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
Transmission Dynamics of COVID-19
||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
||National Medical Research Council (NMRC) Seed Funding Program (TR19NMR119SD) and internal funds from DSO National Laboratories, Singapore
||Droplet, fomites, close contact, orofecal
Severity of symptoms is no guide to intensity of viral shedding but all post cleaning samples were negative and current decontamination measures appeared sufficient.
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.
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
What else should I consider?
The results of this study need replication.
About the authors
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, epidemiologist.