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1.
EuropePMC; 2020.
Preprint in English | EuropePMC | ID: ppcovidwho-321774

ABSTRACT

When journalists cover a news story, they can cover the story from multiple angles or perspectives. A news article written about COVID-19 for example, might focus on personal preventative actions such as mask-wearing, while another might focus on COVID-19's impact on the economy. These perspectives are called "frames," which when used may influence public perception and opinion of the issue. We introduce a Web-based system for analyzing and classifying frames in text documents. Our goal is to make effective tools for automatic frame discovery and labeling based on topic modeling and deep learning widely accessible to researchers from a diverse array of disciplines. To this end, we provide both state-of-the-art pre-trained frame classification models on various issues as well as a user-friendly pipeline for training novel classification models on user-provided corpora. Researchers can submit their documents and obtain frames of the documents. The degree of user involvement is flexible: they can run models that have been pre-trained on select issues;submit labeled documents and train a new model for frame classification;or submit unlabeled documents and obtain potential frames of the documents. The code making up our system is also open-sourced and well-documented, making the system transparent and expandable. The system is available on-line at http://www.openframing.org and via our GitHub page https://github.com/davidatbu/openFraming .

2.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-313373

ABSTRACT

It is important to know whether SARS-CoV-2 is spread through the air-conditioning systems. Taking the central air-conditioning system as an example, we analyze the mechanism and potential health risk of respiratory virus transmission in air-conditioned rooms, and propose a method to study the risk of virus transmission in central air-conditioning systems by investigating the data from medical experiments. The virus carrying capacity and the decay characteristics of indoor pathogen droplets are studied in this research. Additionally, the effects of air temperature and relative humidity on the virus survival in the air or on surfaces are investigated. The removal efficiency of infectious droplet nuclei by air-conditioning filter was then determined. Thus, the transmission risk during the operation of centralized air-conditioning system is evaluated. The results show that the indoor temperature and humidity are controlled in the range of 20-25℃ and 40%-70% by central air-conditioning during the epidemic period, which not only benefits the health and comfort of residents, but also weakens the vitality of the virus. The larger the droplet size, the longer the viruses survive. Since the filter efficiency of air-conditioning filter increases with the increase of particle size, increasing the number of air changes of the circulating air volume can accelerate the removal of potential pathogen particles. Therefore, scientific operation of centralized air conditioning systems during the epidemic period has more advantages than disadvantages.

3.
EuropePMC; 2021.
Preprint in English | EuropePMC | ID: ppcovidwho-308253

ABSTRACT

Background: Many governments in East and Southeast Asia responded promptly and effectively at the onset of the COVID-19 pandemic. Systematically synthesizing these responses is vital for disease control evidence-based policy making.Methods: An extensive review of COVID-19 control measures was conducted in selected Asian countries and subregions, including Mainland China, Hong Kong, Taiwan, South Korea, Singapore, Japan, and Vietnam from January 1 to May 30, 2020. Control measures were categorized into administrative, public health, and health system measures. To evaluate the stringency and timeliness of responses, we developed two indices: the Initial Response Index (IRI) and the Modified Stringency Index (MSI), which builds on the Oxford COVID-19 Government Response Tracker (OxCGRT).Findings: Comprehensive administrative, public health, and health system control measures were implemented at the onset of the outbreak. Despite variations in package components, the stringency of control measures across the study sites increased with the acceleration of the outbreak, with public health control measures implemented the most stringently. Variations in daily average MSI scores are observed, with Mainland China scoring the highest (74·2), followed by Singapore (67·4), Vietnam (66·8), Hong Kong (66·2), South Korea (62·3), Taiwan (52·1), and Japan (50·3). Variations in IRI scores depicting timeliness were higher: Hong Kong, Taiwan, Vietnam, and Singapore acted faster (IRI>50·0), while Japan (42·4) and Mainland China (4·2) followed.Interpretation: Timely setting of stringency of the control measures, especially public health measures, at dynamically high levels is key to optimally controlling outbreaks.Funding: Saudi Ministry of Finance;Duke Global Health Institute.Declaration of Interests: The authors declare no conflict of interests.

4.
Applied Intelligence ; : 1-24, 2022.
Article in English | EuropePMC | ID: covidwho-1615233

ABSTRACT

Nonoverlapping sequential pattern mining, as a kind of repetitive sequential pattern mining with gap constraints, can find more valuable patterns. Traditional algorithms focused on finding all frequent patterns and found lots of redundant short patterns. However, it not only reduces the mining efficiency, but also increases the difficulty in obtaining the demand information. To reduce the frequent patterns and retain its expression ability, this paper focuses on the Nonoverlapping Maximal Sequential Pattern (NMSP) mining which refers to finding frequent patterns whose super-patterns are infrequent. In this paper, we propose an effective mining algorithm, Nettree for NMSP mining (NetNMSP), which has three key steps: calculating the support, generating the candidate patterns, and determining NMSPs. To efficiently calculate the support, NetNMSP employs the backtracking strategy to obtain a nonoverlapping occurrence from the leftmost leaf to its root with the leftmost parent node method in a Nettree. To reduce the candidate patterns, NetNMSP generates candidate patterns by the pattern join strategy. Furthermore, to determine NMSPs, NetNMSP adopts the screening method. Experiments on biological sequence datasets verify that not only does NetNMSP outperform the state-of-the-arts algorithms, but also NMSP mining has better compression performance than closed pattern mining. On sales datasets, we validate that our algorithm guarantees the best scalability on large scale datasets. Moreover, we mine NMSPs and frequent patterns in SARS-CoV-1, SARS-CoV-2 and MERS-CoV. The results show that the three viruses are similar in the short patterns but different in the long patterns. More importantly, NMSP mining is easier to find the differences between the virus sequences.

5.
Sustainability ; 13(22):12844, 2021.
Article in English | ProQuest Central | ID: covidwho-1538510

ABSTRACT

With vast potentials in improving operations and stimulating growth, digital transformation has aroused much attention from firms across the world. However, the high costs associated with the transformation can not be ignored. Limited research has looked into the organizational performance effects of digital transformation. After examining the benefits and costs of digital transformation, this research makes an empirical study on the impact of digital transformation on firm operational and financial performance. The panel data from 2010 to 2020 of 2254 manufacturing companies in China suggests that the intensity of digital transformation is in positive correlation with the process-based operating performance, and in the U-shaped correlation with the profit-oriented financial performance. Further, we find that digital transformation has a much more lasting impact on operating performance than on financial performance. The conditions required (i.e., policy and innovation environment) to improve the operating performance via digital transformation are more easing. This research shows the differentiated effect of digital transformation on different dimensions of organizational performance and provides guidance for companies to set the goals for digital transformation.

6.
iScience ; 24(12): 103426, 2021 Dec 17.
Article in English | MEDLINE | ID: covidwho-1509907

ABSTRACT

Glycosylation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein mediates viral entry and immune escape. While glycan site is determined by viral genetic code, glycosylation is completely dependent on host cell post-translational modification. Here, by producing SARS-CoV-2 virions from various host cell lines, viruses of different origins with diverse spike protein glycan patterns were revealed. Binding affinities to C-type lectin receptors (CLRs) DC&L-SIGN differed in the different glycan pattern virions. Although none of the CLRs supported viral productive infection, viral trans&cis-infection mediated by the CLRs were substantially changed among the different virions. Specifically, trans&cis-infection of virions with a high-mannose structure (Man5GlcNAc2) at the N1098 glycan site of the spike postfusion trimer were markedly enhanced. Considering L-SIGN co-expression with ACE2 on respiratory tract cells, our work underlines viral epigenetic glycosylation in authentic viral infection and highlights the attachment co-receptor role of DC&L-SIGN in SARS-CoV-2 infection and prevention.

9.
Eur J Med Chem ; 215: 113286, 2021 Apr 05.
Article in English | MEDLINE | ID: covidwho-1385487

ABSTRACT

Covalent drugs have been intensively studied in some very important fields such as anti-tumor and anti-virus, including the currently global-spread SARS-CoV-2. However, these drugs may interact with a variety of biological macromolecules and cause serious toxicology, so how to reactivate the inhibited targets seems to be imperative in the near future. Organophosphate was an extreme example, which could form a covalent bound easily with acetylcholinesterase and irreversibly inhibited the enzyme, causing high toxicology. Some nucleophilic oxime reactivators for organophosphate poisoned acetylcholinesterase had been developed, but the reactivation process was still less understanding. Herein, we proposed there should be a pre-reactivated pose during the reactivating process and compounds whose binding pose was easy to transfer to the pre-reactivated pose might be efficient reactivators. Then we refined the previous reactivators based on the molecular dynamic simulation results, the resulting compounds L7R3 and L7R5 were proven as much more efficient reactivators for organophosphate inhibited acetylcholinesterase than currently used oximes. This work might provide some insights for constructing reactivators of covalently inhibited targets by using computational methods.


Subject(s)
Acetylcholinesterase/chemistry , Cholinesterase Reactivators/chemistry , Acetylcholinesterase/metabolism , Cholinesterase Inhibitors/chemistry , Cholinesterase Reactivators/metabolism , Humans , Kinetics , Molecular Dynamics Simulation , Organophosphorus Compounds/chemistry , Proof of Concept Study , Protein Binding
10.
Environ Sci Pollut Res Int ; 28(40): 56376-56391, 2021 Oct.
Article in English | MEDLINE | ID: covidwho-1384555

ABSTRACT

It is important to know whether SARS-CoV-2 is spread through the air conditioning systems. Taking the central air conditioning system as an example, we analyze the mechanism and potential health risk of respiratory virus transmission in air-conditioned rooms and propose a method to study the risk of virus transmission in central air conditioning systems by investigating the data from medical experiments. The virus carrying capacity and the decay characteristics of indoor pathogen droplets are studied in this research. Additionally, the effects of air temperature and relative humidity on the virus survival in the air or on surfaces are investigated. The removal efficiency of infectious droplet nuclei by using an air conditioning filter was then determined. Thus, the transmission risk during the operation of the centralized air conditioning system is evaluated. The results show that the indoor temperature and humidity are controlled in the range of 20-25 °C and 40-70% by central air conditioning during the epidemic period, which not only benefits the health and comfort of residents, but also weakens the vitality of the virus. The larger the droplet size, the longer the viruses survive. Since the filter efficiency of the air conditioning filter increases with the increase in particle size, increasing the number of air changes of the circulating air volume can accelerate the removal of potential pathogen particles. Therefore, scientific operation of centralized air conditioning systems during the epidemic period has more advantages than disadvantages.


Subject(s)
Air Conditioning , Air Pollution, Indoor , COVID-19 , Viruses , Air Microbiology , Air Pollution, Indoor/analysis , COVID-19/transmission , Humans , Humidity , SARS-CoV-2 , Virus Diseases/transmission
11.
Mol Ther Methods Clin Dev ; 23: 108-118, 2021 Dec 10.
Article in English | MEDLINE | ID: covidwho-1379195

ABSTRACT

Because of the relatively limited understanding of coronavirus disease 2019 (COVID-19) pathogenesis, immunological analysis for vaccine development is needed. Mice and macaques were immunized with an inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine prepared by two inactivators. Various immunological indexes were tested, and viral challenges were performed on day 7 or 150 after booster immunization in monkeys. This inactivated SARS-CoV-2 vaccine was produced by sequential inactivation with formaldehyde followed by propiolactone. The various antibody responses and specific T cell responses to different viral antigens elicited in immunized animals were maintained for longer than 150 days. This comprehensive immune response could effectively protect vaccinated macaques by inhibiting viral replication in macaques and substantially alleviating immunopathological damage, and no clinical manifestation of immunopathogenicity was observed in immunized individuals during viral challenge. This candidate inactivated vaccine was identified as being effective against SARS-CoV-2 challenge in rhesus macaques.

12.
Int J Environ Res Public Health ; 18(16)2021 08 17.
Article in English | MEDLINE | ID: covidwho-1360753

ABSTRACT

AIM: Many governments in East and Southeast Asia responded promptly and effectively at the onset of the COVID-19 pandemic. Synthesizing and analyzing these responses is vital for disease control evidence-based policymaking. METHODS: An extensive review of COVID-19 control measures was conducted in selected Asian countries and subregions, including Mainland China, Hong Kong, Taiwan, South Korea, Singapore, Japan, and Vietnam from 1 January to 30 May 2020. Control measures were categorized into administrative, public health, and health system measures. To evaluate the stringency and timeliness of responses, we developed two indices: the Initial Response Index (IRI) and the Modified Stringency Index (MSI), which builds on the Oxford COVID-19 Government Response Tracker (OxCGRT). RESULTS: Comprehensive administrative, public health, and health system control measures were implemented at the onset of the outbreak. Despite variations in package components, the stringency of control measures across the study sites increased with the acceleration of the outbreak, with public health control measures implemented the most stringently. Variations in daily average MSI scores are observed, with Mainland China scoring the highest (74.2), followed by Singapore (67.4), Vietnam (66.8), Hong Kong (66.2), South Korea (62.3), Taiwan (52.1), and Japan (50.3). Variations in IRI scores depicting timeliness were higher: Hong Kong, Taiwan, Vietnam, and Singapore acted faster (IRI > 50.0), while Japan (42.4) and Mainland China (4.2) followed. CONCLUSIONS: Timely setting of stringency of the control measures, especially public health measures, at dynamically high levels is key to optimally controlling outbreaks.


Subject(s)
COVID-19 , Pandemics , Government , Hong Kong/epidemiology , Humans , SARS-CoV-2
13.
Gen Psychiatr ; 33(4): e100250, 2020.
Article in English | MEDLINE | ID: covidwho-1288444

ABSTRACT

BACKGROUND: During the outbreak of COVID-19, the national policy of home quarantine may affect the mental health of parents. However, few studies have investigated the mental health of parents during the COVID-19 pandemic. AIMS: To investigate the depression, anxiety and stress of the students' parents during the COVID-19 pandemic, and to explore the influence factors, especially the influence of social support and family-related factors. METHODS: The Generalised Anxiety Disorder-7, Patient Health Questionnaire-9, Perceived Stress Scale-10 and Social Support Rating Scale were applied to 1163 parents to measure the parents' depression, anxiety, stress and social support. RESULTS: (1) The detection rates of depression and anxiety in parents were 6.1% and 4.0%. The depression, anxiety and perceived stress of parents in central China were significantly higher than those in non-central China. The anxiety of college students' parents was lower than that of parents of the primary, middle and high school students. The depression, anxiety and perceived stress of parents with conflicts in the family were significantly higher than those with a harmonious family. Other factors that influence parents' depression, anxiety and perceived stress include marital satisfaction, social support, parents' history of mental illness and parenting style, etc. (2) The regression analysis results showed that perceived stress, social support, marital satisfaction, family conflicts, child's learning stage as well as parents' history of mental illness had significant effects on parents' anxiety and depression. CONCLUSION: During the COVID-19 pandemic, the mental health of parents was affected by a variety of factors. Good marital relationships, good social support, family harmony and parents without a history of mental illness may be protective factors for parents' mental health, while perceived stress and child in middle or high school are risk factors for parents' mental health.

14.
Emerg Microbes Infect ; 10(1): 1156-1168, 2021 Dec.
Article in English | MEDLINE | ID: covidwho-1249264

ABSTRACT

ABSTRACTThe risk of secondary infection with SARS-CoV-2 and influenza A virus is becoming a practical problem that must be addressed as the flu season merges with the COVID-19 pandemic. As SARS-CoV-2 and influenza A virus have been found in patients, understanding the in vivo characteristics of the secondary infection between these two viruses is a high priority. Here, hACE2 transgenic mice were challenged with the H1N1 virus at a nonlethal dose during the convalescent stage on 7 and 14 days post SARS-CoV-2 infection, and importantly, subsequent H1N1 infection showed enhanced viral shedding and virus tissue distribution. Histopathological observation revealed an extensive pathological change in the lungs related to H1N1 infection in mice recovered from SARS-CoV-2 infection, with severe inflammation infiltration and bronchiole disruption. Moreover, upon H1N1 exposure on 7 and 14 dpi of SARS-CoV-2 infection, the lymphocyte population activated at a lower level with T cell suppressed in both PBMC and lung. These findings will be valuable for evaluating antiviral therapeutics and vaccines as well as guiding public health work.


Subject(s)
Acute Lung Injury/pathology , Angiotensin-Converting Enzyme 2/genetics , COVID-19/pathology , Orthomyxoviridae Infections/pathology , Acute Lung Injury/virology , Animals , COVID-19/therapy , Coinfection/pathology , Coinfection/virology , Cytokines/blood , Disease Models, Animal , Female , Humans , Influenza A Virus, H1N1 Subtype/isolation & purification , Lung/pathology , Lymphocyte Count , Lymphocytes/immunology , Mice , Mice, Transgenic , Orthomyxoviridae Infections/therapy , SARS-CoV-2/isolation & purification , Viral Load , Virus Replication/physiology , Virus Shedding/physiology
15.
IEEE J Biomed Health Inform ; 25(5): 1347-1357, 2021 05.
Article in English | MEDLINE | ID: covidwho-1225649

ABSTRACT

The coronavirus disease 2019 (COVID-19) has swept all over the world. Due to the limited detection facilities, especially in developing countries, a large number of suspected cases can only receive common clinical diagnosis rather than more effective detections like Reverse Transcription Polymerase Chain Reaction (RT-PCR) tests or CT scans. This motivates us to develop a quick screening method via common clinical diagnosis results. However, the diagnostic items of different patients may vary greatly, and there is a huge variation in the dimension of the diagnosis data among different suspected patients, it is hard to process these indefinite dimension data via classical classification algorithms. To resolve this problem, we propose an Indefiniteness Elimination Network (IE-Net) to eliminate the influence of the varied dimensions and make predictions about the COVID-19 cases. The IE-Net is in an encoder-decoder framework fashion, and an indefiniteness elimination operation is proposed to transfer the indefinite dimension feature into a fixed dimension feature. Comprehensive experiments were conducted on the public available COVID-19 Clinical Spectrum dataset. Experimental results show that the proposed indefiniteness elimination operation greatly improves the classification performance, the IE-Net achieves 94.80% accuracy, 92.79% recall, 92.97% precision and 94.93% AUC for distinguishing COVID-19 cases from non-COVID-19 cases with only common clinical diagnose data. We further compared our methods with 3 classical classification algorithms: random forest, gradient boosting and multi-layer perceptron (MLP). To explore each clinical test item's specificity, we further analyzed the possible relationship between each clinical test item and COVID-19.


Subject(s)
COVID-19 Testing , COVID-19/diagnosis , Neural Networks, Computer , Algorithms , Area Under Curve , Databases, Factual , Humans , Reproducibility of Results , Time Factors
16.
Bioconjug Chem ; 32(5): 1034-1046, 2021 05 19.
Article in English | MEDLINE | ID: covidwho-1217668

ABSTRACT

SARS-CoV-2 caused the COVID-19 pandemic that lasted for more than a year. Globally, there is an urgent need to use safe and effective vaccines for immunization to achieve comprehensive protection against SARS-CoV-2 infection. Focusing on developing a rapid vaccine platform with significant immunogenicity as well as broad and high protection efficiency, we designed a SARS-CoV-2 spike protein receptor-binding domain (RBD) displayed on self-assembled ferritin nanoparticles. In a 293i cells eukaryotic expression system, this candidate vaccine was prepared and purified. After rhesus monkeys are immunized with 20 µg of RBD-ferritin nanoparticles three times, the vaccine can elicit specific humoral immunity and T cell immune response, and the neutralizing antibodies can cross-neutralize four SARS-CoV-2 strains from different sources. In the challenge protection test, after nasal infection with 2 × 105 CCID50 SARS-CoV-2 virus, compared with unimmunized control animals, virus replication in the vaccine-immunized rhesus monkeys was significantly inhibited, and respiratory pathology observations also showed only slight pathological damage. These analyses will benefit the immunization program of the RBD-ferritin nanoparticle vaccine in the clinical trial design and the platform construction to present a specific antigen domain in the self-assembling nanoparticle in a short time to harvest stable, safe, and effective vaccine candidates for new SARS-CoV-2 isolates.


Subject(s)
COVID-19 Vaccines/immunology , COVID-19/prevention & control , Nanoparticles/chemistry , Spike Glycoprotein, Coronavirus/metabolism , T-Lymphocytes/immunology , Animals , Antibodies, Neutralizing/immunology , Binding Sites , CD8-Positive T-Lymphocytes/immunology , COVID-19/immunology , Ferritins/chemistry , Ferritins/metabolism , Immunity, Humoral , Macaca mulatta , Male , Nanoparticles/metabolism , SARS-CoV-2/isolation & purification , SARS-CoV-2/physiology , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology , T-Lymphocytes/metabolism , Ultracentrifugation
17.
Environ Res ; 194: 110716, 2021 03.
Article in English | MEDLINE | ID: covidwho-1213219

ABSTRACT

The complex and changeable environment is a brand-new living condition for the viruses and pathogens released by the infected people to the indoor air or deposited on the surface of objects, which is an important external condition affecting the decay and transmission risk of the viruses. Exposure to contaminated surfaces is one of the main routes of respiratory diseases transmission. Therefore, it is very important for epidemic prevention and control to study the law of virus decay and the environmental coupling effect on various surfaces. Based on the analysis of the influencing mechanism, a large amount of experimental evidence on the survival of viruses on the surface of objects were excavated in this paper, and the effects of various factors, such as surface peripheral temperature, relative humidity, virus-containing droplet volume, surface materials and virus types, on the decay rate constants of viruses were comprehensively analyzed. It was found that although the experimental methods, virus types and experimental conditions varied widely in different experiments, the virus concentrations on the surface of objects all followed the exponential decay law, and the coupling effect of various factors was reflected in the decay rate constant k. Under different experimental conditions, k values ranged from 0.001 to 100 h-1, with a difference of 5 orders of magnitude, corresponding to the characteristic time t99 between 500 and 0.1 h when the virus concentration decreased by 99%. This indicates a large variation in the risk of virus transmission in different scenarios. By revealing the common law and individuality of the virus decay on the surface of objects, the essential relationship between the experimental observation phenomenon and virus decay was analyzed. This paper points out the huge difference in virus transmission risk on the surface at different time nodes, and discusses the prevention and control strategies to grasp the main contradictions in the different situations.


Subject(s)
Viruses , Climate , Humans , Humidity , Temperature
18.
Vaccine ; 39(20): 2746-2754, 2021 05 12.
Article in English | MEDLINE | ID: covidwho-1174522

ABSTRACT

BACKGROUND: This study examined the safety and immunogenicity of an inactivated SARS-CoV-2 vaccine. METHOD: In a phase I randomized, double-blinded, placebo-controlled trial involving 192 healthy adults 18-59 years old, two injections of three doses (50 EU, 100 EU, 150 EU) of an inactivated SARS-CoV-2 vaccine or placebo were administered intramuscularly at a 2- or 4-week interval. The safety and immunogenicity of the vaccine were evaluated. RESULTS: Vaccination was completed in 191 subjects. Forty-four adverse reactions occurred within 28 days, most commonly mild pain and redness at the injection site or slight fatigue. At days 14 and 28, the seroconversion rates were 87.5% and 79.2% (50 EU), 100% and 95.8% (100 EU), and 95.8% and 87.5% (150 EU), respectively, with geometric mean titers (GMTs) of 18.1 and 10.6, 54.5 and 15.4, and 37.1 and 18.5, respectively, for the schedules with 2-week and 4-week intervals. Seroconversion was associated with synchronous upregulation of antibodies against the S protein, N protein and virion and a cytotoxic T lymphocyte (CTL) response. No cytokines and immune cells related to immunopathology were observed. Transcriptome analysis revealed the genetic diversity of immune responses induced by the vaccine. INTERPRETATION: In a population aged 18-59 years in this trial, this inactivated SARS-CoV-2 vaccine was safe and immunogenic. TRIAL REGISTRATION: CTR20200943 and NCT04412538.


Subject(s)
COVID-19 Vaccines , COVID-19 , Vaccines , Adolescent , Adult , Antibodies, Viral , China , Double-Blind Method , Humans , Immunogenicity, Vaccine , Middle Aged , SARS-CoV-2 , Young Adult
19.
Epidemiol Infect ; 149: e24, 2021 01 14.
Article in English | MEDLINE | ID: covidwho-1065752

ABSTRACT

The severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) is highly contagious, and the coronavirus disease 2019 (COVID-19) pandemic caused by it has forced many countries to adopt 'lockdown' measures to prevent the spread of the epidemic through social isolation of citizens. Some countries proposed universal mask wearing as a protection measure of public health to strengthen national prevention efforts and to limit the wider spread of the epidemic. In order to reveal the epidemic prevention efficacy of masks, this paper systematically evaluates the experimental studies of various masks and filter materials, summarises the general characteristics of the filtration efficiency of isolation masks with particle size, and reveals the actual efficacy of masks by combining the volume distribution characteristics of human exhaled droplets with different particle sizes and the SARS-CoV-2 virus load of nasopharynx and throat swabs from patients. The existing measured data show that the filtration efficiency of all kinds of masks for large particles and extra-large droplets is close to 100%. From the perspective of filtering the total number of pathogens discharged in the environment and protecting vulnerable individuals from breathing live viruses, the mask has a higher protective effect. If considering the weighted average filtration efficiency with different particle sizes, the filtration efficiencies of the N95 mask and the ordinary mask are 99.4% and 98.5%, respectively. The mask can avoid releasing active viruses to the environment from the source of infection, thus maximising the protection of vulnerable individuals by reducing the probability of inhaling a virus. Therefore, if the whole society strictly implements the policy of publicly wearing masks, the risk of large-scale spread of the epidemic can be greatly reduced. Compared with the overall cost of social isolation, limited personal freedoms and forced suspension of economic activities, the inconvenience for citizens caused by wearing masks is perfectly acceptable.


Subject(s)
COVID-19/epidemiology , COVID-19/prevention & control , Masks/standards , Aerosols , COVID-19/transmission , Humans , Nasopharynx/virology , Oropharynx/virology , Particle Size , Viral Load
20.
Infect Dis Model ; 6: 324-342, 2021.
Article in English | MEDLINE | ID: covidwho-1030440

ABSTRACT

The coronavirus disease outbreak of 2019 (COVID-19) has been spreading rapidly to all corners of the word, in a very complex manner. A key research focus is in predicting the development trend of COVID-19 scientifically through mathematical modelling. We conducted a systematic review of epidemic prediction models of COVID-19 and the public health intervention strategies by searching the Web of Science database. 55 studies of the COVID-19 epidemic model were reviewed systematically. It was found that the COVID-19 epidemic models were different in the model type, acquisition method, hypothesis and distribution of key input parameters. Most studies used the gamma distribution to describe the key time period of COVID-19 infection, and some studies used the lognormal distribution, the Erlang distribution, and the Weibull distribution. The setting ranges of the incubation period, serial interval, infectious period and generation time were 4.9-7 days, 4.41-8.4 days, 2.3-10 days and 4.4-7.5 days, respectively, and more than half of the incubation periods were set to 5.1 or 5.2 days. Most models assumed that the latent period was consistent with the incubation period. Some models assumed that asymptomatic infections were infectious or pre-symptomatic transmission was possible, which overestimated the value of R0. For the prediction differences under different public health strategies, the most significant effect was in travel restrictions. There were different studies on the impact of contact tracking and social isolation, but it was considered that improving the quarantine rate and reporting rate, and the use of protective face mask were essential for epidemic prevention and control. The input epidemiological parameters of the prediction models had significant differences in the prediction of the severity of the epidemic spread. Therefore, prevention and control institutions should be cautious when formulating public health strategies by based on the prediction results of mathematical models.

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