By: www.biorxiv.org

Abstract

Background: The ongoing outbreak of COVID-19 has spread rapidly and sparked global

concern. While the transmission of SARS-CoV-2 through human respiratory droplets and

contact with infected persons is clear, the aerosol transmission of SARS-CoV-2 has been

little studied.

Methods: Thirty-five aerosol samples of three different types (total suspended particle, size

segregated and deposition aerosol) were collected in Patient Areas (PAA) and Medical Staff

Areas (MSA) of Renmin Hospital of Wuhan University (Renmin) and Wuchang Fangcang

Field Hospital (Fangcang), and Public Areas (PUA) in Wuhan, China during COVID-19

outbreak. A robust droplet digital polymerase chain reaction (ddPCR) method was employed

to quantitate the viral SARS-CoV-2 RNA genome and determine aerosol RNA concentration.

Results: The ICU, CCU and general patient rooms inside Renmin, patient hall inside

Fangcang had undetectable or low airborne SARS-CoV-2 concentration but deposition

samples inside ICU and air sample in Fangcang patient toilet tested positive. The airborne

SARS-CoV-2 in Fangcang MSA had bimodal distribution with higher concentration than

those in Renmin during the outbreak but turned negative after patients number reduced and

rigorous sanitization implemented. PUA had undetectable airborne SARS-CoV-2

concentration but obviously increased with accumulating crowd flow.

Conclusions: Room ventilation, open space, proper use and disinfection of toilet can

effectively limit aerosol transmission of SARS-CoV-2. Gathering of crowds with

asymptomatic carriers is a potential source of airborne SARS-CoV-2. The virus aerosol

deposition on protective apparel or floor surface and their subsequent resuspension is a

potential transmission pathway and effective sanitization is critical in minimizing aerosol

transmission of SARS-CoV-2.

Background

Circulating in China and 94 other countries and territories, the COVID-19 epidemic

has resulted in 103,168 confirmed cases including 22,355 outside mainland China, with

3,507 deaths reported (March 7, 2020). Due to its increasing threat to global health, WHO

has declared that the COVID-19 epidemic was a global public health emergency. The

causative pathogen of the COVID-19 outbreak has been identified as a highly infectious

novel coronavirus which is referred to as the Severe Acute Respiratory Syndrome

Coronavirus 2 (SARS-CoV-2).1-3

The transmission of SARS-CoV-2 in humans is thought to be via at least 3 sources: 1)

inhalation of liquid droplets produced by and/or 2) close contact with infected persons and 3)

contact with surfaces contaminated with SARS-CoV-2.4

 Moreover, aerosol transmission of

pathogens has been shown in confined spaces.5,6 There are many respiratory diseases

spread by the airborne route such as tuberculosis, measles and chickenpox.7,8 A

retrospective cohort study conducted after the SARS epidemic in Hong Kong in 2003

suggested that airborne spread may have played an important role in the transmission of

that disease.9

 At present, there is little information on the characteristics of airborne SARS-CoV-2 containing aerosols, their concentration patterns and behaviour during airborne

transmission due to the difficulties in sampling virus-laden aerosols and challenges in their

quantification at low concentration. Such a lack of understanding limits effective risk

assessment, prevention and control of COVID-19 disease outbreaks. This study on airborne

SARS-CoV-2 was conducted in different areas inside two hospitals and public areas in

Wuhan, China, the epicenter city during the initial disease outbreak. We aimed to 1) quantify

the concentrations of airborne SARS-CoV-2 both inside the hospitals and in outdoor public

areas, 2) evaluate the aerodynamic size distributions of SARS-CoV-2 aerosols that may

mediate its airborne transmission, and 3) determine the dry deposition rate of the airborne

SARS-CoV-2 in a patient ward room.

Read more: https://www.biorxiv.org/content/10.1101/2020.03.08.982637v1.full.pdf