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1.
Appl Environ Microbiol ; 90(2): e0155323, 2024 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-38259079

RESUMO

Anti-viral surface coatings are under development to prevent viral fomite transmission from high-traffic touch surfaces in public spaces. Copper's anti-viral properties have been widely documented, but the anti-viral mechanism of copper surfaces is not fully understood. We screened a series of metal and metal oxide surfaces for anti-viral activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease (COVID-19). Copper and copper oxide surfaces exhibited superior anti-SARS-CoV-2 activity; however, the level of anti-viral activity was dependent on the composition of the carrier solution used to deliver virus inoculum. We demonstrate that copper ions released into solution from test surfaces can mediate virus inactivation, indicating a copper ion dissolution-dependent anti-viral mechanism. The level of anti-viral activity is, however, not dependent on the amount of copper ions released into solution per se. Instead, our findings suggest that degree of virus inactivation is dependent on copper ion complexation with other biomolecules (e.g., proteins/metabolites) in the virus carrier solution that compete with viral components. Although using tissue culture-derived virus inoculum is experimentally convenient to evaluate the anti-viral activity of copper-derived test surfaces, we propose that the high organic content of tissue culture medium reduces the availability of "uncomplexed" copper ions to interact with the virus, negatively affecting virus inactivation and hence surface anti-viral performance. We propose that laboratory anti-viral surface testing should include virus delivered in a physiologically relevant carrier solution (saliva or nasal secretions when testing respiratory viruses) to accurately predict real-life surface anti-viral performance when deployed in public spaces.IMPORTANCEThe purpose of evaluating the anti-viral activity of test surfaces in the laboratory is to identify surfaces that will perform efficiently in preventing fomite transmission when deployed on high-traffic touch surfaces in public spaces. The conventional method in laboratory testing is to use tissue culture-derived virus inoculum; however, this study demonstrates that anti-viral performance of test copper-containing surfaces is dependent on the composition of the carrier solution in which the virus inoculum is delivered to test surfaces. Therefore, we recommend that laboratory surface testing should include virus delivered in a physiologically relevant carrier solution to accurately predict real-life test surface performance in public spaces. Understanding the mechanism of virus inactivation is key to future rational design of improved anti-viral surfaces. Here, we demonstrate that release of copper ions from copper surfaces into small liquid droplets containing SARS-CoV-2 is a mechanism by which the virus that causes COVID-19 can be inactivated.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , Cobre/farmacologia , Antivirais , Óxidos , Íons
2.
J Formos Med Assoc ; 123(1): 45-54, 2024 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-37625983

RESUMO

BACKGROUND: The role of environmental contamination in COVID-19 transmission within hospitals is still of interest due to the significant impact of outbreaks globally. However, there is a scarcity of data regarding the utilization of environmental sampling for informing infection control measures during SARS-CoV-2 outbreaks. METHODS: This retrospective study analyzed incident event investigations conducted at a single center from May 1, 2021, to August 31, 2021. Investigations were initiated following the identification of a COVID-19 confirmed case (referred to as the index case) who had stayed in a hospital area outside the dedicated COVID-19 ward/bed and without specific COVID-19 precautions. Measures to prevent intra-hospital spread included contact tracing, adjusted testing policies, isolation of confirmed cases, quarantine of close contacts, environmental disinfection, and PCR testing of environmental samples. RESULTS: Among the 18 incident events investigated, the index case was a healthcare personnel in 8 events, a patient in 8 events, and a caregiver in 2 events. The median number of confirmed COVID-19 cases within 14 days was 13 (IQR, 7-31) for events with SARS-CoV-2 RNA detected on environmental surfaces, compared to only one (IQR, 1-1.5) for events without surface contamination (P = 0.04). Environmental contamination was independently associated with a higher number of COVID-19 cases (P < 0.001). CONCLUSION: This study highlights environmental contamination as an indicator of the severity of incident events and provides a framework for incident event management, including a protocol for environmental sampling. Implementing these measures can help prevent the spread of COVID-19 within healthcare facilities.


Assuntos
COVID-19 , Humanos , COVID-19/epidemiologia , COVID-19/prevenção & controle , SARS-CoV-2 , RNA Viral , Taiwan/epidemiologia , Estudos Retrospectivos , Centros de Atenção Terciária
3.
J Med Virol ; 95(1): e28103, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36039831

RESUMO

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing the ongoing global coronavirus disease 2019 (COVID-19) pandemic, is believed to be transmitted primarily through respiratory droplets and aerosols. However, reports are increasing regarding the contamination of environmental surfaces, shared objects, and cold-chain foods with SARS-CoV-2 RNA and the possibility of environmental fomite transmission of the virus raises much concern and debate. This study summarizes the current knowledge regarding potential mechanisms of environmental transmission of SARS-CoV-2, including the prevalence of surface contamination in various settings, the viability and stability of the virus on surfaces or fomites, as well as environmental factors affecting virus viability and survival such as temperature and relative humidity. Instances of fomite transmission, including cold-chain food transmission, and the importance of fomite transmission in epidemics, are discussed. The knowledge gaps regarding fomite transmission of SARS-CoV-2 are also briefly analyzed.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , RNA Viral/genética , Aerossóis e Gotículas Respiratórios , Fômites
4.
Environ Sci Technol ; 57(28): 10193-10200, 2023 07 18.
Artigo em Inglês | MEDLINE | ID: mdl-37399494

RESUMO

The potential for masks to act as fomites in the transmission of SARS-CoV-2 has been suggested but not demonstrated experimentally or observationally. In this study, we aerosolized a suspension of SARS-CoV-2 in saliva and used a vacuum pump to pull the aerosol through six different types of masks. After 1 h at 28 °C and 80% RH, SARS-CoV-2 infectivity was not detectable on an N95 and surgical mask, was reduced by 0.7 log10 on a nylon/spandex mask, and was unchanged on a polyester mask and two different cotton masks when recovered by elution in a buffer. SARS-CoV-2 RNA remained stable for 1 h on all masks. We pressed artificial skin against the contaminated masks and detected the transfer of viral RNA but no infectious virus to the skin. The potential for masks contaminated with SARS-CoV-2 in aerosols to act as fomites appears to be less than indicated by studies involving SARS-CoV-2 in very large droplets.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , Máscaras , RNA Viral , Aerossóis e Gotículas Respiratórios
5.
Risk Anal ; 2023 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-37936539

RESUMO

Simulated exposure to severe acute respiratory syndrome coronavirus 2 in the environment was demonstrated based on the actual coronavirus disease 2019 cluster occurrence in an office, with a projected risk considering the likely transmission pathways via aerosols and fomites. A total of 35/85 occupants were infected, with the attack rate in the first stage as 0.30. It was inferred that the aerosol transmission at long-range produced the cluster at virus concentration in the saliva of the infected cases on the basis of the simulation, more than 108  PFU mL-1 . Additionally, all wearing masks effectiveness was estimated to be 61%-81% and 88%-95% reduction in risk for long-range aerosol transmission in the normal and fit state of the masks, respectively, and a 99.8% or above decline in risk of fomite transmission. The ventilation effectiveness for long-range aerosol transmission was also calculated to be 12%-29% and 36%-66% reductions with increases from one air change per hour (ACH) to two ACH and six ACH, respectively. Furthermore, the virus concentration reduction in the saliva to 1/3 corresponded to the risk reduction for long-range aerosol transmission by 60%-64% and 40%-51% with and without masks, respectively.

6.
Enferm Infecc Microbiol Clin ; 41(4): 235-237, 2023 Apr.
Artigo em Espanhol | MEDLINE | ID: mdl-35153355

RESUMO

Objective: To study the presence of SARS-CoV-2 on surfaces (high, medium and low contacts) and airs in non-sanitary spaces with high public influx to evaluate the risk of environmental contagion. Method: Surfaces and airs were analysed by RT-qPCR to detect the presence of SARS-CoV-2. Results: A total of 394 surfaces and air samples were obtained from spaces with high public influx such as offices, shopping centres and nursing homes. The virus was not detected in any of the samples analysed. Conclusion: Although we cannot emphatically conclude that there is no risk of environmental infection by SARS-CoV-2 in non-sanitary spaces, we can affirm that the risk is almost non- existent.

7.
J Infect Dis ; 226(9): 1608-1615, 2022 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-35512326

RESUMO

BACKGROUND: The contribution of droplet-contaminated surfaces for virus transmission has been discussed controversially in the context of the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic. More importantly, the risk of fomite-based transmission has not been systematically addressed. Therefore, the aim of this study was to evaluate whether confirmed hospitalized coronavirus disease 2019 (COVID-19) patients can contaminate stainless steel carriers by coughing or intensive moistening with saliva and to assess the risk of SARS-CoV-2 transmission upon detection of viral loads and infectious virus in cell culture. METHODS: We initiated a single-center observational study including 15 COVID-19 patients with a high baseline viral load (cycle threshold value ≤25). We documented clinical and laboratory parameters and used patient samples to perform virus culture, quantitative polymerase chain reaction, and virus sequencing. RESULTS: Nasopharyngeal and oropharyngeal swabs of all patients were positive for viral ribonucleic acid on the day of the study. Infectious SARS-CoV-2 could be isolated from 6 patient swabs (46.2%). After coughing, no infectious virus could be recovered, however, intensive moistening with saliva resulted in successful viral recovery from steel carriers of 5 patients (38.5%). CONCLUSIONS: Transmission of infectious SARS-CoV-2 via fomites is possible upon extensive moistening, but it is unlikely to occur in real-life scenarios and from droplet-contaminated fomites.


Assuntos
COVID-19 , Doenças Transmissíveis , Humanos , SARS-CoV-2 , Fômites , Pandemias , Carga Viral
8.
J Appl Microbiol ; 133(4): 2583-2598, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-35870145

RESUMO

AIMS: To determine the antimicrobial potency of a surface-anchored quaternary ammonium salt (SAQAS)-based biocide during in vitro wet and dry fomite assays and to determine the mechanism of killing bacteria on the surface. METHODS AND RESULTS: Wet and dry fomite assays were established in vitro for a commercially available biocide (SAQAS-A) applied to glass and low-density polyethylene (LDPE) surfaces. Both wet and dry fomite tests showed the active killing of Gram-positive and Gram-negative bacteria but not endospores. Assays measuring membrane permeability (ATP and DNA release), bacterial membrane potential and bacterial ROS production were correlated with the time-to-kill profiles to show SAQAS-A activity in suspension and applied to a surface. CONCLUSIONS: SAQAS-A is an effective biocide against model strains of vegetative bacteria. The killing mechanism for SAQAS-A observed minimal membrane depolarization, a surge in ROS production and assessment of membrane permeability supported the puncture of cells in both suspension and surface attachment, leading to cell death. SIGNIFICANCE AND IMPACT OF THE STUDY: SAQAS represents effective surface biocides against single challenges with bacteria through a mechanical killing ability that supports real-world application if their durability can be demonstrated to maintain residual activity.


Assuntos
Anti-Infecciosos , Desinfetantes , Trifosfato de Adenosina , Antibacterianos/farmacologia , Bactérias , Desinfetantes/farmacologia , Bactérias Gram-Negativas , Bactérias Gram-Positivas , Testes de Sensibilidade Microbiana , Polietileno/farmacologia , Compostos de Amônio Quaternário/farmacologia , Espécies Reativas de Oxigênio
9.
Infect Immun ; 89(8): e0071320, 2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-34031124

RESUMO

Streptococcus pneumoniae is an opportunistic pathogen that is a common cause of serious invasive diseases such as pneumonia, bacteremia, meningitis, and otitis media. Transmission of this bacterium has classically been thought to occur through inhalation of respiratory droplets and direct contact with nasal secretions. However, the demonstration that S. pneumoniae is desiccation tolerant and, therefore, environmentally stable for extended periods of time opens up the possibility that this pathogen is also transmitted via contaminated surfaces (fomites). To better understand the molecular mechanisms that enable S. pneumoniae to survive periods of desiccation, we performed a high-throughput transposon sequencing (Tn-seq) screen in search of genetic determinants of desiccation tolerance. We identified 42 genes whose disruption reduced desiccation tolerance and 45 genes that enhanced desiccation tolerance. The nucleotide excision repair pathway was the most enriched category in our Tn-seq results, and we found that additional DNA repair pathways are required for desiccation tolerance, demonstrating the importance of maintaining genome integrity after desiccation. Deletion of the nucleotide excision repair gene uvrA resulted in a delay in transmission between infant mice, indicating a correlation between desiccation tolerance and pneumococcal transmssion. Understanding the molecular mechanisms that enable pneumococcal persistence in the environment may enable targeting of these pathways to prevent fomite transmission, thereby preventing the establishment of new colonization and any resulting invasive disease.


Assuntos
Reparo do DNA , Elementos de DNA Transponíveis , Infecções Pneumocócicas/microbiologia , Streptococcus pneumoniae/genética , Adaptação Biológica , Animais , Suscetibilidade a Doenças , Interações Hospedeiro-Patógeno , Camundongos , Infecções Pneumocócicas/imunologia , Infecções Pneumocócicas/transmissão , Transdução de Sinais , Streptococcus pneumoniae/imunologia , Streptococcus pneumoniae/patogenicidade
10.
Appl Environ Microbiol ; 87(21): e0137121, 2021 10 14.
Artigo em Inglês | MEDLINE | ID: mdl-34406830

RESUMO

Phage Phi6 is an enveloped virus considered a possible nonpathogenic surrogate for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other viral pathogens in transmission studies. Larger input amounts of bacteriophage Phi6 are shown to delay and protect the phage from environmental decay, both when the phages are dried in plastic tubes and when they are stored in saline solution at 4°C. In contrast, when bacteriophage Phi6 is placed in LB (Luria-Bertani) growth medium (instead of saline) prior to placement on the plastic surface, the influence of the starting concentration on viral recovery is negligible. Protection is reflected in the phage half-lives at higher concentrations being longer than the half-lives at lower concentrations. Because experiments supporting the possibility of fomite transmission of SARS-CoV-2 and other viruses rely upon the survival of infectious virus following inoculation onto various surfaces, large initial amounts of input virus on a surface may generate artificially inflated survival times compared to realistic lower levels of virus that a subject would normally encounter. This is not only because there are extra half-lives to go through at higher concentrations but also because the half-lives themselves are extended at higher virus concentrations. It is important to design surface drying experiments for pathogens with realistic levels of input virus and to consider the role of the carrier and matrix if the results are to be clinically relevant. IMPORTANCE During the coronavirus disease 2019 (COVID-19) pandemic, much attention has been paid to the environmental decay of SARS-CoV-2 due to the proposed transmission of the virus via fomites. However, published experiments have commenced with inocula with very high virus titers, an experimental design not representative of real-life conditions. The study described here evaluated the impact of the initial virus titer on the environmental decay of an enveloped virus, using a nonpathogenic surrogate for the transmission of SARS-CoV-2, enveloped bacteriophage Phi6. We establish that higher concentrations of virus can protect the virus from environmental decay, depending on conditions. This has important implications for stability studies of SARS-CoV-2 and other viruses. Our results point to a limitation in the fundamental methodology that has been used to attribute fomite transmission for almost all respiratory viruses.


Assuntos
Bacteriófago phi 6 , Pseudomonas syringae/virologia , Meios de Cultura , Dessecação , Fômites/virologia , Meia-Vida , Plásticos , SARS-CoV-2 , Solução Salina , Temperatura , Inativação de Vírus
11.
Appl Environ Microbiol ; 87(13): e0065321, 2021 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-33931423

RESUMO

Controversy continues about the significance of fomite transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Recent papers continue to advocate concern. However, designs of studies showing virus survival on surfaces under laboratory conditions are unsuitable for extrapolation to real life. Although viral RNA is frequently found on real-life surfaces, actual tests for infectious virus are almost entirely negative, even in hospitals with COVID-19 patients. Fomite transmission should be regarded as no more than a very minor component of this pandemic.


Assuntos
COVID-19/transmissão , Fômites/virologia , SARS-CoV-2/isolamento & purificação , COVID-19/epidemiologia , Humanos , Viabilidade Microbiana , RNA Viral/isolamento & purificação , SARS-CoV-2/genética , SARS-CoV-2/fisiologia
12.
Indoor Air ; 30(1): 49-59, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31545534

RESUMO

Touching contaminated surfaces might lead to the spread of pathogens, that is, the fomite transmission route. Although hand- and surface-hygiene practices are potentially important non-pharmaceutical interventions for the fomite route, the two interventions have been mostly studied separately in the literature. In this study, we develop a new conceptual model based on the law of mass action, analyze the temporal diffusion of contaminated surfaces and hands, and verify the model with simulations in an assumed norovirus outbreak in a buffet restaurant. A quantitative hygiene criterion is developed for the required frequency of surface disinfection and hand hygiene to control the fomite transmission in indoor environments. To eliminate surface contaminations, the product of pathogen-removal rates (including hygiene and natural death) on hands and surfaces must be no smaller than that of the human hand and surface contact frequency (ie, the net removal product must be non-negative). When the net removal product is negative, the number of contaminated surfaces and hands would show a logistic growth trend and finally approach the equilibrium. Our approach sheds light into how to optimize the combined use of hand hygiene and environmental decontamination for the best effectiveness under different settings.


Assuntos
Desinfecção , Fômites , Higiene das Mãos , Descontaminação , Mãos , Desinfecção das Mãos , Humanos
13.
J Appl Microbiol ; 122(2): 522-530, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27660041

RESUMO

AIMS: The goal of this study was to explore various models for describing viral persistence (infectivity) on fomites and identify the best fit models. METHODS AND RESULTS: The persistence of poliovirus over time was studied on three different fomite materials: steel, cotton and plastic. Known concentrations of poliovirus type 1 were applied to the surface coupons in an indoor environment for various lengths of time. Viruses were recovered from the surfaces by vortexing in phosphate buffer. Seven different mathematical models of relative persistence over time were fit to the data, and the preferred model for each surface was selected based on the Bayesian information criterion. CONCLUSIONS: While the preferred model varied by fomite type, the virus showed a rapid initial decay on all of the fomite types, followed by a transition to a more gradual decay after about 4-8 days. Estimates of the time for 99% reduction ranged from 81 h for plastic to 143 h for cotton. A 6 log reduction of recoverable infectivity of poliovirus did not occur during the 3-week duration of the experiment for any of the fomites. SIGNIFICANCE AND IMPACT OF THE STUDY: In protected indoor environments poliovirus can remain infective for weeks. The models identified by this study can be used in risk assessments to identify appropriate strategies for managing this risk.


Assuntos
Fômites/virologia , Modelos Biológicos , Poliovirus/fisiologia , Animais , Teorema de Bayes , Linhagem Celular , Chlorocebus aethiops , Fômites/classificação , Humanos , Poliomielite/transmissão , Poliomielite/virologia
14.
Sci Rep ; 14(1): 6190, 2024 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-38486016

RESUMO

The COVID-19 pandemic has provided valuable lessons that deserve deep thought to prepare for the future. The decay pattern of surface contamination by SARS-CoV-2 RNA in the residences of COVID-19 patients is important but still unknown. We collected 2,233 surface samples from 21 categories of objects in 141 residences of COVID-19 patients in Shanghai when attacked by the omicron variant in spring 2022. Several characteristics of the patients and their residences were investigated to identify relevant associations. The decay of contamination was explored to determine the persistence. Approximately 8.7% of the surface samples were tested positive for SARS-CoV-2 RNA. The basin, water tap, and sewer inlet had the highest positive rates, all exceeding 20%. Only time was significantly associated with the level of surface contamination with SARS-CoV-2, showing a negative association. The decrease fit a first-order decay model with a decay rate of 0.77 ± 0.07 day-1, suggesting a 90% reduction in three days. Positive associations between the cumulative number of newly diagnosed patients in the same building and the positive rate of SARS-CoV-2 RNA in the public corridor were significant during the three days. Our results, in conjunction with the likely lower infectivity or viability, demonstrate that fomite transmission played a limited role in COVID-19 spread. The time determined SARS-CoV-2 RNA contamination, which was reduced by three days. This study is the first to show the decay patterns of SARS-CoV-2 contamination in real residential environments, providing insight into the patterns of transmission, as well as community-based prevention and control of similar threats.


Assuntos
COVID-19 , Humanos , COVID-19/epidemiologia , SARS-CoV-2/genética , RNA Viral/genética , Pandemias , China/epidemiologia
15.
Sci Total Environ ; 868: 161388, 2023 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-36621479

RESUMO

Since the broke out of the novel coronavirus disease at the end of 2019, nearly 650 million people have been infected around the globe, and >6.6 million have died from this disease. The first wave of infections in mainland China had been effectively controlled within a short period, with no domestic cases of infection for 56 consecutive days from April 16, 2020. Nonetheless, the re-emergence of several outbreaks in multiple Chinese cities posed a new challenge for public health authorities after new cases of infections were found in Xinfadi Market in Beijing on June 11, 2020. In the following series of re-emergent outbreaks, findings from epidemiological investigations suggested that more than twenty re-emergent outbreaks were caused by fomite transmission, predominantly via imported frozen and chilled foods contaminated by the SARS-CoV-2 virus. Seven of the eleven incidents involving frozen and chilled foods were identified by screening individuals with occupational exposure to imported cold-chain foods and associated individuals. Evidence showed that low temperatures and poor ventilation typically maintained through cold-chain logistics create amenable environments for the survival of SARS-CoV-2, making transnational cold chain logistics a congenial vehicle to spread the virus through global transport of consumer goods. To address this gap, here we present a scrutiny of the findings from epidemiological investigations in recent re-emergent outbreaks in China caused by fomite transmission via imported foods and goods. A national regime of traceable cold-chain foods and reinforced customs inspection protocols were established by public health authorities in mainland China as emergency responses to recurring outbreaks from fomite transmission via imported goods. We urge that more attention needs to be given to this specific route of pathogenic transmission to ensure biosecurity and to increase the preparedness for epidemic or pandemic scenarios by the global food industry and logistics carriers.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , COVID-19/epidemiologia , China/epidemiologia , Surtos de Doenças , Pandemias/prevenção & controle
16.
Enferm Infecc Microbiol Clin (Engl Ed) ; 41(4): 235-237, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36167639

RESUMO

OBJECTIVE: To study the presence of SARS-CoV-2 on surfaces (high, medium and low contact) and airs in non-sanitary spaces with high public influx to evaluate the risk of environmental contagion. METHODS: Surfaces and airs were analysed by RT-qPCR to detect the presence of SARS-CoV-2. RESULTS: 394 surfaces and air samples were obtained from spaces with high public influx such as offices, shopping centres and nursing homes. The virus was not detected in any of the samples analysed. CONCLUSION: Although we cannot emphatically conclude that there is no risk of environmental 27 infection by SARS-CoV-2 in non-sanitary spaces, we can affirm that the risk is almost non- existent.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , Risco
17.
PeerJ ; 11: e16420, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38025703

RESUMO

During the recent pandemic of COVID-19 (SARS-CoV-2), influential public health agencies such as the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) have favored the view that SARS CoV-2 spreads predominantly via droplets. Many experts in aerobiology have openly opposed that stance, forcing a vigorous debate on the topic. In this review, we discuss the various proposed modes of viral transmission, stressing the interdependencies between droplet, aerosol, and fomite spread. Relative humidity and temperature prevailing determine the rates at which respiratory aerosols and droplets emitted from an expiratory event (sneezing, coughing, etc.) evaporate to form smaller droplets or aerosols, or experience hygroscopic growth. Gravitational settling of droplets may result in contamination of environmental surfaces (fomites). Depending upon human, animal and mechanical activities in the occupied space indoors, viruses deposited on environmental surfaces may be re-aerosolized (re-suspended) to contribute to aerosols, and can be conveyed on aerial particulate matter such as dust and allergens. The transmission of respiratory viruses may then best be viewed as resulting from dynamic virus spread from infected individuals to susceptible individuals by various physical states of active respiratory emissions, instead of the current paradigm that emphasizes separate dissemination by respiratory droplets, aerosols or by contaminated fomites. To achieve the optimum outcome in terms of risk mitigation and infection prevention and control (IPAC) during seasonal infection peaks, outbreaks, and pandemics, this holistic view emphasizes the importance of dealing with all interdependent transmission modalities, rather than focusing on one modality.


Assuntos
COVID-19 , Aerossóis e Gotículas Respiratórios , Estados Unidos , Humanos , COVID-19/epidemiologia , SARS-CoV-2 , Fômites , Poeira
18.
J Hazard Mater ; 425: 128051, 2022 03 05.
Artigo em Inglês | MEDLINE | ID: mdl-34910996

RESUMO

The number of people infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to increase worldwide, but despite extensive research, there remains significant uncertainty about the predominant routes of SARS-CoV-2 transmission. We conducted a mechanistic modeling and calculated the exposure dose and infection risk of each passenger in a two-bus COVID-19 outbreak in Hunan province, China. This outbreak originated from a single pre-symptomatic index case. Some human behavioral data related to exposure including boarding and alighting time of some passengers and seating position and mask wearing of all passengers were obtained from the available closed-circuit television images/clips and/or questionnaire survey. Least-squares fitting was performed to explore the effect of effective viral load on transmission risk, and the most likely quanta generation rate was also estimated. This study reveals the leading role of airborne SARS-CoV-2 transmission and negligible role of fomite transmission in a poorly ventilated indoor environment, highlighting the need for more targeted interventions in such environments. The quanta generation rate of the index case differed by a factor of 1.8 on the two buses and transmission occurred in the afternoon of the same day, indicating a time-varying effective viral load within a short period of five hours.


Assuntos
Microbiologia do Ar , COVID-19 , Fômites/virologia , Veículos Automotores , SARS-CoV-2 , COVID-19/transmissão , Surtos de Doenças , Humanos
19.
Bull Natl Res Cent ; 46(1): 245, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36156873

RESUMO

Background: The global community has battled the spread of SAR-CoV-2 for almost 2 years, and the projection is that the virus may be recurrent like the seasonal flu. The SARS-CoV-2 pandemic disrupted activities within the food supply chain that cost billions of dollars globally. This has heightened concerns about fomite spread of the virus through surfaces. There is an urgent need to understand the risk portends by this virus along the produce supply chain with conditions (low temperature and high relative humidity) conducive to extended survival of the virus. Main body: Pre-dating SARS-CoV-2 are other types of coronaviruses that had lower infection and mortality rates. There are some similarities between the former and the new coronavirus, especially with regards to transmission modes and their survivability on surfaces. There is evidence of other coronaviruses' survival on surfaces for weeks. Currently, there are limited evidence-based studies to enlighten us on how the virus is transmitted within the produce supply chain. A few studies claim that the virus could spread through the cold supply chains. However, these are not sufficient to make a conclusive inference about the deadly SARS-CoV-2. Conclusions: This paper provides a succinct review of the literature on current understanding of the transmission, survivability, and risk SARS-CoV-2 portend to humans within the produce supply chain and calls for more evidence-based research to allay or alert us of the potential risk of fomite transmission of SARS-CoV-2. The paper also highlights examples of conventional and novel non-thermal inactivation and sanitation methods applicable to this type of virus.

20.
J Hazard Mater ; 424(Pt B): 127511, 2022 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-34688007

RESUMO

Contaminants, such as pathogens or non-living substances, can spread through the interaction of their carriers (e.g., air and surfaces), which constitute a network. The structure of such networks plays an important role in the contaminant spread. We measured the contaminant spreading efficiency in different networks using a newly defined parameter. We analyzed basic networks to identify the effect of the network structure on the contaminant spread. The spreading efficiency was highly related to some network parameters, such as the source node's average path length and degree, and considerably varied with the transfer rate per inter-node interaction. We compared the contaminant spreading efficiencies in some complex networks, namely scale-free, random, regular-lattice, and bipartite networks, with centralized, linear, and fractal networks. The contaminant spreading was particularly efficient in the fractal network when the transfer rate was ~0.5. Two categories of experiments were performed to validate the effect of the network structure on contaminant spreading in practical cases: (I) gas diffusion in multi-compartment cabins (II) bacteria transfer in multi-finger networks. The gas diffusion could be well estimated based on the diffusion between two compartments, and it was considerably affected by the network structure. Meanwhile, the bacteria spread was generally less efficient than expected.


Assuntos
Modelos Teóricos , Difusão
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