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1.
Proc Natl Acad Sci U S A ; 119(4)2022 01 25.
Article in English | MEDLINE | ID: covidwho-1642082

ABSTRACT

The phase state of respiratory aerosols and droplets has been linked to the humidity-dependent survival of pathogens such as SARS-CoV-2. To inform strategies to mitigate the spread of infectious disease, it is thus necessary to understand the humidity-dependent phase changes associated with the particles in which pathogens are suspended. Here, we study phase changes of levitated aerosols and droplets composed of model respiratory compounds (salt and protein) and growth media (organic-inorganic mixtures commonly used in studies of pathogen survival) with decreasing relative humidity (RH). Efflorescence was suppressed in many particle compositions and thus unlikely to fully account for the humidity-dependent survival of viruses. Rather, we identify organic-based, semisolid phase states that form under equilibrium conditions at intermediate RH (45 to 80%). A higher-protein content causes particles to exist in a semisolid state under a wider range of RH conditions. Diffusion and, thus, disinfection kinetics are expected to be inhibited in these semisolid states. These observations suggest that organic-based, semisolid states are an important consideration to account for the recovery of virus viability at low RH observed in previous studies. We propose a mechanism in which the semisolid phase shields pathogens from inactivation by hindering the diffusion of solutes. This suggests that the exogenous lifetime of pathogens will depend, in part, on the organic composition of the carrier respiratory particle and thus its origin in the respiratory tract. Furthermore, this work highlights the importance of accounting for spatial heterogeneities and time-dependent changes in the properties of aerosols and droplets undergoing evaporation in studies of pathogen viability.


Subject(s)
Calcium Chloride/chemistry , Models, Chemical , SARS-CoV-2/chemistry , Serum Albumin/chemistry , Sodium Chloride/chemistry , COVID-19/virology , Diffusion , Disinfection/methods , Humans , Humidity , Kinetics , Microbial Viability , Phase Transition , Surface Properties
2.
Proc Natl Acad Sci U S A ; 118(49)2021 12 07.
Article in English | MEDLINE | ID: covidwho-1541316

ABSTRACT

As coronaviruses (CoVs) replicate in the host cell cytoplasm, they rely on their own capping machinery to ensure the efficient translation of their messenger RNAs (mRNAs), protect them from degradation by cellular 5' exoribonucleases (ExoNs), and escape innate immune sensing. The CoV nonstructural protein 14 (nsp14) is a bifunctional replicase subunit harboring an N-terminal 3'-to-5' ExoN domain and a C-terminal (N7-guanine)-methyltransferase (N7-MTase) domain that is presumably involved in viral mRNA capping. Here, we aimed to integrate structural, biochemical, and virological data to assess the importance of conserved N7-MTase residues for nsp14's enzymatic activities and virus viability. We revisited the crystal structure of severe acute respiratory syndrome (SARS)-CoV nsp14 to perform an in silico comparative analysis between betacoronaviruses. We identified several residues likely involved in the formation of the N7-MTase catalytic pocket, which presents a fold distinct from the Rossmann fold observed in most known MTases. Next, for SARS-CoV and Middle East respiratory syndrome CoV, site-directed mutagenesis of selected residues was used to assess their importance for in vitro enzymatic activity. Most of the engineered mutations abolished N7-MTase activity, while not affecting nsp14-ExoN activity. Upon reverse engineering of these mutations into different betacoronavirus genomes, we identified two substitutions (R310A and F426A in SARS-CoV nsp14) abrogating virus viability and one mutation (H424A) yielding a crippled phenotype across all viruses tested. Our results identify the N7-MTase as a critical enzyme for betacoronavirus replication and define key residues of its catalytic pocket that can be targeted to design inhibitors with a potential pan-coronaviral activity spectrum.


Subject(s)
Exoribonucleases/chemistry , Models, Molecular , Protein Conformation , Viral Nonstructural Proteins/chemistry , Amino Acid Sequence , Base Sequence , Binding Sites , Catalytic Domain , Conserved Sequence , Exoribonucleases/genetics , Exoribonucleases/metabolism , Microbial Viability , Nucleotide Motifs , RNA, Viral/chemistry , RNA, Viral/genetics , RNA-Binding Proteins , Structure-Activity Relationship , Viral Nonstructural Proteins/genetics , Viral Nonstructural Proteins/metabolism , Virus Replication/genetics
4.
J Clin Epidemiol ; 142: 38-44, 2022 02.
Article in English | MEDLINE | ID: covidwho-1487821

ABSTRACT

OBJECTIVE: To evaluate the effectiveness of the Pfizer BNT162b2 vaccine against the SARS-Cov-2 Beta variant. STUDY DESIGN AND SETTING: Israel's mass vaccination program, using two doses of the Pfizer BNT162b2 vaccine, successfully curtailed the Alpha variant outbreak during winter 2020-2021, However, the virus may mutate and partially evade the immune system. To monitor this, sequencing of selected positive swab samples of interest was initiated. Comparing vaccinated with unvaccinated PCR positive persons, we estimated the odds ratio for a vaccinated case to have the Beta vs. the Alpha variant, using logistic regression, controlling for important confounders. RESULTS: There were 19 cases of Beta variant (3.2%) among those vaccinated more than 14 days before the positive sample and 79 (3.4%) among the unvaccinated. The estimated odds ratio was 1.26 (95% CI: 0.65-2.46). Assuming the effectiveness against the Alpha variant to be 95%, the estimated effectiveness against the Beta variant was 94% (95% CI: 88%-98%). CONCLUSION: Despite concerns over the Beta variant, the BNT162b2 vaccine seemed to provide substantial immunity against both the Beta and the Alpha variants. From 14 days following the second vaccine dose, the effectiveness of BNT162b2 vaccine was at most marginally affected by the Beta variant.


Subject(s)
/administration & dosage , COVID-19/virology , RNA, Viral/genetics , SARS-CoV-2/classification , Sequence Analysis, RNA/methods , Adult , Aged , Aged, 80 and over , COVID-19/prevention & control , Female , High-Throughput Nucleotide Sequencing , Humans , Israel , Logistic Models , Male , Mass Vaccination , Microbial Viability/drug effects , Middle Aged , SARS-CoV-2/drug effects , SARS-CoV-2/genetics , SARS-CoV-2/growth & development , Young Adult
5.
Braz. dent. sci ; 24(4): 1-13, 2021. tab, ilus, graf
Article in English | WHO COVID, LILACS (Americas) | ID: covidwho-1471186

ABSTRACT

Objective: Dentists need a high level of awareness to limit the spread of COVID-19 (Coronavirus disease 2019). This study aimed to evaluate the level of awareness and attitude regarding the risk associated with dental procedures among dentists. Material and Methods: An online questionnaire was submitted to dentists between April- May 2020. The questionnaire form included questions related to demographic data, the transmission characterization of SARS-CoV-2, and treatment of COVID-19 patients. Data were analyzed using IBM SPSS V23 and chi-square test (p ≤ 0.05). Results: A total of 3825 participants (29.1± 7.6 years) were included. In COVID-19, the riskiest dental branch in terms of the risk of contamination through saliva was considered to be Periodontics (32.2%), while the least risky branch was Orthodontics (0.2%). Specific dental treatment procedures considered at high risk of contamination were tooth preparation (69.4%), scaling and root planing (63.5%), filling (53.4%), and pulpectomy (40.5%). The parameters of the study that differed according to gender and professional status were the viability of the virus, the risk assessment, saliva contamination risk, and aerosol-generating activities for COVID-19 (p < 0.05). Conclusion: Dentists were aware of the risk assessment and extra precautionary methods. However, they had limited knowledge about the viability of the virus. Dentists should be aware of recommended approaches and update their knowledge about COVID-19 to limit the spread of the disease. Since dentistry is an area suitable for the transmission of the COVID-19, the fact that dentists have information about the viability of this virus will be lifesaving in clinical applications (AU)


Objetivo: Os dentistas precisam de um alto nível de conhecimento para limitar a disseminação de COVID-19 (doença por coronavírus 2019). Este estudo teve como objetivo avaliar o nível de consciência e atitude em relação ao risco associado aos procedimentos odontológicos entre os dentistas. Material e Métodos: Um questionário online foi submetido aos dentistas entre abril e maio de 2020. O formulário do questionário incluía questões relacionadas aos dados demográficos, à caracterização da transmissão da SARS-CoV-2 e ao tratamento de pacientes com COVID-19. Os dados foram analisados usando IBM SPSS V23 e teste do qui-quadrado (p ≤ 0,05). Resultados:Um total de 3825 participantes (29,1 ± 7,6 anos) foram incluídos. Na COVID-19, o ramo odontológico de maior risco em termos de risco de contaminação pela saliva foi considerado a Periodontia (32,2%), enquanto o ramo de menor risco foi a Ortodontia (0,2%). Os procedimentos odontológicos específicos considerados de alto risco de contaminação foram preparo dentário (69,4%), raspagem e alisamento radicular (63,5%), obturação (53,4%) e pulpectomia (40,5%). Os parâmetros do estudo que diferiram de acordo com sexo e status profissional foram a viabilidade do vírus, a avaliação de risco, risco de contaminação da saliva e atividades geradoras de aerossol para COVID-19 (p <0,05). Conclusão: Os dentistas estão cientes da avaliação de risco e dos métodos de precaução extra. No entanto, eles tinham conhecimento limitado sobre a viabilidade do vírus. Os dentistas devem estar cientes das abordagens recomendadas e atualizar seus conhecimentos sobre COVID-19 para limitar a propagação da doença. Como a odontologia é uma área propícia para a transmissão da COVID-19, se dentistas tiverem informações sobre a viabilidade desse vírus poderão salvar vidas em aplicações clínicas. (AU)


Subject(s)
Humans , Risk , Dentistry , Microbial Viability , SARS-CoV-2 , COVID-19
6.
Appl Environ Microbiol ; 87(14): e0052621, 2021 06 25.
Article in English | MEDLINE | ID: covidwho-1408384

ABSTRACT

The transmission of SARS-CoV-2 is likely to occur through a number of routes, including contact with contaminated surfaces. Many studies have used reverse transcription-PCR (RT-PCR) analysis to detect SARS-CoV-2 RNA on surfaces, but seldom has viable virus been detected. This paper investigates the viability over time of SARS-CoV-2 dried onto a range of materials and compares viability of the virus to RNA copies recovered and whether virus viability is concentration dependent. Viable virus persisted for the longest time on surgical mask material and stainless steel, with a 99.9% reduction in viability by 122 and 114 h, respectively. Viability of SARS-CoV-2 reduced the fastest on a polyester shirt, with a 99.9% reduction within 2.5 h. Viability on the bank note was reduced second fastest, with 99.9% reduction in 75 h. RNA on all surfaces exhibited a 1-log reduction in genome copy number recovery over 21 days. The findings show that SARS-CoV-2 is most stable on nonporous hydrophobic surfaces. RNA is highly stable when dried on surfaces, with only 1-log reduction in recovery over 3 weeks. In comparison, SARS-CoV-2 viability reduced more rapidly, but this loss in viability was found to be independent of starting concentration. Expected levels of SARS-CoV-2 viable environmental surface contamination would lead to undetectable levels within 2 days. Therefore, when RNA is detected on surfaces, it does not directly indicate the presence of viable virus, even at low cycle threshold values. IMPORTANCE This study shows the impact of material type on the viability of SARS-CoV-2 on surfaces. It demonstrates that the decay rate of viable SARS-CoV-2 is independent of starting concentration. However, RNA shows high stability on surfaces over extended periods. This has implications for interpretation of surface sampling results using RT-PCR to determine the possibility of viable virus from a surface, where RT-PCR is not an appropriate technique to determine viable virus. Unless sampled immediately after contamination, it is difficult to align RNA copy numbers to quantity of viable virus on a surface.


Subject(s)
COVID-19 , Fomites/virology , Personal Protective Equipment/virology , RNA, Viral/isolation & purification , SARS-CoV-2/isolation & purification , COVID-19/epidemiology , COVID-19/transmission , COVID-19/virology , Humans , Microbial Viability , Surface Properties
7.
Am J Trop Med Hyg ; 104(2): 549-551, 2020 Dec 22.
Article in English | MEDLINE | ID: covidwho-1389662

ABSTRACT

We modeled the stability of SARS-CoV-2 on personal protective equipment (PPE) commonly worn in hospitals when carrying out high-risk airway procedures. Evaluated PPE included the visors and hoods of two brands of commercially available powered air purifying respirators, a disposable face shield, and Tyvek coveralls. Following an exposure to 4.3 log10 plaque-forming units (PFUs) of SARS-CoV-2, all materials displayed a reduction in titer of > 4.2 log10 by 72 hours postexposure, with detectable titers at 72 hours varying by material (1.1-2.3 log10 PFU/mL). Our results highlight the need for proper doffing and disinfection of PPE, or disposal, to reduce the risk of SARS-CoV-2 contact or fomite transmission.


Subject(s)
COVID-19/transmission , Gloves, Protective/virology , Microbial Viability , Personal Protective Equipment/virology , Respiratory Protective Devices/virology , SARS-CoV-2/physiology , COVID-19/virology , Half-Life , Humans , Infectious Disease Transmission, Patient-to-Professional
9.
Sci Rep ; 10(1): 22419, 2020 12 29.
Article in English | MEDLINE | ID: covidwho-1387458

ABSTRACT

Survival of respiratory viral pathogens in expelled saliva microdroplets is central to their transmission, yet the factors that determine survival in such microdroplets are not well understood. Here we combine microscopy imaging with virus viability assays to study survival of three bacteriophages suggested as good models for respiratory pathogens: the enveloped Phi6 (a surrogate for SARS-CoV-2), and the non-enveloped PhiX174 and MS2. We measured virus viability in human saliva microdroplets, SM buffer, and water following deposition on glass surfaces at various relative humidities (RH). Saliva and water microdroplets dried out rapidly, within minutes, at all tested RH levels (23%, 43%, 57%, and 78%), while SM microdroplets remained hydrated at RH ≥ 57%. Generally, the survival of all three viruses in dry saliva microdroplets was significantly greater than those in SM buffer and water under all RH (except PhiX174 in water under 57% RH survived the best among 3 media). Thus, atmosphere RH and microdroplet hydration state are not sufficient to explain virus survival, indicating that the virus-suspended medium, and association with saliva components in particular, likely play a role in virus survival. Uncovering the exact properties and components that make saliva a favorable environment for the survival of viruses, in particular enveloped ones like Phi6, is thus of great importance for reducing transmission of viral respiratory pathogens including SARS-CoV-2.


Subject(s)
Bacteriophage phi X 174/metabolism , Levivirus/metabolism , Microbial Viability , SARS-CoV-2/metabolism , Saliva/virology , Bacteriophage phi 6/metabolism , COVID-19/transmission , Environmental Microbiology , Humans , Viral Plaque Assay , Virus Inactivation
11.
Science ; 373(6558)2021 08 27.
Article in English | MEDLINE | ID: covidwho-1376452

ABSTRACT

The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols-how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.


Subject(s)
Air Microbiology , COVID-19/transmission , Respiratory Tract Infections/transmission , SARS-CoV-2 , Virus Diseases/transmission , Virus Physiological Phenomena , Aerosols , COVID-19/virology , Disease Transmission, Infectious , Humans , Microbial Viability , Particle Size , Respiratory System/virology , Respiratory Tract Infections/virology , SARS-CoV-2/isolation & purification , SARS-CoV-2/physiology , Viral Load , Virus Diseases/virology , Viruses/isolation & purification
13.
Eur J Epidemiol ; 36(7): 685-707, 2021 Jul.
Article in English | MEDLINE | ID: covidwho-1326830

ABSTRACT

Coronavirus disease (COVID-19) is a respiratory disease affecting many people and able to be transmitted through direct and perhaps indirect contact. Direct contact transmission, mediated by aerosols or droplets, is widely demonstrated, whereas indirect transmission is only supported by collateral evidence such as virus persistence on inanimate surfaces and data from other similar viruses. The present systematic review aims to estimate SARS-CoV-2 prevalence on inanimate surfaces, identifying risk levels according to surface characteristics. Data were obtained from studies in published papers collected from two databases (PubMed and Embase) with the last search on 1 September 2020. Included studies had to be papers in English, had to deal with coronavirus and had to consider inanimate surfaces in real settings. Studies were coded according to our assessment of the risk that the investigated surfaces could be contaminated by SARS-CoV-2. A meta-analysis and a metaregression were carried out to quantify virus RNA prevalence and to identify important factors driving differences among studies. Thirty-nine out of forty retrieved paper reported studies carried out in healthcare settings on the prevalence of virus RNA, five studies carry out also analyses through cell culture and six tested the viability of isolated viruses. Overall prevalences of SARS-CoV-2 RNA on high-, medium- and low-risk surfaces were 0.22 (CI95 [0.152-0.296]), 0.04 (CI95 [0.007-0.090]), and 0.00 (CI95 [0.00-0.019]), respectively. The duration surfaces were exposed to virus sources (patients) was the main factor explaining differences in prevalence.


Subject(s)
COVID-19 , Equipment Contamination , Fomites/virology , RNA, Viral/isolation & purification , SARS-CoV-2/isolation & purification , Humans , Microbial Viability , Prevalence
14.
Microbiol Spectr ; 9(1): e0033321, 2021 09 03.
Article in English | MEDLINE | ID: covidwho-1319385

ABSTRACT

We studied the stability of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) under different simulated outdoor conditions by changing the temperature (20°C and 35°C), the illuminance (darkness, 10 klx, and 56 klx), and/or the cleanness of the surfaces at 50% relative humidity (RH). In darkness, the loss of viability of the virus on stainless steel is temperature dependent, but this is hidden by the effect of the sunlight from the first minutes of exposure. The virus shows a sensitivity to sunlight proportional to the illuminance intensity of the sunlight. The presence of interfering substances has a moderate effect on virus viability even with an elevated illuminance. Thus, SARS-CoV-2 is rapidly inactivated by simulated sunlight in the presence or absence of high levels of interfering substances at 20°C or 35°C and 50% relative humidity. IMPORTANCE Clinical matrix contains high levels of interfering substances. This study is the first to reveal that the presence of high levels of interfering substances had little impact on the persistence of SARS-CoV-2 on stainless steel following exposure to simulated sunlight. Thus, SARS-CoV-2 should be rapidly inactivated in outdoor environments in the presence or absence of interfering substances. Our results indicate that transmission of SARS-CoV-2 is unlikely to occur through outdoor surfaces, dependent on illuminance intensity. Moreover, most studies are interested in lineage S of SARS-CoV-2. In our experiments, we studied the stability of L-type strains, which comprise the majority of strains isolated from worldwide patients. Nevertheless, the effect of sunlight seems to be similar regardless of the strain studied, suggesting that the greater spread of certain variants is not correlated with better survival in outdoor conditions.


Subject(s)
Microbial Viability/radiation effects , SARS-CoV-2/radiation effects , Sunlight , Virus Inactivation/radiation effects , COVID-19/prevention & control , COVID-19/transmission , Decontamination , Humans , Kinetics , SARS-CoV-2/growth & development , Surface Properties , Temperature
15.
PLoS One ; 16(1): e0244885, 2021.
Article in English | MEDLINE | ID: covidwho-1251754

ABSTRACT

Human influenza virus infections occur annually worldwide and are associated with high morbidity and mortality. Hence, development of novel anti-influenza drugs is urgently required. Rice Power® extract developed by the Yushin Brewer Co. Ltd. is a novel aqueous extract of rice obtained via saccharization and fermentation with various microorganisms, such as Aspergillus oryzae, yeast [such as Saccharomyces cerevisiae], and lactic acid bacteria, possessing various biological and pharmacological properties. In our previous experimental screening with thirty types of Rice Power® extracts, we observed that the 30th Rice Power® (Y30) extract promoted the survival of influenza A virus-infected Madin-Darby canine kidney (MDCK) cells. Therefore, to identify compounds for the development of novel anti-influenza drugs, we aimed to investigate whether the Y30 extract exhibits anti-influenza A virus activity. In the present study, we demonstrated that the Y30 extract strongly promoted the survival of influenza A H1N1 Puerto Rico 8/34 (A/PR/8/34), California 7/09, or H3N2 Aichi 2/68 (A/Aichi/2/68) viruses-infected MDCK cells and inhibited A/PR/8/34 or A/Aichi/2/68 viruses infection and growth in the co-treatment and pre-infection experiments. The pre-treatment of Y30 extract on MDCK cells did not induce anti-influenza activity in the cell. The Y30 extract did not significantly affect influenza A virus hemagglutination, and neuraminidase and RNA-dependent RNA polymerase activities. Interestingly, the electron microscopy experiment revealed that the Y30 extract disrupts the integrity of influenza A virus particles by permeabilizing the viral membrane envelope, suggesting that Y30 extract has a direct virucidal effect against influenza A virus. Furthermore, we observed that compared to the ethyl acetate (EtOAc) extract, the water extract of Y30 extract considerably promoted the survival of cells infected with A/PR/8/34 virus. These results indicated that more anti-influenza components were present in the water extract of Y30 extract than in the EtOAc extract. Our results highlight the potential of a rice extract fermented with A. oryzae and S. cerevisiae as an anti-influenza medicine and a drug source for the development of anti-influenza compounds.


Subject(s)
Aspergillus oryzae/metabolism , Influenza A virus/drug effects , Oryza/chemistry , Oryza/microbiology , Plant Extracts/pharmacology , Saccharomyces cerevisiae/metabolism , Water/chemistry , Acetates/chemistry , Animals , Antiviral Agents/pharmacology , Dogs , Fermentation , Influenza A virus/growth & development , Influenza A virus/physiology , Madin Darby Canine Kidney Cells , Microbial Viability/drug effects
16.
Appl Environ Microbiol ; 87(13): e0065321, 2021 06 11.
Article in English | MEDLINE | ID: covidwho-1290539

ABSTRACT

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.


Subject(s)
COVID-19/transmission , Fomites/virology , SARS-CoV-2/isolation & purification , COVID-19/epidemiology , Humans , Microbial Viability , RNA, Viral/isolation & purification , SARS-CoV-2/genetics , SARS-CoV-2/physiology
17.
Appl Environ Microbiol ; 87(14): e0052621, 2021 06 25.
Article in English | MEDLINE | ID: covidwho-1288347

ABSTRACT

The transmission of SARS-CoV-2 is likely to occur through a number of routes, including contact with contaminated surfaces. Many studies have used reverse transcription-PCR (RT-PCR) analysis to detect SARS-CoV-2 RNA on surfaces, but seldom has viable virus been detected. This paper investigates the viability over time of SARS-CoV-2 dried onto a range of materials and compares viability of the virus to RNA copies recovered and whether virus viability is concentration dependent. Viable virus persisted for the longest time on surgical mask material and stainless steel, with a 99.9% reduction in viability by 122 and 114 h, respectively. Viability of SARS-CoV-2 reduced the fastest on a polyester shirt, with a 99.9% reduction within 2.5 h. Viability on the bank note was reduced second fastest, with 99.9% reduction in 75 h. RNA on all surfaces exhibited a 1-log reduction in genome copy number recovery over 21 days. The findings show that SARS-CoV-2 is most stable on nonporous hydrophobic surfaces. RNA is highly stable when dried on surfaces, with only 1-log reduction in recovery over 3 weeks. In comparison, SARS-CoV-2 viability reduced more rapidly, but this loss in viability was found to be independent of starting concentration. Expected levels of SARS-CoV-2 viable environmental surface contamination would lead to undetectable levels within 2 days. Therefore, when RNA is detected on surfaces, it does not directly indicate the presence of viable virus, even at low cycle threshold values. IMPORTANCE This study shows the impact of material type on the viability of SARS-CoV-2 on surfaces. It demonstrates that the decay rate of viable SARS-CoV-2 is independent of starting concentration. However, RNA shows high stability on surfaces over extended periods. This has implications for interpretation of surface sampling results using RT-PCR to determine the possibility of viable virus from a surface, where RT-PCR is not an appropriate technique to determine viable virus. Unless sampled immediately after contamination, it is difficult to align RNA copy numbers to quantity of viable virus on a surface.


Subject(s)
COVID-19 , Fomites/virology , Personal Protective Equipment/virology , RNA, Viral/isolation & purification , SARS-CoV-2/isolation & purification , COVID-19/epidemiology , COVID-19/transmission , COVID-19/virology , Humans , Microbial Viability , Surface Properties
18.
Ann Biomed Eng ; 49(9): 2554-2565, 2021 Sep.
Article in English | MEDLINE | ID: covidwho-1287444

ABSTRACT

Ultraviolet radiation as a germicide is widely used in the health field and even in domestic hygiene. Here, we propose an improvement in low-cost portable units of filtration for indoor air, which is based on ultraviolet radiation. In the current technology, to carry out an air filtration with a suspension of aerosols in which there is a likely concentration of pathogens, whether viral, bacterial or molds, the air is forced to pass as close as possible to the ionizing radiation source (near field). Since the optical mass is very small, the desired effect can be achieved in a considerably short time, deactivating the infective potential of these biological agents. The proposal of this work is the regulation of the flow or speed control of passage through these filters by passive elements instead of by electronic control systems. For this, two devices have been designed, simulated, and built, obtaining similar net pathogen inactivation rates under different flow rates. The passive flow control device has demonstrated higher performance in terms of flow rate and lower cost of production since they do not require electronics and are produced with fewer diodes. This passive device has also shown a lower projection of maintenance cost, lower energy consumption rate (higher efficiency), and longer projection of useful life.


Subject(s)
Air Filters , Air Pollution, Indoor/prevention & control , COVID-19/prevention & control , Microbial Viability/radiation effects , SARS-CoV-2/chemistry , Ultraviolet Rays , Aerosols , Humans
19.
PLoS One ; 16(6): e0253068, 2021.
Article in English | MEDLINE | ID: covidwho-1264227

ABSTRACT

The novel coronavirus, SARS-CoV-2, has spread into a pandemic since its emergence in Wuhan, China in December of 2019. This has been facilitated by its high transmissibility within the human population and its ability to remain viable on inanimate surfaces for an extended period. To address the latter, we examined the effect of simulated sunlight on the viability of SARS-CoV-2 spiked into tissue culture medium or mucus. The study revealed that inactivation took 37 minutes in medium and 107 minutes in mucus. These times-to-inactivation were unexpected since they are longer than have been observed in other studies. From this work, we demonstrate that sunlight represents an effective decontamination method but the speed of decontamination is variable based on the underlying matrix. This information has an important impact on the development of infection prevention and control protocols to reduce the spread of this deadly pathogen.


Subject(s)
COVID-19/virology , Decontamination/methods , Mucus/virology , SARS-CoV-2/radiation effects , Sunlight , Virus Inactivation/radiation effects , Humans , Microbial Viability/radiation effects , SARS-CoV-2/physiology
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