Evaluating infection risks in buses based on passengers' dynamic temporal and typical spatial scenarios: A case study of COVID-19.

Conventional buses, as an indispensable part of the urban public transport system, impose cross-infection risks on passengers. To assess differential risks due to dynamic staying durations and locations, this study considered four spatial distributions (i = 1-4) and six temporal scenarios (j = 1-6) of buses. Based on field measurements and a risk assessment approach combining both short-range and room-scale effects, risks are evaluated properly. The results showed that temporal asynchrony between infected and susceptible individuals significantly affects disease transmission rates. The Control Case assumes that infected and susceptible individuals enter and leave synchronously. However, ignoring temporal asynchrony scenarios, i.e., the Control Case, resulted in overestimation (+30.7 % to +99.6 %) or underestimation (-15.2 % to -69.9 %) of the actual risk. Moreover, the relative difference ratios of room-scale risks between the Control Case and five temporal scenarios are impacted by ventilation. Short-range risk exists only if infected and susceptible individuals have temporal overlap on the bus. Considering temporal and spatial asynchrony, a more realistic total reproduction number (R) can be obtained. Subsequently, the total R was assessed under five temporal scenarios. On average, for the Control Case, the total R was estimated to be +27.3 % higher than j = 1, -9.3 % lower than j = 2, +12.8 % higher than j = 3, +33.0 % lower than j = 4, and + 77.6 % higher than j = 5. This implies the need for a combination of active prevention and real-time risk monitoring to enable rigid travel demand and control the spread of the epidemic.

Formation and toxicity contribution of chlorinated and dechlorinated halobenzoquinones from dichlorophenols after ozonation.

Halobenzoquinones (HBQs) are a class of disinfection byproducts with high cytotoxicity and potential carcinogenicity, which have been widely detected in chlorination of drinking water and swimming pool water. However, to date, the formation of HBQs upon ozonation and the HBQ precursors have been overlooked. This study investigated the formation of chlorinated and dechlorinated HBQs from six dichlorophenol (DCP) isomers. The monomeric and dimeric HBQs were identified in all the ozonation effluents, exhibiting 1-100 times higher toxicity levels than their precursors. The sum of detected HBQs intensity had a satisfactory linear relation with the maximum toxic unit (R2 = 0.9657), indicating the primary toxicity contribution to the increased overall toxicity of effluents. Based on density functional theory calculations, when ozone attacks the para carbon to the hydroxyl group of 2,3-DCP, the probability of producing chlorinated HBQs is 80.41 %, indicating that the para carbon attack mainly resulted in the formation of monomeric HBQs. 2,3-dichlorophenoxy radicals were successfully detected in ozonated 2,3-DCP effluent through electron paramagnetic resonance and further validated using theoretical calculation, revealing the formation pathway of dimeric HBQs. The results indicate that chlorinated phenols, regardless of the positions of chlorine substitution, can potentially serve as precursors for both chlorinated and dechlorinated HBQs formation during ozonation.

The Effectiveness of Symptom Management Theory in Guiding Clinical Practice-A Systematic Review.

Objective: Symptom Management Theory has been extensively used in guiding clinical practice to reduce patients' symptom burden, improve their outcomes and quality of life. However, concerning various participants, settings and methods, the effectiveness of practice and research based on the theory was inconsistent, which hindered the further implementation of this theory in clinical practice. Thus, this study aims to systematically evaluate the effectiveness of the Symptom Management Theory in guiding clinical practice. Methods: Systematic review. An online search of Chinese and English databases, including SinoMed, CNKI, WanFang Library, VIP database, MEDLINE, PubMed, Embase, Web of Science database, and Cochrane Library up to December 2023. This systematic review was conducted in accordance with the Joanna Briggs Institute critical appraisal checklist for randomized controlled trials and controlled clinical trials. The literature appraisal and extraction were independently conducted by two researchers. The third person was consulted if there was any disagreement between the two researchers. Results: A total of 20 articles (15 randomized controlled trials and five controlled clinical trials) were finally included. The overall quality of the articles was high. Additionally, the results showed that symptom management measurements based on the Symptom Management Theory could reduce the severity of patient's symptoms, alleviate their distress, relieve patients' anxiety and depression and improve their quality of sleep and quality of life. Conclusion: The Symptom Management Theory positively influenced clinical symptom management. It could provide theory-based symptom management methods in clinical practice to reduce patients' severity and burden of symptoms, level of anxiety, depression and distress. More high-quality original research should be conducted to further explore the theory's influence in guiding clinical practice in the future.

Redox-directed identification of toxic transformation products during ozonation of aromatics.

The toxicity assessment of transformation products (TPs) formed in oxidative water treatment is crucial but challenging because of their low concentration, structural diversity, and mixture complexity. Here, this study developed a novel redox-directed approach for identification of toxic TPs without the individual toxicity and concentration information. This approach based on sodium borohydride reduction comprised an integrated process of toxicological evaluation, fluorescence excitation-emission matrix characterization, high-resolution mass spectrometry detection, followed by ecological toxicity assessment of identified TPs. The redox-directed identification of primary causative toxicants was experimentally tested for the increased nonspecific toxicity observations in the ozonated effluents of model aromatics. Reduction reaction caused a remarkable decrease in toxicity and increase in fluorescence intensity, obtaining a good linear relation between them. More than ten monomeric or dimeric p-benzoquinone (p-BQ) TPs were identified in the ozonated effluents. The occurrence of the p-BQ TPs was further verified through parallel sodium sulfite reduction and actual wastewater ozonation experiments. In vitro bioassays of luminescent bacteria, as well as in silico genotoxicity and cytotoxicity predictions, indicate that the toxicity of p-BQ TPs is significantly higher than that of their precursors and other TPs. These together demonstrated that the identified p-BQ TPs are primary toxicity contributors. The redox-directed approach facilitated the revelation of primary toxicity contribution, illustrating emerging p-BQs are a concern for aquatic ecosystem safety in the oxidative treatment of aromatics-contaminated wastewater.

Close contact behaviors of university and school students in 10 indoor environments.

Close contact routes, including short-range airborne and large-droplet routes, play an important role in the transmission of SARS-CoV-2 in indoor environments. However, the exposure risk of such routes is difficult to quantify due to the lack of data on the close contact behavior of individuals. In this study, a digital wearable device, based on semi-supervised learning, was developed to automatically record human close contact behavior. We collected 337,056 s of indoor close contact of school and university students from 194.5 h of depth video recordings in 10 types of indoor environments. The correlation between aerosol exposure and close contact behaviors was then evaluated. Individuals in restaurants had the highest close contact ratio (64%), as well as the highest probability of face-to-face pattern (78%) during close contact. Accordingly, university students showed greater exposure potential in dormitories than school students in homes, however, a lower exposure was observed in classrooms and postgraduate student offices in comparison with school students in classrooms. In addition, restaurants had the highest aerosol exposure volume for both short-range inhalation and direct deposition on the facial mucosa. Thus, the classroom was established as the primary indoor environment where school students are exposed to aerosols.

Numerical investigation of impinging jet ventilation in ICUs: Is thermal stratification a problem?

Intensive care units (ICUs) are the high incidence sites of hospital-acquired infections, where impinging jet ventilation (IJV) shows great potential. Thermal stratification of IJV and its effect on contaminants distribution were systematically investigated in this study. By changing the setting of heat source or the air change rates, the main driving force of supply airflow can be transformed between thermal buoyancy and inertial force, which can be quantitatively described by the dimensionless buoyant jet length scale (lm¯). For the investigated air change rates, namely 2 ACH to 12 ACH, lm¯ varies between 0.20 and 2.80. The thermal buoyancy plays a dominant role in the movement of the horizontally exhaled airflow by the infector under low air change rate, where the temperature gradient is up to 2.45 °C/m. The flow center remains close to the breathing zone of the susceptible ahead, resulting into the highest exposure risk (6.6‰ for 10-µm particles). With higher heat flux of four PC monitors (from 0 W to 125.85 W for each monitor), the temperature gradient in ICU rises from 0.22 °C/m to 1.02 °C/m; however, the average normalized concentration of gaseous contaminants in the occupied zone is reduced from 0.81 to 0.37, because their thermal plumes are also able to carry containments around them to the ceiling-level readily. As the air change rate was increased to 8 ACH (lm¯=1.56), high momentum weakened the thermal stratification by reducing the temperature gradient to 0.37 °C/m and exhaled flow readily rose above the breathing zone; the intake fraction of susceptible patient located in front of the infector for 10-µm particles reduces to 0.8‰. This study proved the potential application of IJV in ICUs and provides theoretical guidance for its appropriate design.}.

Tracing the origin of large respiratory droplets by their deposition characteristics inside the respiratory tract during speech.

Origin of differently sized respiratory droplets is fundamental for clarifying their viral loads and the sequential transmission mechanism of SARS-CoV-2 in indoor environments. Transient talking activities characterized by low (0.2 L/s), medium (0.9 L/s), and high (1.6 L/s) airflow rates of monosyllabic and successive syllabic vocalizations were investigated by computational fluid dynamics (CFD) simulations based on a real human airway model. SST k-ω model was chosen to predict the airflow field, and the discrete phase model (DPM) was used to calculate the trajectories of droplets within the respiratory tract. The results showed that flow field in the respiratory tract during speech is characterized by a significant laryngeal jet, and bronchi, larynx, and pharynx-larynx junction were main deposition sites for droplets released from the lower respiratory tract or around the vocal cords, and among which, over 90% of droplets over 5 µm released from vocal cords deposited at the larynx and pharynx-larynx junction. Generally, droplets' deposition fraction increased with their size, and the maximum size of droplets that were able to escape into external environment decreased with the airflow rate. This threshold size for droplets released from the vocal folds was 10-20 µm, while that for droplets released from the bronchi was 5-20 µm under various airflow rates. Besides, successive syllables pronounced at low airflow rates promoted the escape of small droplets, but do not significantly affect the droplet threshold diameter. This study indicates that droplets larger than 20 µm may entirely originate from the oral cavity, where viral loads are lower; it provides a reference for evaluating the relative importance of large-droplet spray and airborne transmission route of COVID-19 and other respiratory infections.

Effects of individualized dietary counseling on nutritional status and quality of life in post-discharge patients after surgery for gastric cancer: A randomized clinical trial.

Background: Currently, the supporting evidence for dietary counseling is insufficient. The aim of this study is to evaluate the impact of individualized dietary counseling on nutritional outcomes and quality of life (QOL) in patients undergoing surgery for gastric cancer. Methods: This study was a prospective, single-center, randomized controlled trial. The patients after surgery for gastric cancer were randomly assigned (1:1) to the intervention group and the control group. In the intervention group, patients receive individualized dietary counseling based on individual calorie needs and symptom assessment at 24 h before discharge, 14, 21, 30, and 60 days postoperatively. Patients in the control group received routine dietary counseling. The primary endpoint was body mass index (BMI) loss at 30, 60, and 90 days after surgery; the secondary endpoints were calorie and protein intake at 30 and 60 days after surgery, blood parameters, the 90-day readmission rate, and QOL at 90 days after surgery. Results: One hundred thirty patients were enrolled; 67 patients were assigned to the intervention group and 63 patients to the control group. Compared with the control group, patients in the intervention group were significantly less BMI loss at 30 days (-0.84 ± 0.65 vs. -1.29 ± 0.83), 60 days (-1.29 ± 0.92 vs. -1.77 ± 1.13), and 90 days (-1.37 ± 1.05 vs. -1.92 ± 1.66) after surgery (all P< 0.05). Subgroups analysis by surgery type showed that the intervention could significantly reduce BMI loss in patients undergoing total and proximal gastrectomy at 30 days (-0.75 ± 0.47 vs. -1.55 ± 1.10), 60 days (-1.59 ± 1.02 vs. -2.55 ± 1.16), and 90 days (-1.44 ± 1.19 vs. -3.26 ± 1.46) after surgery (all P< 0.05). At 60 days after surgery, calorie goals were reached in 35 patients (77.8%) in the intervention group and 14 patients (40.0%) in the control group (P = 0.001), and protein goals were reached in 40 patients (88.9%) in the intervention group and 17 patients (48.6%) in the control group (P< 0.001). Regarding the QOL at 90 days after surgery, the patients in the intervention group had a significantly lower level of fatigue, shortness of breath and stomach pain, better physical function, and cognitive function (P< 0.05). Conclusions: Post-discharge individualized dietary counseling is an effective intervention to reduce post-gastrectomy patient weight loss and to elevate calorie intake, protein intake, and QOL.

The effect of thermodynamic changes in the cooling of saline soils on the corrosion system of carbon steels.

In this experiment, Q235 and X80 carbon steels, which are widely used in oil and gas pipelines and ancillary facilities, were selected to study the changes in the corrosion behaviour and mechanism of carbon steels in the process of natural saline soil cooling to a freezing state through electrochemical testing. The equivalent circuit model of carbon steel before and after the freezing phase transformation in the soil was determined. Based on the corrosion kinetic parameters and soil thermodynamic changes, the influencing factors of steel corrosion during the cooling process were systematically analysed. It was found that temperature mainly affected carbon steel corrosion by changing the properties of the solution. The main factors affecting the corrosion behaviour of the carbon steel were the thermal motion of molecules, ions, and electrons in solution, oxygen dissolution and diffusion, ion adsorption, diffusion mass transfer, and unfrozen water content change during the cooling process.

Indoor dryness and humidification-induced arsenic inhalation exposure above 4200 m in Ngari, China.

Ngari Prefecture, Tibet, China, features its ultrahigh altitude above 4200 m, very little annual precipitation and extremely low relative humidity. Residents who have migrated to Tibet from the plains use indoor humidification to reduce the respiratory discomfort caused by prolonged exposure to dry indoor air. In this study, field investigations and analysis of residential indoor environments and humidification methods in Ngari Prefecture revealed that ninety-eight percent of humidifier consumers in the prefecture used low-cost ultrasonic humidifiers filled with indoor tap water. The results revealed that the arsenic (As) concentration of the tap water was 41.6 µg/L, over four times China's standards for drinking water quality (10 µg/L). The source As concentration in the air humidified by the tap water-filled ultrasonic humidifier is (619.8 ± 59.1) (ng/m3 ·air), while no As was detected in the air humidified by the evaporative humidifier. For ultrasonic humidifier with tap water-filled, the inhalation dose of a healthy adult was 45.4 ng/d. The minute ventilation volume of migrated residents who had been in Ngari for less than two years (12.5 ± 4.3 L/min) was greater than those of the long-term residents (10.0 ± 4.5 L/min), which may exacerbate the short-term inhalation exposure risk for migrated residents. To reduce the health risks associated with As exposure, evaporative humidifiers are recommended for households using domestic water. If ultrasonic humidifiers are used, the tap water must be purified with terminal filters.

Close contact behavior-based COVID-19 transmission and interventions in a subway system.

During COVID-19 pandemic, analysis on virus exposure and intervention efficiency in public transports based on real passenger's close contact behaviors is critical to curb infectious disease transmission. A monitoring device was developed to gather a total of 145,821 close contact data in subways based on semi-supervision learning. A virus transmission model considering both short- and long-range inhalation and deposition was established to calculate the virus exposure. During rush-hour, short-range inhalation exposure is 3.2 times higher than deposition exposure and 7.5 times higher than long-range inhalation exposure of all passengers in the subway. The close contact rate was 56.1 % and the average interpersonal distance was 0.8 m. Face-to-back was the main pattern during close contact. Comparing with random distribution, if all passengers stand facing in the same direction, personal virus exposure through inhalation (deposition) can be reduced by 74.1 % (98.5 %). If the talk rate was decreased from 20 % to 5 %, the inhalation (deposition) exposure can be reduced by 69.3 % (73.8 %). In addition, we found that virus exposure could be reduced by 82.0 % if all passengers wear surgical masks. This study provides scientific support for COVID-19 prevention and control in subways based on real human close contact behaviors.

Exposure and respiratory infection risk via the short-range airborne route.

Leading health authorities have suggested short-range airborne transmission as a major route of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). However, there is no simple method to assess the short-range airborne infection risk or identify its governing parameters. We proposed a short-range airborne infection risk assessment model based on the continuum model and two-stage jet model. The effects of ventilation, physical distance and activity intensity on the short-range airborne exposure were studied systematically. The results suggested that increasing physical distance and ventilation reduced short-range airborne exposure and infection risk. However, a diminishing return phenomenon was observed when the ventilation rate or physical distance was beyond a certain threshold. When the infectious quantum concentration was less than 1 quantum/L at the mouth, our newly defined threshold distance and threshold ventilation rate were independent of quantum concentration. We estimated threshold distances of 0.59, 1.1, 1.7 and 2.6 m for sedentary/passive, light, moderate and intense activities, respectively. At these distances, the threshold ventilation was estimated to be 8, 20, 43, and 83 L/s per person, respectively. The findings show that both physical distancing and adequate ventilation are essential for minimising infection risk, especially in high-intensity activity or densely populated spaces.

Electrochemical Corrosion Behaviour of X70 Steel under the Action of Capillary Water in Saline Soils.

In this paper, the electrochemical corrosion behavior of X70 steel in saline soil under capillary water was simulated by a Geo-experts one-dimensional soil column instrument. A volumetric water content sensor and conductivity test were used to study the migration mechanism of water and salt (sodium chloride) under the capillary water. The electrochemical corrosion behavior of the X70 steel in the corrosion system was analyzed by electrochemical testing as well as the macroscopic and microscopic corrosion morphology of the steel. The test results showed that the corrosion behavior of X70 steel was significantly influenced by the rise of capillary water. In particular, the wetting front during the capillary water rise meant that the X70 steel was located at the three-phase solid/liquid/gas interface at a certain location, which worsened its corrosion behavior. In addition, after the capillary water was stabilized, the salts were transported with the capillary water to the top of the soil column. This resulted in the highest salt content in the soil environment and the most severe corrosion of the X70 steel at this location.

Study on short-term cosmetic effects and quality of life after breast cancer modified radical mastectomy combined with one-stage prosthesis implantation.

Background: This study investigated the reconstruction effect of skin-preserving breast cancer modified radical mastectomy combined with one-stage breast prosthesis implantation in female patients to analyze relevant factors and observe the effect of prosthesis reconstruction on short-term breast satisfaction, psycho-social functions, and quality of life (QOL) in patients with breast cancer after the operation. Methods: Patients were divided into two groups based on the reconstruction effect (an excellent effect group and a good and general effect group). Patients' short-term cosmetic effect on the breast after breast cancer modified radical mastectomy combined with one-stage breast prosthesis implantation was prospectively followed up to analyze influencing factors. At post-operative 6 months, the breast satisfaction dimension, psycho-social dimension, upper limb breast health dimension, and surgical satisfaction dimension in the prosthesis reconstruction module in the BREAST-Q scale were used for follow-up evaluation. Results: The excellent rate of prosthesis reconstruction was 91.3%. A significant correlation was observed among the reconstruction effect, implant volume, and number of children born by the patient (P < 0.05). The correlation with age, BMI (body mass index), operation time, nipple and areola retention, operation method, and incision was not statistically significant (P > 0.05). At post-operative 6 months, the Breast-Q score was significantly different in the overall breast satisfaction dimension and outcome satisfaction dimension between the two groups (P < 0.05). Conclusion: Breast cancer modified radical mastectomy combined with one-stage breast prosthesis implantation can not only fulfill patients' physical aesthetic needs but also positively affect their psychosocial behavior to improve post-operative QOL.

Novel strategy for membrane biofouling control in MBR with nano-MnO2 modified PVDF membrane by in-situ ozonation.

In this study, ozonation catalyst nano-MnO2 blended polyvinylidene fluoride (PVDF) membrane was fabricated via phase inversion method and applied to membrane bioreactors (MBR), and then coupled with in-situ ozonation to study the anti-biofouling performance and reveal its mechanism. Results showed that, compared with pristine PVDF membrane (MBR_M0), 0.75 wt% and 1.00 wt% nano-MnO2 modified PVDF membrane (MBR_M0.75 and MBR_M1.00) could mitigate the membrane biofouling rate. Meanwhile MBR_M1.00 coupled with in-situ ozonation could increase the membrane cleaning cycle to 1.5 and 2.7 times, compared with MBR_M0 and MBR_M0.75 without in-situ ozonation. The possible mechanisms included that the nano-MnO2 modification coupled with in-situ ozonation directly removed the biofouling on the membrane surface, improved the hydrophilicity of the membrane surface and enhanced the chemical oxidation and biodegradation of membrane biofouling contaminants in the sludge mixture. The results of this work provide a new strategy for the control of membrane biofouling in MBR to treat industrial wastewater.

Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant.

Although airborne transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been recognized, the condition of ventilation for its occurrence is still being debated. We analyzed a coronavirus disease 2019 (COVID-19) outbreak involving three families in a restaurant in Guangzhou, China, assessed the possibility of airborne transmission, and characterized the associated environmental conditions. We collected epidemiological data, obtained a full video recording and seating records from the restaurant, and measured the dispersion of a warm tracer gas as a surrogate for exhaled droplets from the index case. Computer simulations were performed to simulate the spread of fine exhaled droplets. We compared the in-room location of subsequently infected cases and spread of the simulated virus-laden aerosol tracer. The ventilation rate was measured using the tracer gas concentration decay method. This outbreak involved ten infected persons in three families (A, B, C). All ten persons ate lunch at three neighboring tables at the same restaurant on January 24, 2020. None of the restaurant staff or the 68 patrons at the other 15 tables became infected. During this occasion, the measured ventilation rate was 0.9 L/s per person. No close contact or fomite contact was identified, aside from back-to-back sitting in some cases. Analysis of the airflow dynamics indicates that the infection distribution is consistent with a spread pattern representative of long-range transmission of exhaled virus-laden aerosols. Airborne transmission of the SARS-CoV-2 virus is possible in crowded space with a ventilation rate of 1 L/s per person.

New insight into increased toxicity during ozonation of chlorophenol: The significant contribution of oxidizing intermediates.

Biological safety evaluation and toxic by-products identification are critical issues in the partial oxidation process. Previous studies have shown that the whole toxicity increased in the effluent of an ozonation process for chlorophenols removal. Here, this study systematically investigated the changes of acute toxicity during the ozonation of 3-chlorophenol under four key operational conditions, including initial 3-chlorophenol concentration (20-60 mg/L), ozone concentration (14-42 mg/L), reaction pH (3-10) and ozonation time (0-50 min). The results found that the ozonation process induced a significant increase in the acute toxicity, followed by its gradual decrease. The observation of higher acute toxicity increase generally happened at higher initial 3-chlorophenol concentration, lower ozone concentration and lower reaction pH. At the toxicity peaks, the oxidizing intermediates posed acute toxicity equal to 65.8%-96.3% of the whole toxicity. Among them, free active chlorine (FAC) contributed 21.4%-51.6%, and its concentrations significantly correlated to the acute toxicity change. Therefore, two possible FAC generation pathways initiated by ozone molecule were proposed: (i) bond breaking of the oxychloride complex formed by the combination of chloride ion and zwitterion; or (ii) hydrolysis of ozonides formed by the electrophilic reaction of ozone molecule. Together, these results firstly revealed the significant toxicity contribution of oxidizing intermediates during the ozonation of chlorophenols, supporting further development of safe and effective ozone-based water treatment schemes.

Multi-route respiratory infection: When a transmission route may dominate.

The exact transmission route of many respiratory infectious diseases remains a subject for debate to date. The relative contribution ratio of each transmission route is largely undetermined, which is affected by environmental conditions, human behaviour, the host and the microorganism. In this study, a detailed mathematical model is developed to investigate the relative contributions of different transmission routes to a multi-route transmitted respiratory infection. The following transmission routes are considered: long-range airborne transmission, short-range airborne transmission, direction inhalation of medium droplets or droplet nuclei, direct deposition of droplets of all sizes, direct and indirect contact route. It is illustrated that all transmission routes can dominate the total transmission risk under different scenarios. Influential parameters considered include the dose-response rate of different routes, droplet governing size that determines pathogen content in droplets, exposure distance, and pathogen dose transported to the hand of infector. Our multi-route transmission model provided a comprehensive but straightforward method to evaluate the probability of respiratory diseases transmission via different routes. It also established a basis for predicting the impact of individual-level intervention methods such as increasing close-contact distance and wearing protective masks.

Multi-route transmission potential of SARS-CoV-2 in healthcare facilities.

Understanding the transmission mechanism of SARS-CoV-2 is a prerequisite to effective control measures. To investigate the potential modes of SARS-CoV-2 transmission, 21 COVID-19 patients from 12-47 days after symptom onset were recruited. We monitored the release of SARS-CoV-2 from the patients' exhaled breath and systematically investigated environmental contamination of air, public surfaces, personal necessities, and the drainage system. SARS-CoV-2 RNA was detected in 0 of 9 exhaled breath samples, 2 of 8 exhaled breath condensate samples, 1 of 12 bedside air samples, 4 of 132 samples from private surfaces, 0 of 70 samples from frequently touched public surfaces in isolation rooms, and 7 of 23 feces-related air/surface/water samples. The maximum viral RNA concentrations were 1857 copies/m3 in the air, 38 copies/cm2 in sampled surfaces and 3092 copies/mL in sewage/wastewater samples. Our results suggest that nosocomial transmission of SARS-CoV-2 can occur via multiple routes. However, the low detection frequency and limited quantity of viral RNA from the breath and environmental specimens may be related to the reduced viral load of the COVID-19 patients on later days after symptom onset. These findings suggest that the transmission dynamics of SARS-CoV-2 differ from those of SARS-CoV in healthcare settings.

Probable Evidence of Fecal Aerosol Transmission of SARS-CoV-2 in a High-Rise Building.

BACKGROUND: The role of fecal aerosols in the transmission of severe acute respiratory syndrome coronavirus 2 has been suspected. OBJECTIVE: To investigate the temporal and spatial distributions of 3 infected families in a high-rise apartment building and examine the associated environmental variables to verify the role of fecal aerosols. DESIGN: Epidemiologic survey and quantitative reverse transcriptase polymerase chain reaction analyses on throat swabs from the participants; 237 surface and air samples from 11 of the 83 flats in the building, public areas, and building drainage systems; and tracer gas released into bathrooms as a surrogate for virus-laden aerosols in the drainage system. SETTING: A high-rise apartment building in Guangzhou, China. PARTICIPANTS: 9 infected patients, 193 other residents of the building, and 24 members of the building's management staff. MEASUREMENTS: Locations of infected flats and positive environmental samples, and spread of virus-laden aerosols. RESULTS: 9 infected patients in 3 families were identified. The first family had a history of travel to the coronavirus disease 2019 (COVID-19) epicenter Wuhan, whereas the other 2 families had no travel history and a later onset of symptoms. No evidence was found for transmission via the elevator or elsewhere. The families lived in 3 vertically aligned flats connected by drainage pipes in the master bathrooms. Both the observed infections and the locations of positive environmental samples are consistent with the vertical spread of virus-laden aerosols via these stacks and vents. LIMITATION: Inability to determine whether the water seals were dried out in the flats of the infected families. CONCLUSION: On the basis of circumstantial evidence, fecal aerosol transmission may have caused the community outbreak of COVID-19 in this high-rise building. PRIMARY FUNDING SOURCE: Key-Area Research and Development Program of Guangdong Province and the Research Grants Council of Hong Kong.