Cite this article as: Liu, Y. et al. Aerodynamic analysis of SARS-CoV-2 in two Wuhan hospitals. Nature https://doi.The ongoing COVID-19 outbreak has spread rapidly on a global scale. While the transmission of SARS-CoV-2 via human respiratory droplets and direct contact is clear, the potential for aerosol transmission is poorly understood 1-3 . This study investigated the aerodynamic nature of SARS-CoV-2 by measuring viral RNA in aerosols in different areas of two Wuhan hospitals during the COVID-19 outbreak in February and March 2020. The concentration of SARS-CoV-2 RNA in aerosols detected in isolation wards and ventilated patient rooms was very low, but it was elevated in the patients' toilet areas. Levels of airborne SARS-CoV-2 RNA in the majority of public areas was undetectable except in two areas prone to crowding, possibly due to infected carriers in the crowd. We found that some medical staff areas initially had high concentrations of viral RNA with aerosol size distributions showing peaks in submicrometre and/or supermicrometre regions, but these levels were reduced to undetectable levels after implementation of rigorous sanitization procedures. Although we have not established the infectivity of the virus detected in these hospital areas, we propose that SARS-CoV-2 may have the potential to be transmitted via aerosols. Our results indicate that room ventilation, open space, sanitization of protective apparel, and proper use and disinfection of toilet areas can effectively limit the concentration of SARS-CoV-2 RNA in aerosols. Future work should explore the infectivity of aerosolized virus.

Background: Since being first reported in Wuhan, China, in December 8, 2019, the outbreak of the novel coronavirus, now known as COVID-19, has spread globally. Some case studies regarding the characteristics and outcome of patients with COVID-19 have been published recently. We conducted a meta-analysis to evaluate the risk factors of COVID-19. Methods: Medline, SinoMed, EMBASE, and Cochrane Library were searched for clinical and epidemiological studies on confirmed cases of COVID-19. Results: The incidence of fever, cough, fatigue, and dyspnea symptoms were 85.6 % (95CI 81.3-89.9 %), 65.7 % (95CI 60.1-71.4 %), 42.4 % (95CI 32.2-52.6 %) and 21.4 % (95CI 15.3-27.5 %). The prevalence of diabetes was 7.7 % (95CI 6.1-9.3 %), hypertension was 15.6 % (95CI 12.6-18.6 %), cardiovascular disease was 4.7 % (95CI 3.1-6.2 %), and malignancy was 1.2 % (95CI 0.5-1.8 %). The complications, including ARDS risk, ranged from 5.6-13.2 %, with the pooled estimate of ARDS risk at 9.4 %, ACI at 5.8 % (95CI 0.7-10.8 %), AKI at 2.1 % (95CI 0.6-3.7 %), and shock at 4.7 % (95CI 0.9-8.6 %). The risks of severity and mortality ranged from 12.6 to 23.5% and from 2.0 to 4.4 %, with pooled estimates at 18.0 and 3.2 %, respectively. The percentage of critical cases in diabetes and hypertension was 44.5 % (95CI 27.0-61.9 %) and 41.7 % (95CI 26.4-56.9 %), respectively. Conclusion: Fever is the most common symptom in patients with COVID-19. The most prevalent comorbidities are hypertension and diabetes which are associated with the severity of COVID-19. ARDS and ACI may be the main obstacles for patients to treatment recovery. The case severe rate and mortality is lower than that of SARS and MERS.

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.

We report a comparative study of the structure and chemistry of methyl-terminated n-alkanethiol selfassembling monolayers (SAMs) formed from liquid and vapor phases. Three different SAMs are considered: Au/ HS(CH2)"CH3, n = 5, 11, and 15. Liquid-phase-deposited films were prepared by exposure of Au substrates to dilute ethanol solutions of the n-alkanethiols followed by ethanol rinsing, and vapor-phase-deposited SAMs were prepared by exposure of the Au surface to 10%-of-saturation n-alkanethiol vapors followed by N2 purging, which removes loosely bound n-alkanethiol molecules from the surface. The matrix of six organic surfaces was studied by FTIR external reflectance spectroscopy (FTIR-ERS), ellipsometry, and cyclic voltammetry, which provide information about the average structure of the SAMs, and a newly developed scanning tunneling microscope (STM)-based method, which provides information about individual SAM defect structures. FTIR-ERS and ellipsometry indicate no detectable differences between liquid-and vapor-phase-deposited SAMs. Data obtained using cyclic voltammetry and STM show that the barrier properties of SAMs depend on the ambient phase from which the SAM assembles, the length of the rt-alkanethiol, and the chemical nature of the molecular probe used to evaluate the monolayer structure. For example, vapor-phase-deposited Au/HS(CH2)nCH3 SAMs are better CN mass-transfer barriers than their liquid-phasedeposited analogs. However, Au/HS(CH2)]5CH3 SAMs are better CNbarriers when they are formed from the liquid phase. In contrast, Au/HS(CH2)nCH3 SAMs prepared from either phase present nearly identical barriers to electron exchange between the Au surface and solution-phase Ru(NH3)63+. STM reveals some of the nanostructural details of SAMs and confirms that individual defects govern their barrier properties.

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The tip of a scanning tunneling microscope was used to fabricate geometrically well-defined structures within organized, self-assembled monolayer resists that have critical dimensions ranging from 60 nm to 5 pm. To achieve nanometer-scale lithography, a Au(lll) substrate was coated with a self-assembled monolayer of HS(CH2)i7CH3, which functions as an ultrathin (~2.5 nm) resist, and then the resist was etched by an STM tip. This treatment results in windowlike features that penetrate the organic monolayer. Nanolithographically defined features have been characterized by scanning tunneling microscopy, scanning electron microscopy, and electrochemical methods. For example, since mass and electron transfer to the conductive Au substrate are blocked by the monolayer everywhere except in the STM-etched regions, the windows serve as ultramicroelectrodes. The limiting current that results from radial diffusion of a bulkphase redox species to the etched window is in close agreement with that predicted by theory.

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