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The current outbreak of coronavirus disease 2019 (COVID-19) has spread rapidly on a global scale. Although it is clear that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is transmitted through human respiratory droplets and direct contact, the potential for aerosol transmission is poorly understood. Here we investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the outbreak of COVID-19 in February and March 2020.

We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions that showed peaks in the supermicrometer regions; however, these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. The infectivity of the virus has not been detected but we propose that SARS-CoV-2 may be transmitted through aerosols. Our results indicate that room ventilation, sanitization, and disinfection of toilet areas can limit the concentration of SARS-CoV-2 RNA in aerosols.

The ongoing outbreak of COVID-19, which has been reported in 206 countries has resulted in deaths globally. The World Health Organization (WHO) has declared the COVID-19 outbreak a pandemic and global public health emergency. A retrospective study conducted after the SARS epidemic, which was caused by SARS-CoV in Hong Kong in 2003 suggested that airborne spread may have had an important role in the transmission of SARS.

We analysed the occurrence of airborne SARS-CoV-2 and its aerosol deposition at 30 sites in two designated hospitals and public areas in Wuhan, China, and then quantified the copy counts of SARS-CoV-2 in aerosol samples using a robust droplet-digital-PCR-based detection method (ddPCR). Both hospitals are used for the treatments of patients with COVID-19 during the outbreak; however, each hospital has unique characteristics that serve different purposes. Renmin Hospital of Wuhan University (hereafter, Renmin Hospital) is representative of grade-A tertiary hospitals that have been designated for the treatment of patients with severe symptoms of COVID-19. By contrast, Wuchang Fangcang Field Hospital (hereafter, Fangcang Hospital) is representative of the makeshift field hospitals that were converted from indoor sports facilities or exhibition centres to quarantine and treat patients with mild symptoms.

Very low or undetectable concentrations of airborne SARS-CoV-2 were found in most of the patient areas of Renmin Hospital. The coronary care units and ward rooms of Renmin Hospital limit the airborne transmission of SARS-CoV-2. The highest concentration in patient areas was observed inside a patient mobile toilet room at Fangcang Hospital, which is a temporary single toilet room, without ventilation. Airborne SARS-CoV-2 may come from either the patient’s breath or the faeces or urine of a patient.

The results of this study have implications for the prevention of infection of the public and protection of medical staffs. We call for , attention to the ventilation and sterilization of toilets; protection measures for the public ; the sanitization of high-risk areas in the hospital to limit the transmission of airborne SARS-CoV-2; and the surface sanitization of the apparel before the equipment is taken off to reduce the risk of infection for medical staffs.