We consider an epidemic model with nonlocal diffusion and free boundaries, which describes the evolution of an infectious agents with nonlocal diffusion and the infected humans without diffusion, ...where humans get infected by the agents, and infected humans in return contribute to the growth of the agents. The model can be viewed as a nonlocal version of the free boundary model studied by Ahn, Beak and Lin 2, with its origin tracing back to Capasso et al. 5,6. We prove that the problem has a unique solution defined for all t>0, and its long-time dynamical behaviour is governed by a spreading-vanishing dichotomy. Sharp criteria for spreading and vanishing are also obtained, which reveal significant differences from the local diffusion model in 2. Depending on the choice of the kernel function in the nonlocal diffusion operator, it is expected that the nonlocal model here may have accelerated spreading, which would contrast sharply to the model of 2, where the spreading has finite speed whenever spreading happens 33.
Porcine epidemic diarrhea virus (PEDV) causes high mortality in neonatal piglets. The PEDV spike (S) protein contains two intracellular sorting motifs, YxxΦ (tyrosine-based motif YEVF or YEAF) and ...KVHVQ at the cytoplasmic tail, yet their functions have not been fully elucidated. Some Vero cell-adapted and/or attenuated PEDV variants contain ablations in these two motifs. We hypothesized that these motifs contribute to viral pathogenicity. By transiently expressing PEDV S proteins with mutations in the motifs, we confirmed that the motif KVHVQ is involved in retention of the S proteins in the endoplasmic reticulum (ER)-Golgi intermediate compartment (ERGIC). In addition, we showed that the YxxΦ motif triggers endocytosis of S proteins. These two motifs synergistically regulate the level of S expressed on the cell surface. To investigate their role in viral pathogenicity, we generated three recombinant PEDVs by introducing deletions or a mutation in the two motifs of the infectious clone of PEDV PC22A strain (icPC22A): (i) icΔ10aa (ΔYxxΦEKVHVQ), (ii) icΔ5aa (ΔKVHVQ), and (iii) icYA (Y1378A, to an inactivated motif, AEVF). Infection of Vero cells with icΔ10aa resulted in larger syncytia and more virions, with reduced numbers of S protein projections on the surface compared with icPC22A. Furthermore, we orally inoculated five groups of 5-day-old gnotobiotic piglets with the three mutants, icPC22A, or a mock treatment. Mutant icΔ10aa caused less severe diarrhea rate and significantly milder intestinal lesions than icPC22A, icΔ5aa, and icYA. These data suggest that the deletion of both motifs can reduce the virulence of PEDV in piglets.
Many coronaviruses (CoVs) possess conserved motifs YxxΦ and/or KxHxx/KKxx in the cytoplasmic tail of the S protein. The KxHxx/KKxx motif has been identified as the ER retrieval signal, but the function of the YxxΦ motif in the intracellular sorting of CoV S proteins remains controversial. In this study, we showed that the YxxΦ of PEDV S protein is an endocytosis signal. Furthermore, using reverse genetics technology, we evaluated its role in PEDV pathogenicity in neonatal piglets. Our results explain one attenuation mechanism of Vero cell-adapted PEDV variants lacking functional YxxΦ and KVHVQ motifs. Knowledge from this study may aid in the design of efficacious live attenuated vaccines against PEDV, as well as other CoVs bearing the same motif in their S protein.
Epidemics on multilayer simplicial complexes Fan, Junfeng; Yin, Qian; Xia, Chengyi ...
Proceedings of the Royal Society. A, Mathematical, physical, and engineering sciences,
05/2022, Volume:
478, Issue:
2261
Journal Article
Peer reviewed
Simplicial complexes describe the simple fact that in social networks a link can connect more than two individuals. As we show here, this has far-reaching consequences for epidemic spreading, in ...particular in the context of a multilayer network model, where one layer is a virtual social network and the other one is a physical contact network. The social network layer is responsible for the transmission of information via pairwise or higher order 2-simplex interactions among individuals, while the physical layer is responsible for the epidemic spreading. We use the microscopic Markov chain approach to derive the probability transition equations and to determine epidemic outbreak thresholds. We further support these results with Monte Carlo simulations, which are in good agreement, thus confirming the analytical tractability of the proposed model. We find that information transmission rates are frequently low when actual disease transmission rates in the physical network are low or medium, and we show that this can be mitigated effectively by introducing 2-simplex interactions in the social network. The relative ease of introducing higher-order interactions in virtual social networks means that this could be exploited to inhibit epidemic outbreaks.
Porcine epidemic diarrhea (PED) caused by PED virus (PEDV) remains a big threat to the swine industry worldwide. Vaccination with live attenuated vaccine is a promising method to prevent and control ...PED, because it can elicit a more protective immunity than the killed vaccine, subunit vaccine, and so on. In this study, we found two obvious deletions in the genome of a high passage of AH2012/12. We further confirmed the second deletion which contains seven amino acids at the carboxy-terminus of the S2 gene and the start codon of ORF3 can reduce its pathogenicity
. Animal experiments indicated that the recombinant PEDV with deleted carboxy-terminus of S gene showed higher IgG, IgA, neutralization antibodies, and protection effects against virus challenge than the killed vaccine. These data reveal that the engineering of the carboxy-terminus of the S2 gene may be a promising method to develop live attenuated vaccine candidates of PEDV.
•The experiences of pregnant women from past epidemics and pandemics were consolidated.•Midwives’ and nurses’ perceptions of epidemics and pandemics were explored.•Individualized and contextualized ...educational support is needed.•Culturally congruent care and emotional and financial support need to be prioritized.•Healthcare professionals can consider technology-based and community-led supportive programs.
To consolidate qualitative research studies that examined the experiences and needs of pregnant women, midwives, and nurses of maternity units to provide a way forward for future research and practices during the current pandemic and future epidemics and pandemics.
Qualitative systematic review and meta-synthesis.
Four electronic databases—PubMed, Scopus, PsycINFO, and Cumulative Index to Nursing and Allied Health (CINAHL).
Qualitative studies with samples of pregnant women, midwives, and/or nurses of maternity units who experienced epidemics and/or pandemics were searched from 1 January 2000 to 4 April 2020. The included studies were critically appraised using the ten-item Critical Appraisal Skills Programme (CASP) tool.
Eight studies were included in this review. Four themes emerged from the synthesis: (1) psychological responses, (2) challenges faced, (3) coping strategies, and (4) sources of support and support needs.
Pregnant women, midwives, and nurses experienced negative psychological responses during epidemics and pandemics. Challenges, such as limited available information and public stigma, were faced. Various coping strategies, such as actively looking for more information and seeking solace in religions, were practiced by pregnant women, midwives, and nurses. Families were both sources of support and stress and they expressed needs for more informational, emotional, and financial support during pandemics.
More culturally diverse research in the future that includes the development of technology-based programs, trained community volunteer-led programs, psychosocial interventions, and anti-stigma and awareness initiatives are needed to combat the current pandemic and future public health crises.
Modeling local coronavirus outbreaks Chang, Joseph T.; Kaplan, Edward H.
European journal of operational research,
01/2023, Volume:
304, Issue:
1
Journal Article
Peer reviewed
Open access
•A probabilistic approach to modeling local coronavirus outbreaks is presented.•The model generalizes the well-known SIR and SEIR models.•The model enables new insights regarding the timing and ...meaning of herd immunity.•The model enables parameter estimation from observed lagged indicators of infection.•The model extends naturally to testing- and isolation-based interventions.
This article presents an overview of methods developed for the modeling and control of local coronavirus outbreaks. The article reviews early transmission dynamics featuring exponential growth in infections, and links this to a renewal epidemic model where the current incidence of infection depends upon the expected value of incidence randomly lagged into the past. This leads directly to simple formulas for the fraction of the population infected in an unmitigated outbreak, and reveals herd immunity as the solution to an optimization problem. The model also leads to direct and easy-to-understand formulas for aligning observable epidemic indicators such as cases, hospitalizations and deaths with the unobservable incidence of infection, and as a byproduct leads to a simple first-order approach for estimating the effective reproduction number Rt. The model also leads naturally to direct assessments of the effectiveness of isolation in preventing the spread of infection. This is illustrated with application to repeat asymptomatic screening programs of the sort utilized by universities, sports teams and businesses to prevent the spread of infection.
Severe acute respiratory syndrome coronavirus (SARS-CoV), emerged from China and rapidly spread worldwide. Over 8098 people fell ill and 774 died before the epidemic ended in July 2003. Bats are ...likely an important reservoir for SARS-CoV. SARS-like CoVs have been detected in horseshoe bats and civet cats. The main mode of transmission of SARS-CoV is through inhalation of respiratory droplets. Faeco-oral transmission has been recorded. Strict infection control procedures with respiratory and contact precautions are essential. Fever and respiratory symptoms predominate, and diarrhea is common. Treatment involves supportive care. There are no specific antiviral treatments or vaccines available.
•Cell attenuated porcine epidemic diarrhea virus strain Zhejiang08 provides effective immune protection in piglets.•Zhejiang08 has higher ability to stimulate DCs and activates T-cell proliferation ...than classical vaccine strain CV777.•Potential glycosylation site lacking in S protein may cause the stronger immune response.
Since 2010, the porcine epidemic diarrhea coronavirus (PEDV) has caused significant damage to the global pork industry. However, classical PEDV vaccine strains only provide limited protection against emerging strains. In this study, we successfully isolated and attenuated the PEDV epidemic strain Zhejiang08, which was characterized by good cell adaptation and high-titer production 48 h post infection in Vero E6 cells. The attenuated virus induced a high level of virus-specific neutralizing antibodies until 120 days after immunization in piglets and provided complete protection when challenged with an emerging virus strain on day 14 post immunization. Moreover, the capability to activate dendritic cells (DCs) of this isolate was identified. Higher expression levels of IL-12 and IFN-γ were recorded in DCs after treatment with Zhejiang08 for 24 h. Furthermore, genome sequencing and phylogenetic analysis revealed high homology between the main antigen epitopes of Zhejiang08 and PEDV pandemic isolates following 2011. Combining the glycosylation site prediction results and their distribution within the spatial structure of the S protein, led to the conclusion that the observed more effective host immune response of Zhejiang08 compared to CV777 was possibly associated with a lack of the potential glycosylation site in the 296 amino acids of the S protein. In summary, we illustrated that the attenuated virus represents a promising vaccine candidate.
SIS Epidemic Propagation on Hypergraphs Bodó, Ágnes; Katona, Gyula Y.; Simon, Péter L.
Bulletin of mathematical biology,
04/2016, Volume:
78, Issue:
4
Journal Article
Peer reviewed
Open access
Mathematical modelling of epidemic propagation on networks is extended to hypergraphs in order to account for both the community structure and the nonlinear dependence of the infection pressure on ...the number of infected neighbours. The exact master equations of the propagation process are derived for an arbitrary hypergraph given by its incidence matrix. Based on these, moment closure approximation and mean-field models are introduced and compared to individual-based stochastic simulations. The simulation algorithm, developed for networks, is extended to hypergraphs. The effects of hypergraph structure and the model parameters are investigated via individual-based simulation results.
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