Floor Drain Research Articles

Rethinking residential building design in high-density cities for enhancing pandemic resilience: Balancing importance and practicality

The relationship between the built environment and epidemic transmission is particularly pronounced within the context of lockdown policies and high-density urban areas. Non-pharmaceutical interventions have become increasingly important during and after the COVID-19 pandemic. This study proposes an evaluation index system for pandemic-resilient residential building designs in high-density cities, covering the entire design process including site planning, architecture design, building equipment and management. The system includes 64 design strategies, categorized into 15 sub-categories and 4 categories. Then, we evaluate the preference of each strategy by synthesizing the dimensions of importance and implementation difficulty. A questionnaire survey was conducted among experts who have experience with pandemic-resilient designs in high-density cities. Fuzzy synthetic evaluation analysis was implemented along with the “preference index” concept to identify the most important and practical interventions during the pandemic outbreak. The results indicate that “service and management” is the category that requires priority, followed by “property management,” “common areas” and “building morphology” in sub-categories. Among the design strategies, “waste receptacle,” “publicity and education,” “floor drain and water seal” and “environmental cleaning and disinfection” are the top four recommended strategies. This study provides policymakers and practitioners with effective and easily implementable prevention measures during an outbreak of respiratory tract infections. It also offers specific policy recommendations and application suggestions for new and existing buildings, contributing to creating a safer and healthier living environment.

Vertical transmission of infectious aerosols through building toilet drainage system: An experimental study

The building's toilet drainage system has been identified as a potential route for the transmission of SARS-CoV-2 during outbreaks. This study employed agar-fluorescein sodium semi-solid as trace particles to investigate the possibility of vertical transmission of the SARS-CoV-2 in drainage system. In both scenarios, where floor drains were all properly sealed or dried out, simulated faeces containing fluorescein sodium were flushed into the toilet bowl. Air sampling was conducted in each restroom, and differential pressure measurements at the floor drain locations were taken. The experimental results showed that when all floor drains were properly sealed, the differential pressure at each floor drain was 0. The fluorescein sodium-traced aerosol did not transmit through the drainage system to various floors, which significantly reduced the risk of infection for users through this route. However, when all floor drains dried out, toilet users above the neutral pressure layer (NPL) were at a high risk of virus infection. Due to the increasing maximum negative pressure at the floor drain above the NPL with ascending floor levels, users on each floor above the NPL faced an elevated infection risk in restrooms. Specifically, users on the top floor were exposed to infectious aerosols roughly 1.6 times that of the first floor above the NPL. Conversely, owing to the increasing maximum positive pressure at the floor drain below the NPL with descending floor levels, users below the NPL experienced a comparatively lower infection risk. This finding has important implications for understanding the vertical transmission dynamics of SARS-CoV-2 in residential or public building and can inform the development of effective control measures.

A novel method using a differential staining fluorescence microscopy (DSFM) to track the location of enteric pathogens within mixed-species biofilms

This study developed a new tool, differential staining fluorescence microscopy (DSFM), to measure the biovolume and track the location of enteric pathogens in mixed-species biofilms which can pose a risk to food safety in beef processing facilities. DSFM was employed to examine the impact of pathogenic bacteria, Escherichia coli O157:H7 and three different Salmonella enterica strains on mixed-species biofilms of beef processing facilities. Fourteen floor drain biofilm samples from three beef processing plants were incubated with overnight BacLight stained enteric pathogens at 7 °C for 5 days on stainless steel surface then counter-stained with FM-1-43 biofilm stain and analyzed using fluorescence microscopy. Notable variations in biovolume of biofilms were observed across the fourteen samples. The introduction of E. coli O157:H7 and S. enterica strains resulted in diverse alterations of biofilm biovolume, suggesting distinct impacts on mixed-species biofilms by different enteric pathogens which were revealed to be located in the upper layer of the mixed-species biofilms. Pathogen strain growth curve comparisons and verification of BacLight Red Stain staining effectiveness were validated. The findings of this study show that the DSFM method is a promising approach to studying the location of enteric pathogens within mixed-species biofilms recovered from processing facilities. Understanding how foodborne pathogens interact with biofilms will allow for improved targeted antimicrobial interventions.

Evaluation of vacuum packaging for extending the shelf life of Sardinian fermented sausage

Salsiccia sarda or Sardinian fermented sausage is a traditional dry-fermented sausage included in the list of traditional food products of Sardinia (Italy). At the request of some producing plants, the possibility of extending the shelf life of the vacuum-packed product up to 120 days was evaluated. Manufacturing of 90 samples, representing 3 different batches of Sardinian fermented sausage was carried out in two producing plants (A and B). In the packaged product and subsequently every 30 days for four months (T0, T30, T60, T120), the following analyses were conducted on all samples: physicochemical characteristics, total aerobic mesophilic count, Enterobacteriaceae count, detection of Listeria monocytogenes, Salmonella spp., mesophilic lactic acid bacteria, and coagulase-positive Staphylococci. Moreover, surfaces in contact and surfaces not in contact with food were sampled in both producing plants. Sensory profile analysis was also performed for every analysis time. At the end of the extended shelf life, pH values were equal to 5.90±0.11 (producing plant A) and 5.61±0.29 (producing plant B). Water activity mean values at T120 were 0.894±0.02 (producing plant A) and 0.875±0.01 (producing plant B). L. monocytogenes was detected in 73.3% (33/45) of the samples from producing plant A, with mean levels of 1.12±0.76 log10 CFU/g. In producing plant B, L. monocytogenes was never detected. Enterobacteriaceae were detected in 91.1% (41/45) of samples in producing plant A with mean values of 3.15±1.21 log10 CFU/g, and in 35.5% (16/45) samples in producing plant B samples with mean values of 0.72±0.86 log10 CFU/g. Salmonella and Staphylococcus aureus were never detected. Regarding environmental samples, the sites that were most contaminated by L. monocytogenes were the bagging table (contact surface) and processing room floor drains (non-contact surface) with a prevalence of 50% each (8/16 positive samples for both sampling sites). Sensory analysis results showed that at T30 the overall sensory quality was at its highest; moreover, the visual-tactile aspect, the olfactory characteristics, the gustatory aspects, and the texture showed significant differences in samples throughout the shelf life, with a decreased intensity at 120 days of storage. Overall, the quality and sensory acceptance of the vacuum-packed Sardinian fermented sausage were not affected until 120 days of shelf-life. However, the possible contamination by L. monocytogenes calls attention to the hygienic management of the entire technological process. The environmental sampling was confirmed as a useful verification tool during control.

Financial comparison of sewage treatment and disposal systems in rural areas

Studies show that conventional sanitation technologies, due to their high costs, end up excluding rural populations. Among the options for the treatment and final disposal of sewage in rural areas we can mention septic tanks with sump and biodigester tanks with filtering gardens. In view of the above, the objective of this article is to make a financial comparison of two individual sewage treatment systems: septic tank with floor drain, and biodigester septic tank with filtering garden. To perform the financial analysis in the case of the septic tank with drain, the amounts were calculated based on the dimensions indicated by ASPROESTE (2018). For the biodigester septic tank with filtering garden, the quantities of materials indicated by ASPROESTE (2018) were adopted for the case of a residence with 5 people. Finally, after the quantities raised, taking as a basis the prices contained in the National Research System of Costs and Indexes of Civil Construction (SINAPI) the costs of implementation of these devices were estimated. The results show that the septic tank system with drain presented a cost of R$ 2580.22 and the biodigester tank system a total cost of R$ 8,682.93. It is concluded that the biodigester septic tank system is more expensive, but allows the reuse of the effluent as biofertilizer, and the values found are relatively high for low-income populations, being indicated the creation of government programs, which deliver these devices for the poorest population.

INTEGRAL METHODS FOR CONTROL OF COMPLEX PROCESSES IN NPP COOLING SYSTEMS

The relevance of the study is to ensure the reliable operation of NPP recirculating cooling water systems (RCWS) and select the method for discharge water conditioning. The purpose of the study is to provide scientific and technical substantiation of conditions that will effectively provide and improve the reliable and efficient long-term operation of NPP RCWS equipment. The study included analysis of main factors that influence the efficient and reliable performance of heat exchangers, and of modern scientific and technical approaches to study water-chemical regimes (WCR) of operating RCWS systems for preventing depositions of sparingly soluble salts and corrosion of power equipment, to study thermal-hydraulic regimes (THR) in RCWS WCR laboratory simulation, and to study the deposition rates on heat exchange surfaces (HES). The improvements refer to gas chromatography technique to control the content of oil product in water; the process flow diagram for the floor drain radioactive water treatment; methods of discrete control over RCWS operational efficiency with monitoring THR and WCR indicators, and deposition rates during laboratory studies and industrial tests. The obtained results make it possible to carry out a scientific and technical substantiation of the conditions for effective implementation of RCWS structural reconfigurations in order to increase the installed capacity factor (ICF) and for economical use of water during the variable loads on individual power units of large power facilities, considering their installed capacity, service life, and heat exchange equipment condition due to the use of separate RCWS with individual THR, WCR, and established individual standards for the amount of blowdown water and its possible reuse as makeup water for power units.

Nanodispersion of ferrocianides for purification of man-made contaminated water containing caesium

A method of obtaining a nanodispersion of nickel-potassium ferrocyanides intended for purification of man-made polluted waters is proposed. It is applicable to purify effluent and floor drain water at nuclear power plants, which contains caesium, strontium, cobalt, manganese and other transition metals. The optimal conditions for the synthesis of nanodispersion have been determined, which is represented by clusters of nanoparticles associated with water molecules and nitrates dispersed in a dilute solution of nickel and potassium nitrates. On the surface of the formed nanocrystals there are fragments of structures of smaller formations. The mechanism of sorption of ions of alkali, alkaline earth and transition metals is investigated considering the ion charge density. The effect of competing ions (strontium, cobalt, manganese) on the sorption of caesium is taken into account. An integrated method of purification of multi-component man-made solutions including drainage waters of nuclear power plants is based on the use of nanodispersion of nickel-potassium ferrocyanides in combination with bentonite clay, which allows removing caesium from the drainage simulator with an efficiency of 96%, and strontium and transition metal ions (cobalt, manganese, copper, iron) with an efficiency of at least 98%.

Research on the relationship between architectural features in northeast China and vertical aerosol transmission of COVID-19.

During the COVID-19 pandemic, many buildings in northeast China have had clusters of infected cases in the vertical layout. There is speculation that vertical aerosol transmission occurs. The houses in northeast China are airtight, and range hoods may be used for a long period of time when cooking. The pathway and factors influencing vertical aerosol transmission are worth studying. To elucidate a viral aerosol transmission pathway, we selected a multistory apartment and a high-rise building in Changchun city, Jilin province, China, to conduct an in-depth investigation and on-site simulation experiments. According to epidemiological investigation information on infected cases, building structures, drainage, ventilation, etc., we used fluorescent microspheres to simulate the behaviors of infected people, such as breathing and flushing the toilet after defecation, to discharge simulated viruses and track and monitor them. The field simulation experiment confirmed the transmission of fluorescent microsphere aerosols to other rooms in two types of buildings using a vertical aerosol transmission pathway of toilet flush-sewage pipe-floor drain without a water seal. Our study showed that, in the absence of a U-shaped trap or floor drain water seal whether in a multistory apartment or high-rise residential building, there is a transmission pathway of "excretion of virus through feces-toilet flushing-sewage pipe-floor drain without water seal," which will cause the vertical transmission of viral aerosol across floors during the COVID-19 pandemic. Moreover, the negative pressure generated by turning on the range hood when closing doors and windows increase aerosol transmission. Based on this negative pressure, prevention and control measures for residential buildings in northeast China during the COVID-19 pandemic were proposed.

Neglected Aspects of SARS-CoV-2 Aerosol Transmission in Bathrooms of Multistory and High-Rise Buildings - Beijing Municipality, China, October 2022.

There is a toilet flush-soil stack-floor drain pathway of aerosol transmission in multistory and high-rise buildings, but the influencing factors are not completely clear. The poor airtightness of the connecting parts of the floor drain, as well as pressure fluctuations in the sewage pipe during toilet flushing caused by blockage of the soil stack vent, may lead to the cross-floor transmission of viral aerosols through the soil stack and floor drains. In multistory and high-rise buildings, the bathroom floor drains should be kept sealed, and floor drain connecting parts should be airtight. Furthermore, the soil stack vent should not be blocked. In this way, the cross-floor transmission of viral aerosols can be effectively reduced.

Probable Evidence of Aerosol Transmission of SARS-COV-2 in a COVID-19 Outbreak of a High-Rise Building.

Although it is well established that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can be transmitted through aerosols, the mode of long-range aerosol transmission in high-rise buildings remains unclear. In this study, we analyzed an outbreak of coronavirus disease 2019 (COVID-19) that occurred in a high-rise building in China. Our objective was to investigate the plausibility of aerosol transmission of SARS-CoV-2 by testing relevant environmental variables and measuring the dispersion of a tracer gas in the drainage system of the building. The outbreak involved 7 infected families, of which 6 were from vertically aligned flats on different floors. Environmenìtal data revealed that 3 families' bathrooms were contaminated by SARS-CoV-2. In our tracer experiment, we injected tracer gas (CO2) into the dry floor drains and into water-filled toilets in the index case' s bathroom. Our findings showed that the gas could travel through vertical pipes by the dry floor drains, but not through the water of the toilets. This indicates that dry floor drains might facilitate the transmission of viral aerosols through the sewage system. On the basis of circumstantial evidence, long-range aerosol transmission may have contributed to the community outbreak of COVID-19 in this high-rise building. The vertical transmission of diseases through aerosols in high-rise buildings demands urgent attention.

Characterization of Salmonella Strains and Environmental Microorganisms Isolated From a Meat Plant With Salmonella Recurrence

Salmonella entericais a leading cause of foodborne illness in the United States. In this study, 3S. enterica strains (serovars Cerro, Montevideo, and Typhimurium) were isolated from a beef processing plant with a history of Salmonella recurrence. Floor drains of the hotbox area and storage cooler of the same plant were sampled for environmental microorganisms. Biofilm formation on stainless steel (SS) by the microorganisms recovered from the drains and surface colonization by the isolated S. enterica strains were assessed. Pathogen survival and community compositions after sanitization (quaternary ammonium compound [QAC]) were examined. Alone the Cerro strain exhibited greater (P<0.05) surface attachment (5.4 log10CFU/SS chip) than the Montevideo or Typhimurium strains (4.6 and 4.8 log10CFU/SS chip, respectively). The Typhimurium strain was the most QAC tolerant (0.3 log reduction), whereas the Cerro and Montevideo strains exhibited similar sensitivities (1.6 log and 1.1 log reduction, respectively). The environmental microorganisms from the drain samples all developed biofilms ranging from 5.7 to 6.0 log10CFU/SS chip. All S. enterica strains were efficiently integrated into the drain biofilms where the Montevideo and Typhimurium strains ranged from 3.8 to 4.7 log10CFU/chip and the Cerro strain 4.0 to 5.8 log10CFU/chip. Enhanced QAC tolerance was only exhibited by the Montevideo strain when integrated into the drain biofilms. Metagenomic analysis of the drain biofilms showed that the most abundant genus was Pseudomonas (57.7%), followed by Brochothrix (28.6%), Serratia (7.2%), Lactococcus (4.2%), and Carnobacterium (1.1%), with all varying significantly among the different biofilm samples and their response to QAC treatment. Thus,various factors underlie the survival advantages of the S. enterica strains, allowing them to tolerate stress as well as out-compete and coexist with environmental companion bacteria for protection, which might lead to pathogen prevalence and recurrent product contamination.

Hygiene Indicators and Salmonellae on Surfaces of Swine Carcasses from Two Slaughterhouses in Northern Portugal

The monitoring of carcass surface contamination along the slaughter line enables verification of slaughter operation hygiene and the use of good manufacturing practices. Pork meat is a common source of human nontyphoidal salmonellosis, one of the most frequently reported foodborne illnesses worldwide. This study was conducted to gather data on microbial loads before and after evisceration on the surfaces of swine carcasses in two slaughterhouses. The presence of Salmonella enterica was evaluated only after evisceration on carcass surfaces and in livers and floor drains (environmental samples) because pigs are common carriers of this pathogen. The contamination of carcass surfaces was evaluated by delimitation of surface area with sterilized templates (100 cm2), and surface samples were collected with gauze swabs. Total aerobic mesophilic bacteria, Enterobacteriaceae, and Escherichia coli were enumerated. Significant differences (P < 0.05) in counts of mesophilic bacteria, Enterobacteriaceae, and E. coli were found on the external carcass surfaces, with higher counts after evisceration. The neck and abdominal areas had higher levels of mesophilic bacteria, Enterobacteriaceae, and E. coli and a high prevalence of Salmonella. Salmonella was detected in only one of the studied slaughterhouses; 19 (7.3%) of 259 analyzed carcass samples were positive for Salmonella, and Salmonella was detected in two livers and two floor drains. A total of 52 Salmonella isolates (44 from carcasses, 5 from livers, and 3 from drains) were recovered. Three Salmonella serovars (Typhimurium 4,5:i- , Wernigerone, and Derby) were identified, and 53.8% of the 52 isolates were multidrug resistant. The results reveal the need for continuous improvement of slaughtering operations and implementation of good manufacturing practices to ensure the safety of pork produced in Portugal.

Efficacy of Selected Powdered Floor Treatments against Salmonella, Escherichia coli, and Listeria Monocytogenes on Polyurethane-Concrete Flooring Material Carriers

Food processing environment flooring can become contaminated with pathogens in many ways including foot and equipment traffic, incoming materials, and floor drain backups. Natural antimicrobial turmeric and commercially available powdered floor treatments may reduce the levels of pathogens on flooring thereby reducing the risk of cross contamination from the floor to food contact surfaces. These chemicals were evaluated to determine their effectiveness against cocktails of Salmonella , Escherichia coli , and Listeria monocytogenes dried onto the surfaces of carriers made from polyurethane-concrete commercial flooring material. Aqueous test solutions were prepared from the minimum treatment required per m 2 from the manufacturer's instructions diluted in sterile water. Potential synergy between turmeric and a percarbonate based commercial floor treatment was explored with a mixture of turmeric and sodium percarbonate, each at approximately 37g/m 2 application rate. Each inoculated carrier was exposed to the treatment solutions or a sterile water control for 10 minutes at room temperature, neutralized with Hi-Cap neutralizing broth, the bacteria suspended, enumerated, and log 10 reductions calculated for each treatment and inoculum combination. Mean log 10 CFU/carrier reductions with standard deviations ranged between 4.29±0.34 for the sodium percarbonate (SPC) based treatment and 0.004±0.23 for turmeric for Salmonella , 4.81±0.16 for SPC based treatment and -0.16±0.62 for turmeric for E. coli , and 4.88±0.6 for SPC based treatment and -0.16±0.15 for turmeric for L. monocytogenes .

A Targeted Needs Assessment for the Development of a Surgical Sub-internship Curriculum

Medical students often feel inadequately prepared for the responsibilities of surgical internship because of insufficient exposure to resident responsibilities prior to starting residency. This lack of preparation may contribute to burnout and attrition early in residency. Sub-internships should provide these experiences. Significant variation, however, exists in the structure of these rotations. We conducted a targeted needs assessment to inform the development of a didactic curriculum to address gaps in the surgical sub-internship experience and better prepare students for general surgery residency. A 25-item needs assessment survey was developed and distributed to senior medical students in their surgical sub-internship, current junior residents, and prior students (alumni) from the past 4 years who matched into general surgery residencies at other institutions. Geisel School of Medicine at Dartmouth/Dartmouth-Hitchcock Medical Center, a tertiary-care academic medical center. Nine senior medical students; 12 current residents and 14 alumni, including 9 PGY-1, 13 PGY-2, and 4 PGY-3 residents. The topics rated most important by medical students were floor management topics, specifically lines, tubes, and drains, hypotension, post-operative fever, chest pain, oliguria, and post-operative pain. In contrast, there was a wider variety of topics rated highly by residents. Residents emphasized non-technical communication and documentation skills. Residents at every training level rated presenting patients on rounds as the most important skill for incoming interns to acquire, whereas only one-third of medical students considered this to be an essential topic. Medical students rank management of common clinical problems as the most critical aspect in their preparation for residency. Residents recognized these topics as important, but also placed high emphasis on non-technical communication and documentation skills. The findings from this need's assessment can be used to guide content structure for a sub-intern curriculum.

Numerical investigation on the transmission and dispersion of aerosols in a 7-stories building drainage system

In previous reports, the positive SARS-CoV-2 nucleic acid was detected in the fecal samples from confirmed pneumonia patients, suggesting a high probability of the fecal-oral transmission. To date, however, the role played by the drainage system of a high-rise building in the virus transmission is not clear and especially studies on the dynamics mechanism behind is scarce. From this point of view, the present work carries out a computational fluid dynamics (CFD) modeling to investigate the effects of the water seal effectiveness of the floor drain, the negative/positive pressures (P1, P2) in the bathroom, temperature differential (ΔT), outside wind velocity (v), the piping fittings and the negative pressure at the cowl (P3) on the transmission of the virus-laden aerosol particles in a drainage system of a typical 7-storeys residential building. The CFD models are first validated by the previous experiments in literature. Numerical results imply that the drainage system might play an essential role to the virus transmission. Then, results indicate that, the leakage risk of the aerosol particles via the floor drain with inefficient water-seal (UFD) mainly exists at the upper floors above the neutral pressure level (NPL). Besides, the negative and positive pressures at the bathroom can enhance and reduce the exposure risk of aerosol particles from the corresponding UFD, respectively. The ΔT increasing does not modify the location of the NPL. Moreover, the exposure risk of aerosol particles can be effectively avoided by the well water-sealed floor drains and/or the presence of a proper negative pressure at the cowl on the top floor. Finally, based on the CFD results, several protection suggestions on the drainage system and human activities are provided.

Numerical investigation on the influence of natural make-up air in Chinese-style residential kitchen on indoor environment in a partitioned household

In domestic kitchen, cooking leads to heat generation and particle diffusion. Due to heterogeneous air mixing in partitioned spaces, difference of indoor environment between kitchen and adjacent room exits. However, study on indoor environment in adjacent room caused by cooking is not enough. Natural make-up air from exterior window openings or cracks are still the current widely used in Chinese-style residential kitchens (CRK). This study aims to predict airflow and particle distribution in a partitioned indoor environment with a CRK. Natural make-up air from exterior kitchen window, including disorganized, air infiltration and organized airflow were defined. Computational fluid dynamics method was applied to investigate velocity, air temperature, particle concentration and airflow in adjacent room. Results show that overall indoor velocity magnitude under insufficient make-up air from exterior window was two times than that under enough make-up air. Velocity magnitude in vertical and horizontal direction was quite different, but there was little difference in different position in breathing zone. Temperature difference in adjacent room ranged from 0.5 to 2.2 °C. Up to 31.8 °C was observed in disorganized make-up air in summer condition, which could lead to thermal discomfort. PM2.5 mass concentration in adjacent room could be largely reduced by organized make-up air from kitchen window. Under air volume of 810 m3/h in the model, simulated PM2.5 mass concentration in indoor environment was the lowest. With appropriate organized make-up air volume, concentration could be largely reduced. But excessive make-up air could lead to more particle diffusion from kitchen to adjacent room. Furthermore, airflow from living room to kitchen indicated a possible transmission of contaminated pollutant from dry floor drain to the living environment.

Duration of SARS-CoV-2 positive in quarantine room environments: A perspective analysis

ObjectiveTo determine the duration of SARS-CoV-2 persistence in quarantine hotel environments. Methods39 Patients confirmed by RT-PCR were included. We collected clinical features, laboratory test results, smear sample information, and quarantine room information. Genome sequencing and phylogenetic analysis were conducted. We analyzed the factors associated with environmental contamination. ResultAmong 39 COVID-19 cases, 10 were asymptomatic and 37 were imported from aboard. We collected 271 swab samples from environmental surfaces related to observational patients. Eighteen swab samples from seven patients were positive. The highest contamination rates occurred on cups (100%), followed by hand sink (12.82%), toilet seat and flush (7.89%), telephone (5.56%), bedside table (5.56%), and floor drain (5.41%). The results showed that environmental surface contamination was associated with the clinical cycle threshold values for patients (P = 0.01) and the sampling interval time after the cases left their rooms (P = 0.03). The duration of environmental surface contamination was associated with the wet status of the sampling site (P = 0.01). ConclusionOur findings showed that environmental contamination might be attributed to the viral load in the respiratory tracts of patients and the sampling interval time after the cases left their rooms. Moist surfaces were more vulnerable to remaining SARS-CoV-2 RNA-positive. Our study highlights the importance of implementing strict chemical disinfection strategies in quarantine rooms.

Quantifying the risk of indoor drainage system in multi-unit apartment building as a transmission route of SARS-CoV-2

The COVID-19 pandemic has had a profound impact on human society. The isolation of SARS-CoV-2 from patients' feces on human cell line raised concerns of possible transmission through human feces including exposure to aerosols generated by toilet flushing and through the indoor drainage system. Currently, routes of transmission, other than the close contact droplet transmission, are still not well understood. A quantitative microbial risk assessment was conducted to estimate the health risks associated with two aerosol exposure scenarios: 1) toilet flushing, and 2) faulty connection of a floor drain with the building's main sewer pipe. SARS-CoV-2 data were collected from the emerging literature. The infectivity of the virus in feces was estimated based on a range of assumption between viral genome equivalence and infectious unit. The human exposure dose was calculated using Monte Carlo simulation of viral concentrations in aerosols under each scenario and human breathing rates. The probability of COVID-19 illness was generated using the dose-response model for SARS-CoV-1, a close relative of SARS-CoV-2, that was responsible for the SARS outbreak in 2003. The results indicate the median risks of developing COVID-19 for a single day exposure is 1.11 × 10−10 and 3.52 × 10−11 for toilet flushing and faulty drain scenario, respectively. The worst case scenario predicted the high end of COVID-19 risk for the toilet flushing scenario was 5.78 × 10−4 (at 95th percentile). The infectious viral loads in human feces are the most sensitive input parameter and contribute significantly to model uncertainty.

Impact of mixed biofilm formation with environmental microorganisms on E. coli O157:H7 survival against sanitization

Biofilm formation by foodborne pathogens is a serious threat to food safety and public health. Meat processing plants may harbor various microorganisms and occasional foodborne pathogens; thus, the environmental microbial community might impact pathogen survival via mixed biofilm formation. We collected floor drain samples from two beef plants with different E. coli O157:H7 prevalence history and investigated the effects of the environmental microorganisms on pathogen sanitizer tolerance. The results showed that biofilm forming ability and bacterial species composition varied considerably based on the plants and drain locations. E. coli O157:H7 cells obtained significantly higher sanitizer tolerance in mixed biofilms by samples from the plant with recurrent E. coli O157:H7 prevalence than those mixed with samples from the other plant. The mixed biofilm that best protected E. coli O157:H7 also had the highest species diversity. The percentages of the species were altered significantly after sanitization, suggesting that the community composition affects the role and tolerance level of each individual species. Therefore, the unique environmental microbial community, their ability to form biofilms on contact surfaces and the interspecies interactions all play roles in E. coli O157:H7 persistence by either enhancing or reducing pathogen survival within the biofilm community.

Air and surface contamination in non-health care settings among 641 environmental specimens of 39 COVID-19 cases.

Little is known about the SARS-CoV-2 contamination of environmental surfaces and air in non-health care settings among COVID-19 cases. We explored the SARS-CoV-2 contamination of environmental surfaces and air by collecting air and swabbing environmental surfaces among 39 COVID-19 cases in Guangzhou, China. The specimens were tested on RT-PCR. The information collected for COVID-19 cases included basic demographic, clinical severity, symptoms at onset, radiological testing, laboratory testing and hospital admission. A total of 641 environmental surfaces and air specimens were collected among 39 COVID-19 cases before disinfection. Among them, 20 specimens (20/641, 3.1%) were tested positive from 9 COVID-19 cases (9/39, 23.1%), with 5 (5/101, 5.0%) positive specimens from 3 asymptomatic cases, 5 (5/220, 2.3%) from 3 mild cases, and 10 (10/374, 2.7%) from 3 moderate cases. All positive specimens were collected within 3 days after diagnosis, and 10 (10/42, 23.8%) were found in toilet (5 on toilet bowl, 4 on sink/faucet/shower, 1 on floor drain), 4 (4/21, 19.0%) in anteroom (2 on water dispenser/cup/bottle, 1 on chair/table, 1 on TV remote), 1 (1/8, 12.5%) in kitchen (1 on dining-table), 1 (1/18, 5.6%) in bedroom (1 on bed/sheet pillow/bedside table), 1 (1/5, 20.0%) in car (1 on steering wheel/seat/handlebar) and 3 (3/20, 21.4%) on door knobs. Air specimens in room (0/10, 0.0%) and car (0/1, 0.0%) were all negative. SARS-CoV-2 was found on environmental surfaces especially in toilet, and may survive for several days. We provided evidence of potential for SARS-CoV-2 transmission through contamination of environmental surfaces.