Aerosol and surface distribution of SARs-CoV-2 in hospital wards, Wuhan, China
Aerosol and surface distribution of SARs-CoV-2 in hospital wards, Wuhan, China Spencer EA, Heneghan C.,
Published on July 27, 2020
Transmission Dynamics of COVID-19
||Guo ZD, Wang ZY, Zhang SF, et al. Aerosol and surface distribution of Severe Acute Respiratory Syndrome Coronavirus 2 in hospital wards, Wuhan, China, 2020. Emerging Infectious Diseases. 2020 Jul;26(7):1583-1591. DOI: 10.3201/eid2607.200885
||National Major Research & Development Program of China
In a hospital treating COVID-19 patients, SARS-CoV-2 RNA was found widely distributed in surface and air samples.
Contamination was greater in intensive care units (54/124 samples) than general wards (9/114 samples).
A 100% rate of positivity was found on the floor in the pharmacy, where there were no patients.
Half of the samples from the soles of the ICU medical staff shoes tested positive.
The rate of positivity was relatively high for floor swab samples (ICU 7/10; general ward 2/13).
The highest rates were found for computer mice (ICU 6/8; general ward 1/5), followed by trash cans (ICU 3/ 5; general ward 0/8), sickbed handrails (ICU 6/14; general ward 0/12), and doorknobs (general ward 1/12, 8.3%).
SARS-CoV-2 RNA was detected in the air 4 m from patients.
A Layout of the intensive care unit (ICU)
The order of dressing is dressing room 1, dressing room 2, and dressing room 3; the order of undressing in dressing room 4, dressing room 5, and dressing room 6.
The isolation ward of ICU is a large floor space with 15 cubicles (each with a patient bed) along the 2 opposite perimeters. Each cubicle is open to the central open area without any partition.
B and general ward
The order of dressing is dressing room 1, dressing room 2, and dressing room 3; the order of undressing in dressing room 4, dressing room 5, and buffer room 1. The contaminated area of the general ward contains a patient corridor, and the 1-sided cubicles are all enclosed with door access to the corridor.”
Spatial distribution of severe acute respiratory syndrome coronavirus 2 aerosols in isolation wards of the intensive care unit (ICU) and the general ward at Huoshenshan Hospital, Wuhan, China.
- A) The air sampling sites in the ICU were distributed in different regions: near the air outlet (site 1), near the patients (site 2), and around the doctors’ office area (site 3). Orange circles represent sampling sites; blue arrows represent direction of the fresh air flow; and the graded orange arrow and scale bar indicate the horizontal distance from the patient’s head.
- B) In terms of viral aerosol distribution, the space in the ICU was divided into 2 parts: a high-risk area with a 41% rate of virus positivity and a low-risk area with a 13% rate of virus positivity.
- C) The air sampling sites in the general ward were distributed in different regions around the patient (site 1), under the air inlet (site 2), and in the patient corridor.
- D) Viral aerosol distributionL space in the general ward divided into 2 parts: a high-risk area with a 13% rate of virus positivity and a low-risk area with a 0% rate of virus positivity.
What did they do?
Air and surface sample testing of intensive care (15 patients with severe COVID-19) and general ward (24 less severe COVID-19 cases) in Huoshenshan Hospital, Wuhan, China, between 19th February and 2nd March 2020.
Sterile pre-moistened swabs were used to sample the floors, computer mice, trash cans, sickbed handrails, patient masks, personal protective equipment, and air outlets.
Samples of indoor air and the air outlets were taken to detect aerosol exposure.
Quantitative real-time PCR was used to test air and surface samples for the open reading frame (ORF) 1ab and nucleoprotein (N) genes of SARS-CoV-2.
Infectivity of samples is not assessed and we do not know whether any of these positive testing samples pose a viable infection risk.
|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 authors suggest the high contamination of floors is due to gravity and airflow causing most virus droplets to float to the ground, as well as medical staff moving the contamination with their shoes as they walk around. It is unexplained, why three of five COVID-19 patients’ masks tested negative.
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
Dr Elizabeth Spencer; MMedSci, PhD. Epidemiologist, Nuffield Department for Primary Care Health Sciences, University of Oxford.