scholarly journals Multiple Outbreaks Resulting from Asymptomatic Infection in Spreading of COVID-19

2021 ◽  
Author(s):  
Jun Li ◽  
Mingju Ma
Keyword(s):  
Hopf Bifurcation ◽  
Compartmental Model ◽  
Biological Significance ◽  
Asymptomatic Infection ◽  
Infected People ◽  
Infected Population ◽  
Multiple Contacts ◽  
Subcritical Hopf Bifurcation ◽  
Asymptomatic Infections ◽  
The Difference

Abstract In this paper, we establish a compartmental model for the transmission of COVID-19 with both symptomatic and asymptomatic infections. The difference is that in our model, we consider the infection caused by multiple contacts with asymptomatic infected population. Through the dynamic analysis of the model, we found that when there is only one contact with an asymptomatic infected people, the system has a unique threshold to control the disease. When there is two contact with asymptomatic infected population, the system will undergo forward bifurcation, backward bifurcation, saddle-node bifurcation, supercritical Hopf bifurcation, subcritical Hopf bifurcation, and Bogdanov-Takens bifurcation with codimension 2. Finally, we give The complete bifurcation diagram and global phase diagram of the system, and the biological significance of our results are also given.

scholarly journals Epidemiological characteristics and the effectiveness of countermeasures to control coronavirus disease 2019 in Ningbo City, China

2020 ◽  
Author(s):  
Xuying Lao ◽  
Li Luo ◽  
Zhao Lei ◽  
Ting Fang ◽  
Yi Chen ◽  
...  
Keyword(s):  
Attack Rate ◽  
Asymptomatic Infection ◽  
Assessment Data ◽  
Exact Test ◽  
Imported Cases ◽  
Asymptomatic Infections ◽  
The Difference ◽  
Novel Coronavirus ◽  
Epidemiological Characteristics ◽  
High Disease Burden

Abstract Background: A novel coronavirus (SARS-CoV-2) has spread widely and led to high disease burden around the world. This study aimed to explore key parameters of SARS-CoV-2 infection and to assess the effectiveness of interventions to control the coronavirus disease 2019 (COVID-19).Methods: A susceptible – exposed – infectious – asymptomatic – recovered (SEIAR) model was developed for the assessment. Data of symptomatic and asymptomatic infection of SARS-CoV-2 were collected to calculate the key parameters of the model in Ningbo City, China.Results: A total of 157 confirmed COVID-19 cases (including 51 imported cases and 106 secondary cases) and 30 asymptomatic infections were reported in Ningbo City. The proportion of asymptomatic has an increasing trend. The proportion of asymptomatic of elder people was lower than younger people, and the difference was statistical significant (Fisher’s Exact Test, P = 0.034). There were 22 clusters associated with 167 SARS-CoV-2 infections, among which 29 cases were asymptomatic, with a proportion of 17.37%. We found that the secondary attack rate of asymptomatic was almost the same as that of symptomatic cases, and no significance was observed (χ2 = 1.350, P = 0.245) by Kruskal-Wallis test. The effective reproduction number (Reff) was 1.43 which revealed that the transmissibility of SARS-CoV-2 was moderate. If the interventions were not strengthened, the duration of the outbreak would last about 16 months with a simulated attack rate of 44.15%. The total attack rate and duration of the outbreak would increase along with the increasing delay of intervention.Conclusions: SARS-CoV-2 had moderate transmissibility in Ningbo City, China. Asymptomatic infection has the same transmissibility as symptomatic. The integrated interventions were implemented at different stages during the outbreak, which found to be exceedingly effective in China.

scholarly journals Characterization of Salmonella serotypes prevalent in asymptomatic people and patients

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Haiyan Xu ◽  
Weibing Zhang ◽  
Kai Zhang ◽  
Yue Zhang ◽  
Zhenyu Wang ◽  
...  
Keyword(s):  
Antimicrobial Resistance ◽  
Asymptomatic Infection ◽  
Resistance Rate ◽  
Human Infection ◽  
The Other ◽  
Resistance Testing ◽  
Multi Drug Resistance ◽  
Discriminative Ability ◽  
Source Of Infection ◽  
The Difference

Abstract Background Infection with Salmonella enterica usually results in diarrhea, fever, and abdominal cramps, but some people become asymptomatic or chronic carrier as a source of infection for others. This study aimed to analyze the difference in serotype, antimicrobial resistance, and genetic profiles between Salmonella strains isolated from patients and those from asymptomatic people in Nantong city, China. Methods A total of 88 Salmonella strains were collected from patients and asymptomatic people from 2017 to 2018. Serotyping, antimicrobial susceptibility testing, and PFGE analysis were performed to analyze the characteristics of these strains. Results Twenty serotypes belonging to 8 serogroups were identified in the 88 Salmonella strains. S. Typhimurium remained to be the predominant serotype in strains from both patients and asymptomatic people. Among the 27 strains from patients, S. Enteritidis and S. Rissen were shown as the other two major serotypes, while S. London, S. Derby, and S. Meleagridis were demonstrated as the other significant serotypes among the 61 strains from asymptomatic people. Antimicrobial resistance testing revealed that 84.1% of strains from both resources were multi-drug resistant. PFGE displayed a highly discriminative ability to differentiate strains belonging to S. Derby, S. Typhimurium, etc., but could not efficiently differentiate serotypes like S. Enteritidis. Conclusions This study’s results demonstrated that S. Typhimurium could cause human infection in both symptomatic and asymptomatic state; S. London, S. Derby, and S. Meleagridis usually cause asymptomatic infection, while S. Enteritidis infection mainly results in human diseases. The high multi-drug resistance rate detected in the antimicrobial resistance and diverse PFGE profiles of these strains implied that the strains were isolated from different sources, and the increased surveillance of Salmonella from both patients and asymptomatic people should be taken to control the disease.

scholarly journals Human Astrovirus Outbreak in a Daycare Center and Propagation among Household Contacts

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1100
Author(s):  
Ignacio Parrón ◽  
Elsa Plasencia ◽  
Thais Cornejo-Sánchez ◽  
Mireia Jané ◽  
Cristina Pérez ◽  
...  
Keyword(s):  
Acute Gastroenteritis ◽  
Age Groups ◽  
Rt Pcr ◽  
Daycare Center ◽  
Infected People ◽  
Conditioning Factors ◽  
Household Contacts ◽  
Human Astrovirus ◽  
Asymptomatic Infections ◽  
Clinical Cases

We investigated an outbreak of acute gastroenteritis due to human astrovirus in a daycare center, describing the transmission mechanism, the most affected age groups, conditioning factors and the extent of the outbreak among household contacts of the daycare center attenders. Data were collected from persons exposed at the daycare center and their home contacts. Fecal samples from affected and non-affected daycare center attenders were analyzed for viruses causing acute gastroenteritis by RT-PCR. The percentage of households affected and the attack rates (AR) were calculated. The attack rates were compared using the rate ratio (RR) with 95% confidence intervals. Information was obtained from 245 people (76 attenders and 169 contacts) of whom 49 were clinical cases. Five HAstV-4, two HAstV-8 and three non-typable HAstV cases were identified (six from clinical cases and four from asymptomatic infected people). The global AR was 20% (41.2% in children aged < 2 years). Data were obtained from 67 households: 20 households of affected attenders and 47 of non-affected attendees. Household contacts of affected attenders had a higher AR (74.3%) than that of non-affected attendees (2.4%). We found asymptomatic infections amongst daycare attendees. The transmission of HAstV during the outbreak was not limited to the daycare center but extended to household contacts of both affected and non-affected attenders.

Subcritical Hopf bifurcation in NeNd hollow cathode discharge

1994 ◽  
Vol 196 (3-4) ◽  
pp. 191-194 ◽  
Author(s):  
P.R. Sasi Kumar ◽  
V.P.N. Nampoori ◽  
C.P.G. Vallabhan
Keyword(s):  
Hopf Bifurcation ◽  
Hollow Cathode ◽  
Hollow Cathode Discharge ◽  
Subcritical Hopf Bifurcation

Nonlinear Vibration Analysis of a Flexible Rotor Supported by a Flexure Pivot Tilting Pad Journal Bearing in Comparison to a Fixed Profile Journal Bearing with Experimental Verification

2021 ◽  
Author(s):  
Nuntaphong Koondilogpiboon ◽  
Tsuyoshi Inoue
Keyword(s):  
Hopf Bifurcation ◽  
Journal Bearing ◽  
Flexible Rotor ◽  
Maximum Test ◽  
Operating Region ◽  
Stable Operating ◽  
Subcritical Hopf Bifurcation ◽  
Tilting Pad ◽  
Calculation Results ◽  
Tilting Pad Journal Bearing

Abstract In this paper, an efficient numerical method consisting of the real mode component mode synthesis (CMS) model reduction, shooting method with parallel computing, and Floquet analysis was developed for nonlinear rotordynamics analysis of a flexible rotor supported by a 4-lobe flexure pivot tilting pad journal bearing (FPTPJB) in load-on-pad (LOP) and load-between-pad (LBP) orientations in comparison to a fixed profile journal bearing (JB) of the same pad geometry. The method used the rotor's finite elements and bearing forces obtained from directly solving the Reynolds equation to determine the limit cycles and Hopf bifurcation types. For the investigated rotor and bearing parameters, the numerical results indicated that the onset speed of instability (OSI) of FPTPJB is considerably higher than that of JB of the same orientation. Also, FPTPJB in LOP orientation yielded higher OSI than the LBP one, whereas the OSI of JB in LOP orientation was substantially higher than the LBP counterpart. Nonlinear calculation results indicated that all bearing types and orientations gave subcritical Hopf bifurcation. The FPTPJB in LOP orientation produced the largest stable operating region, whereas the JB in LBP configuration yield the smallest one. The experiment showed subcritical Hopf bifurcation occurred at speed close to the calculated OSI in all cases except FPTPJB in LOP orientation that the OSI is higher than the maximum test rig speed. The whirling orbit had the same frequency as the first critical speed and precessed in the direction of shaft rotation.

Association Between the CDC6 G1321A Polymorphism and the Risk of Cervical Cancer

2010 ◽  
Vol 20 (5) ◽  
pp. 856-861 ◽  
Author(s):  
Xing-Dong Xiong ◽  
Li-Qin Zeng ◽  
Qing-Yuan Xiong ◽  
Sheng-Xiang Lu ◽  
Zhi-Zhen Zhang ◽  
...  
Keyword(s):  
Cervical Cancer ◽  
Cell Proliferation ◽  
Statistical Significance ◽  
Biological Significance ◽  
Brdu Incorporation ◽  
General Validity ◽  
Cervical Cancer Risk ◽  
Healthy Female ◽  
The Difference ◽  
Incorporation Assay

Introduction:Cell division cycle protein 6 (CDC6) plays critical roles in DNA replication and carcinogenesis. The biological significance of the CDC6 G1321A polymorphism (V441I, rs13706) on cervical carcinogenesis is still unknown. Here, we examined the potential influence of this polymorphism on cell proliferation and the individual's susceptibility to cervical cancer.Methods:We genotyped the CDC6 G1321A polymorphism in 87 cervical cancer cases and 110 healthy female subjects. Unconditional logistic regression analysis was used to estimate the association between the genotypes and the risk of cervical cancer. The BrdU incorporation assay was applied to analyze the effect of this polymorphism on cell proliferation.Results:Compared with the GG homozygotes, the cervical cancer risk was significantly reduced in the individuals with the heterozygous AG genotype (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.28-0.98; P = 0.042) or the homozygous AA genotype (OR, 0.29; 95% CI, 0.09-0.89; P = 0.030). Further stratified analyses showed that the decreased risk of cervical cancer was more evident among younger subjects (≤44 years old) with the AG or AA genotypes (OR, 0.44; 95% CI, 0.21-0.92; P = 0.029 and OR, 0.12; 95% CI, 0.03-0.61; P = 0.010, respectively). The BrdU incorporation assay showed that 293T cells transfected with CDC6-441I (1321A) had a lower proliferation rate in comparison with those transfected with CDC6-441V (1321G), although the difference did not reach statistical significance at the 0.05 level.Conclusions:The CDC6 G1321A polymorphism may contribute to the risk of cervical cancer. Further studies with more subjects and in diverse ethnic populations are necessary to confirm the general validity of our findings.

scholarly journals The Effectiveness Of High Levels Of Knowledge Regarding Hiv/Aids In Reducing Discriminatory Attitudes And Behaviour Towards Hiv-Infected People

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
M. Pirie ◽  
W. J. Coetsee
Keyword(s):  
Sample Size ◽  
Primary Objective ◽  
Large Sample Size ◽  
Infected People ◽  
Eta Squared ◽  
Secondary Objective ◽  
Level Of Knowledge ◽  
The Difference ◽  
F Statistics ◽  
Hiv Aids

The primary objective of this study was to assess whether there is a relationship between increasing levels of knowledge about HIV/AIDS and perceptions of discriminatory attitudes and behaviour towards people with HIV/AIDS. Employees (3662) from a large accounting firm were exposed to a survey and a response rate of 41% or 1532 was received. The secondary objective of the study was to determine whether there were any statistically significant differences in the mean difference of knowledge scores of groups created in terms of the different biographical variables. ANOVA’S (to determine the significance of differences between the means), t-tests (two groups only) and F-statistics were used for the analysis. Given the large sample size an F-test is not conclusive and the effect of the difference in sample size needs to be taken into account. For this reason it was also necessary to look at the Partial Eta Squared. Results indicate that respondents are generally knowledgeable about the prevention and transmission of HIV/AIDS and that respondents’ level of knowledge correlates negatively with discriminatory practices.

scholarly journals Modelling HIV dynamics with cell-to-cell transmission and CTL response

2021 ◽  
Author(s):  
Zirui Zhu ◽  
Ranchao Wu ◽  
Yu Yang ◽  
Yancong Xu
Keyword(s):  
Hopf Bifurcation ◽  
Cell Interaction ◽  
Backward Bifurcation ◽  
Hiv Treatment ◽  
Hiv Model ◽  
Ctl Response ◽  
Hiv Dynamics ◽  
Subcritical Hopf Bifurcation ◽  
Cell Transmission ◽  
New Type

In most HIV models, the emergence of backward bifurcation means that the control for basic reproduction number less than one is no longer effective for HIV treatment. In this paper, we study an HIV model with CTL response and cell-to-cell transmission by using the dynamical approach. The local and global stability of equilibria is investigated, the relations of subcritical Hopf bifurcation and supercritical bifurcation points are revealed, especially, the so-called new type bifurcation is also found with two Hopf bifurcation curves meeting at the same Bogdanov-Takens bifurcation point. Forward and backward bifurcation, Hopf bifurcation, saddle-node bifurcation, Bogdanov-Takens bifurcation are investigated analytically and numerically. Two limit cycles are also found numerically, which indicates that the complex behavior of HIV dynamics. Interestingly, the role of cell-to-cell interaction is fully uncovered, it may cause the oscillations to disappear and keep the so-called new type bifurcation persist. Finally, some conclusions and discussions are also given.

scholarly journals APLIKASI MODEL EPIDEMIK SEIAR-SEI PADA PENYEBARAN PENYAKIT MALARIA DENGAN INFEKSI ASIMTOMATIK DAN SUPER INFEKSI

2018 ◽  
Vol 15 (2) ◽  
pp. 67
Author(s):  
Stella Maryana Belwawin
Keyword(s):  
Equilibrium Point ◽  
Basic Reproduction Number ◽  
Reproduction Number ◽  
Asymptomatic Infection ◽  
Endemic Equilibrium ◽  
Asymptomatic Infections ◽  
The Stability ◽  
Super Infection ◽  
The Basic Reproduction Number

AbstractThis aim of this study is to determine the point of equilibrium and analyze the stability of SEIAR-SEI model on malaria disease with asymptomatic infection, super infection and the effect of the mosquito's life cycle. This study also aim is to measure the sensitivity of the spread of malaria to the parameters of asymptomatic infections, the rate of treatment, and the rate of birth of mosquitoes through the magnitude of . The method in this research is deductively, through several stage, such as  determination of disease-free equilibrium point and endemic equilibrium point, determination of basic reproduction number (), analyze of the basic reproduction number sensitivity of the spread of malaria to the parameters of asymptomatic infections, the rate of treatment, and the rate of birth of mosquitoes. The endemic equilibrium point was obtained using rule of Descartes. The result show that the change in the value of parameter , , and  has effect on the basic reproduction number (). Treatment factors in the human population influence the elimination of malaria in a population. Whereas asymptomatic infection factors and the birth rate of adult mosquitoes influence the increase in malaria infection. Keywords:  Malaria, asymptomatic infection, super infection, basic reproduction number, rule of descrates. AbstrakPenelitian ini bertujuan menentukan titik keseimbangan dan menganalisis kestabilan dari model SEIAR_SEI pada penyakit malaria dengan pengaruh infeksi asimtomatik, super infeksi, dan siklus hidup nyamuk. Penelitian ini juga bertujuan mengukur tingkat sensitivitas penyebaran penyakit malaria terhadap parameter infeksi asimtomatik, laju pengobatan, serta laju kelahiran nyamuk.melalu besaran .  Metode yang digunakan dalam penelitian ini adalah metode deduktif dengan langkah-langkah : menentukan titik keseimbangan bebas penyakit dan endemik dan menentukan bilangan reproduksi dasar ). Analisis sensitivitas bilangan reproduksi dasar dilakukan terhadap parameter infeksi asimtomatik, pengobatan, dan laju kelahiran nyamuk. Tititk keseimbangan endemik diperoleh dengan aturan descrates. Hasil yang diperoleh menunjukkan parameter , , dan  berpengaruh terhadap bilangan reproduksi dasar (). Faktor pengobatan berpengaruh terhadap eliminasi penyakit malaria. Sedangkan faktor infeksi asimtomatik dan laju kelahiran nyamuk dewasa berpengaruh terhadap peningkatan infeksi penyakit malaria. Kata kunci: Malaria, Infeksi Asimtomatik, Super Infeksi, Bilangan Reproduksi Dasar, Aturan Descrates . 

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