Aerodynamic Characteristics and RNA Concentration of SARS-CoV-2 Aerosol in Wuhan Hospitals during COVID-19 Outbreak

Yuan Liu; Zhi Ning; Yu Chen; Ming Guo; Yingle Liu; Nirmal Kumar Gali; Li Sun; Yusen Duan; Jing Cai; Dane Westerdahl; Xinjin Liu; Kin-fai Ho; Haidong Kan; Qingyan Fu; Ke Lan

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] [2] [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.