaning samples were negative, suggesting that current decontamination measures were sufficient.

What did they do?

The study ran from 24th January to 4th February 2020 and involved sampling in the physical areas around three COVID-19 patients at the Singapore dedicated SARS-CoV-2 outbreak center. The patients were in airborne infection isolation rooms with constant ventilation (12 air exchanges per hour) and each room had an anteroom and a bathroom. Samples were taken at 26 sites and from PPE of study physicians exiting the patient rooms. Air was sampled on two days in the room and anteroom.

Sampling was conducted on five days over a 2-week period. One patient’s room was sampled before routine cleaning and two patients’ after cleaning. Cleaning of high touch areas was done twice daily. The floor was cleaned once a day. All cleaning was done using chlorine based products. 

The authors then correlated timing of cleaning, percentage positivity and clinical symptoms of the patients.

Study reliability

The report is a letter to the editor with a small denominator and appears to be relating to three  patients in three  rooms, although the text is not clear on this. Viral culture was not undertaken, so we do not know whether the PCR positive materials were infectious. The authors also comment on the relative small quantity of air that was sampled.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No Unclear Yes Yes

What else should I consider?

The results of this study need replication.

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.