scholarly journals Frequency of surveillance testing necessary to reduce transmission of the Delta variant of SARS-CoV-2

2021 ◽  
Author(s):  
Ahmed Elbanna ◽  
Nigel Goldenfeld
Keyword(s):  
Social Activity ◽  
Public University ◽  
Contact Tracing ◽  
Susceptible Population ◽  
Minimal Impact ◽  
Viral Loads ◽  
Viral Copy Number ◽  
Targeted Testing ◽  
Viral Copy ◽  
Additional Reduction

We estimate the reduction in transmission of SARS-CoV-2 achievable by surveillance testing of a susceptible population at different frequencies, comparing the cases of both the original Wuhan strain and the Delta variant. We estimate the viral dynamics using viral copy number at first detection combined with considerations arising from aerosol transmission. We take into account the recent findings that infected vaccinated adults may have live viral loads at the same level as infected unvaccinated adults. Our estimates suggest that twice weekly testing, which was adequate for the original strains of SARS-CoV-2 will be insufficient on its own to contain the spread of the Delta variant of concern. We exclude consideration of contact tracing since the rapidity of the onset of viral titre in the case of the Delta variant suggests that unless contact tracing and quarantine are performed very rapidly (ie. much less than a day), these mitigations will be of minimal impact in reducing transmission. These crude estimates do not take into account heterogeneity of susceptibility, social activity, and compliance, nor do they include the additional reduction in transmission that could be achieved by masking and social distancing. In the setting of a large public university, these considerations suggest that risk-targeted testing of vaccinated students, staff and faculty combined with surveillance testing of all unvaccinated individuals is the most efficient way to reduce transmission of COVID-19.

Infection with antiretroviral-susceptible HIV in an individual adherent to pre-exposure prophylaxis: strategies for treatment initiation

2021 ◽  
pp. 095646242097112
Author(s):  
Jessica M Hughes ◽  
Darrell HS Tan ◽  
Peter Anderson ◽  
Janani Bodhinayake ◽  
Paul A MacPherson
Keyword(s):  
Viral Load ◽  
Copy Number ◽  
Case Reports ◽  
Pharmacy Records ◽  
Treatment Regimens ◽  
Viral Copy Number ◽  
Low Copy Number ◽  
Viral Copy ◽  
Exposure Prophylaxis ◽  
Tenofovir Diphosphate

HIV pre-exposure prophylaxis (PrEP) is effective at preventing sexual acquisition of HIV, and failures in clinical trials are largely attributable to medication nonadherence. We report here a case of infection with a fully susceptible strain of HIV in an individual adherent to PrEP as demonstrated by pharmacy records and intracellular tenofovir diphosphate levels. At diagnosis, the viral load was 90 copies/mL precluding initial genotype testing due to low copy number. While PrEP failure is rare, this case underscores the importance of regular HIV testing for patient on PrEP and prompts discussion regarding the approach to treatment following failure where an initial genotype is not yet available or not possible due to low viral load. Few other case reports of PrEP failure exist in the literature and approaches to treatment varied widely. We suggest the initial viral copy number may guide next steps and discuss the risks and benefits of stopping PrEP, escalating therapy with integrase inhibitors or boosted protease inhibitors, or switching to non-nucleoside antiretroviral treatment regimens.

scholarly journals Pathogenicity of novel goose-origin astrovirus causing gout in goslings

2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Dan Yin ◽  
Jiajun Tian ◽  
Jing Yang ◽  
Yi Tang ◽  
Youxiang Diao
Keyword(s):  
Biochemical Parameters ◽  
Clinical Symptoms ◽  
Future Research ◽  
Tissue Tropism ◽  
Virus Shedding ◽  
Viral Loads ◽  
Blood Biochemical ◽  
Copy Numbers ◽  
Viral Copy ◽  
Kidney Liver

Abstract Background A novel goose-origin astrovirus (GoAstV) has broken out across China in recent years, causing gout in goslings with a mortality rate of around 50%. However, our understanding of the dynamic distribution, tissue tropism and pathogenesis of GoAstV is incomplete. In order to assess its pathogenicity, one-day-old goslings were inoculated separately with GoAstV via oral and subcutaneous injection routes. Results Clinical symptoms, gross and microscopic lesions, blood biochemical parameters and viral loads were detected and recorded for 20 days after infection. Typical gout was observed in experimental goslings. GoAstV can be replicated in tissues and cause pathological damage, especially in the kidney, liver, heart and spleen. Virus-specific genomic RNA was detected in blood, cloacal swabs and all representative tissues, and virus shedding was detected up to 20 days after inoculation, suggesting that GoAstV has a wide tissue tropism and spread systematically after inoculation. The viral copy numbers examined in kidney were the highest, followed by spleen and liver. Conclusion This experiment determined the accurate value of viral loads and biochemical indicators of GoAstV-induced goslings. These findings increase our understanding of the pathogenicity of GoAstV in goslings and provide more reference for future research.

Activation-Induced CD4+ T Cell Death in HIV-Positive Individuals Correlates with Fas Susceptibility, CD4+ T Cell Count, and HIV Plasma Viral Copy Number

1999 ◽  
Vol 15 (17) ◽  
pp. 1509-1518 ◽  
Author(s):  
D. H. Dockrell ◽  
A. D. Badley ◽  
A. Algeciras-Schimnich ◽  
M. Simpson ◽  
R. Schut ◽  
...  
Keyword(s):  
Cell Death ◽  
T Cell ◽  
Cell Count ◽  
Copy Number ◽  
Cd4 T Cell ◽  
Hiv Positive ◽  
Viral Copy Number ◽  
Viral Copy ◽  
Cd4 T Cell Count

scholarly journals Quantification of SARS-CoV-2 viral copy number in saliva mouthwash samples using digital droplet PCR

2020 ◽  
Author(s):  
Lisa Oberding ◽  
Jia Hu ◽  
Byron Berenger ◽  
Abu Naser Mohon ◽  
Dylan R. Pillai
Keyword(s):  
Viral Load ◽  
Copy Number ◽  
Clinical Samples ◽  
Digital Droplet Pcr ◽  
Viral Copy Number ◽  
Droplet Pcr ◽  
Precise Quantification ◽  
Viral Copy ◽  
Mouth Wash

AbstractSaliva samples were collected through a simple mouth wash procedure and viral load quantified using a technology called digital droplet PCR. Data suggest ddPCR allows for precise quantification of viral load in clinical samples infected with SARS-CoV-2.

scholarly journals Bacteriophage self-counting in the presence of viral replication

2021 ◽  
Vol 118 (51) ◽  
pp. e2104163118
Author(s):  
Tianyou Yao ◽  
Seth Coleman ◽  
Thu Vu Phuc Nguyen ◽  
Ido Golding ◽  
Oleg A. Igoshin
Keyword(s):  
Gene Expression ◽  
Viral Replication ◽  
Viral Gene Expression ◽  
Host Cells ◽  
Optimal Decision ◽  
Viral Gene ◽  
Viral Genomes ◽  
Viral Copy Number ◽  
Viral Copy ◽  
Type Phage

When host cells are in low abundance, temperate bacteriophages opt for dormant (lysogenic) infection. Phage lambda implements this strategy by increasing the frequency of lysogeny at higher multiplicity of infection (MOI). However, it remains unclear how the phage reliably counts infecting viral genomes even as their intracellular number increases because of replication. By combining theoretical modeling with single-cell measurements of viral copy number and gene expression, we find that instead of hindering lambda’s decision, replication facilitates it. In a nonreplicating mutant, viral gene expression simply scales with MOI rather than diverging into lytic (virulent) and lysogenic trajectories. A similar pattern is followed during early infection by wild-type phage. However, later in the infection, the modulation of viral replication by the decision genes amplifies the initially modest gene expression differences into divergent trajectories. Replication thus ensures the optimal decision—lysis upon single-phage infection and lysogeny at higher MOI.

Colorimetric loop-mediated isothermal amplification (LAMP) for cost-effective and quantitative detection of SARS-CoV-2: the change in color in LAMP-based assays quantitatively correlates with viral copy number

2021 ◽  
Author(s):  
Everardo González-González ◽  
Itzel Montserrat Lara-Mayorga ◽  
Iram Pablo Rodríguez-Sánchez ◽  
Yu Shrike Zhang ◽  
Sergio O. Martínez-Chapa ◽  
...  
Keyword(s):  
Copy Number ◽  
Quantitative Method ◽  
Diagnostic Performance ◽  
Cost Effective ◽  
Isothermal Amplification ◽  
Quantitative Detection ◽  
Loop Mediated Isothermal Amplification ◽  
Viral Copy Number ◽  
Viral Copy

Colorimetric LAMP for COVID-19 intensified diagnostics: a simple and quantitative method comparable in diagnostic performance to RT-qPCR.

scholarly journals SARS-CoV-2 transmission and control in a hospital setting: an individual-based modelling study

2020 ◽  
Author(s):  
Qimin Huang ◽  
Anirban Mondal ◽  
Xiaobing Jiang ◽  
Mary Ann Horn ◽  
Fei Fan ◽  
...  
Keyword(s):  
Healthcare Workers ◽  
Hospital Setting ◽  
Credible Interval ◽  
Contact Tracing ◽  
Global Public Health ◽  
Minimal Impact ◽  
Social Distancing ◽  
Work Related ◽  
The Impact ◽  
Outbreak Size

Background: Development of strategies for mitigating the severity of COVID-19 is now a top global public health priority. We sought to assess strategies for mitigating the COVID-19 outbreak in a hospital setting via the use of non-pharmaceutical interventions such as social distancing, self-isolation, tracing and quarantine, wearing facial masks/ personal protective equipment. Methods: We developed an individual-based model for COVID-19 transmission among healthcare workers in a hospital setting. We calibrated the model using data of a COVID-19 outbreak in a hospital unit in Wuhan in a Bayesian framework. The calibrated model was used to simulate different intervention scenarios and estimate the impact of different interventions on outbreak size and workday loss. Results: We estimated that work-related stress increases susceptibility to COVID-19 infection among healthcare workers by 52% (90% Credible Interval (CrI): 16.4% - 93.0%). The use of high efficacy facial masks was shown to be able to reduce infection cases and workday loss by 80% (90% CrI: 73.1% - 85.7%) and 87% (CrI: 80.0% - 92.5%), respectively. The use of social distancing alone, through reduced contacts between healthcare workers, had a marginal impact on the outbreak. A strict quarantine policy with the isolation of symptomatic cases and a high fraction of pre-symptomatic/ asymptomatic cases (via contact tracing or high test rate), could only prolong outbreak duration with minimal impact on the outbreak size. Our results indicated that a quarantine policy should be coupled with other interventions to achieve its effect. The effectiveness of all these interventions was shown to increase with their early implementation. Conclusions: Our analysis shows that a COVID-19 outbreak in a hospital's non-COVID-19 unit can be controlled or mitigated by the use of existing non-pharmaceutical measures.

scholarly journals Interplay between mobility, multi-seeding and lockdowns shapes COVID-19 local impact

2021 ◽  
Vol 17 (10) ◽  
pp. e1009326
Author(s):  
Mattia Mazzoli ◽  
Emanuele Pepe ◽  
David Mateo ◽  
Ciro Cattuto ◽  
Laetitia Gauvin ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Local Level ◽  
Nonlinear Effects ◽  
Contact Tracing ◽  
Peak Time ◽  
Susceptible Population ◽  
Incidence And Mortality ◽  
Infected Area ◽  
Local Impact ◽  
The Impact

Assessing the impact of mobility on epidemic spreading is of crucial importance for understanding the effect of policies like mass quarantines and selective re-openings. While many factors affect disease incidence at a local level, making it more or less homogeneous with respect to other areas, the importance of multi-seeding has often been overlooked. Multi-seeding occurs when several independent (non-clustered) infected individuals arrive at a susceptible population. This can lead to independent outbreaks that spark from distinct areas of the local contact (social) network. Such mechanism has the potential to boost incidence, making control efforts and contact tracing less effective. Here, through a modeling approach we show that the effect produced by the number of initial infections is non-linear on the incidence peak and peak time. When case importations are carried by mobility from an already infected area, this effect is further enhanced by the local demography and underlying mixing patterns: the impact of every seed is larger in smaller populations. Finally, both in the model simulations and the analysis, we show that a multi-seeding effect combined with mobility restrictions can explain the observed spatial heterogeneities in the first wave of COVID-19 incidence and mortality in five European countries. Our results allow us for identifying what we have called epidemic epicenter: an area that shapes incidence and mortality peaks in the entire country. The present work further clarifies the nonlinear effects that mobility can have on the evolution of an epidemic and highlight their relevance for epidemic control.

scholarly journals Effect of lyophilization on infectivity and viral load of Adenovirus

2015 ◽  
Vol 3 (1) ◽  
pp. 15-21
Author(s):  
Bimlesh Kumar Jha ◽  
Birendra Prasad Gupta ◽  
Prashanna Maharjan ◽  
Somila Kakshapati ◽  
Nabin Narayan Munankarmi
Keyword(s):  
Viral Load ◽  
Copy Number ◽  
Virus Stock ◽  
Log Reduction ◽  
Viral Copy Number ◽  
Significant Difference ◽  
Viral Copy ◽  
Viral Load Assay ◽  
Temperature And Pressure ◽  
And Storage

Freeze drying (Lyophilization) performed at temperature and pressure below the triple point is being practiced for the preservation of virus stocks for longer periods. The present study is aimed to lyophilize adenovirus strain to study its effects on infectivity and viral load. In-house adenovirus reference strain (stock virus) was propagated in Hep-2 cell line in 25cm2 cell culture flasks. In 24-well plates the serial dilutions of stock virus from 10-1 to 10-7 (100μl inoculum) was inoculated in each well with Hep-2 cells for TCID50 titer and viral DNA was extracted separately to determine viral load by Taqman Real Time PCR. Stock virus was lyophilized in 3 lots and stored at RT (25±2°C) and 4°C separately for 1, 4 and 6 months and subjected to TCID50 (for viral infectivity) and viral load assay (for total viral genome copies). Following lyophilisation and storage of adenoviral strains at RT and 4°C separately did not affect significantly on the viral stability, infectivity as well as viral copy number till 4 months. However, storage at RT for 6 months resulted in 1 log reduction in viral copy number. Thus, storage of even lyophilized virus stock would necessitate a temperature of at least 4°C for prolonged periods. The present study could successfully lyophilize adenovirus and retain its infectivity over a period of 6 months when stored at RT and 4°C. No significant difference in the infectivity or TCID50 titer was observed in the lyophilized virus as compared to the stock virus. However, the viral load was observed to increase with lyophilization of the virus over 6 months when stored at 4°C which possibly is due to the concentration of the virus on freeze-drying.Nepal Journal of Biotechnology. Dec. 2015 Vol. 3, No. 1: 15-21

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