scholarly journals Increased Transmissibility of SARS-CoV-2 Lineage B.1.1.7 by Age and Viral Load: Evidence from Danish Households

2021 ◽  
Author(s):  
Frederik Plesner Lyngse ◽  
Kåre Mølbak ◽  
Robert Leo Skov ◽  
Lasse Engbo Christiansen ◽  
Laust Hvas Mortensen ◽  
...  
Keyword(s):  
Viral Load ◽  
Neutralizing Antibodies ◽  
Decision Makers ◽  
Rt Pcr ◽  
Primary Case ◽  
Important Public Health ◽  
Household Transmission ◽  
Multiplicative Effect ◽  
New Knowledge ◽  
Pharmaceutical Interventions

Aim The aim of this study was to estimate the household transmissibility of SARSCoV-2 for lineage B.1.1.7 compared with other lineages, by age and viral load. Furthermore, we wanted to estimate whether there is a multiplicative or additive effect of the increased transmissibility of B.1.1.7 compared with other lineages. Background New lineages of SARS-CoV-2 are of potential concern due to higher transmissibility, risk of severe outcomes, and/or escape from neutralizing antibodies. Lineage B.1.1.7 has been estimated to be more transmissible than other previously known lineages, but the association between transmissibility and risk factors, such as age of primary case and viral load is still unknown. Methods We used comprehensive administrative data from Denmark, comprising the full population, all SARS-CoV-2 RT-PCR tests, and all WGS lineage data (January 11 to February 7, 2021), to estimate household transmissibility stratified by lineage B.1.1.7 and other lineages. Results We included 5,241 households with primary cases; 808 were infected with SARS-CoV-2 lineage B.1.1.7 and 4,433 were infected with other lineages. The attack rate was 38% in households with a primary case infected with B.1.1.7 and 27% in households with a primary case infected with other lineages. Primary cases infected with B.1.1.7 had an increased transmissibility of 1.5-1.7 times that of primary cases infected with other lineages. The increased transmissibility of B.1.1.7 was multiplicative across age and viral load. Conclusions The results found in this study add new knowledge that can be used to mitigate the further spread of SARS-CoV-2 lineage B.1.1.7, which is becoming increasingly widespread in numerous countries. Our results clarify that the transmissibility of B.1.1.7 should be included as a multiplicative effect in mathematical models used as a tool for decision makers. The results may have important public health implications, as household transmission may serve as a bridge between otherwise separate transmission domains, such as schools and physical workplaces, despite implemented non-pharmaceutical interventions.

scholarly journals Increased transmissibility of SARS-CoV-2 lineage B.1.1.7 by age and viral load

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Frederik Plesner Lyngse ◽  
Kåre Mølbak ◽  
Robert Leo Skov ◽  
Lasse Engbo Christiansen ◽  
Laust Hvas Mortensen ◽  
...  
Keyword(s):  
Risk Factors ◽  
Viral Load ◽  
Administrative Data ◽  
Attack Rate ◽  
Neutralizing Antibodies ◽  
Primary Case ◽  
Alpha Variant ◽  
Full Population

AbstractNew lineages of SARS-CoV-2 are of potential concern due to higher transmissibility, risk of severe outcomes, and/or escape from neutralizing antibodies. Lineage B.1.1.7 (the Alpha variant) became dominant in early 2021, but the association between transmissibility and risk factors, such as age of primary case and viral load remains poorly understood. Here, we used comprehensive administrative data from Denmark, comprising the full population (January 11 to February 7, 2021), to estimate household transmissibility. This study included 5,241 households with primary cases; 808 were infected with lineage B.1.1.7 and 4,433 with other lineages. Here, we report an attack rate of 38% in households with a primary case infected with B.1.1.7 and 27% in households with other lineages. Primary cases infected with B.1.1.7 had an increased transmissibility of 1.5–1.7 times that of primary cases infected with other lineages. The increased transmissibility of B.1.1.7 was multiplicative across age and viral load.

scholarly journals Household Transmission of SARS-CoV-2: A Prospective Longitudinal Study Showing Higher Viral Load and Increased Transmissibility of the Alpha Variant Compared to Previous Strains

2021 ◽  
Vol 9 (11) ◽  
pp. 2371
Author(s):  
Cathinka Halle Julin ◽  
Anna Hayman Robertson ◽  
Olav Hungnes ◽  
Gro Tunheim ◽  
Terese Bekkevold ◽  
...  
Keyword(s):  
Viral Load ◽  
Longitudinal Study ◽  
Digital Pcr ◽  
Primary Case ◽  
Prospective Longitudinal Study ◽  
Viral Loads ◽  
Household Contacts ◽  
Household Transmission ◽  
Alpha Variant ◽  
Prospective Longitudinal

We studied the secondary attack rate (SAR), risk factors, and precautionary practices of household transmission in a prospective, longitudinal study. We further compared transmission between the Alpha (B.1.1.7) variant and non-Variant of Concern (non-VOC) viruses. From May 2020 throughout April 2021, we recruited 70 confirmed COVID-19 cases with 146 household contacts. Participants donated biological samples eight times over 6 weeks and answered questionnaires. SARS-CoV-2 infection was detected by real-time RT-PCR. Whole genome sequencing and droplet digital PCR were used to establish virus variant and viral load. SARS-CoV-2 transmission occurred in 60% of the households, and the overall SAR for household contacts was 50%. The SAR was significantly higher for the Alpha variant (78%) compared with non-VOC viruses (43%) and was associated with a higher viral load. SAR was higher in household contacts aged ≥40 years (69%) than in younger contacts (40–47%), and for contacts of primary cases with loss of taste/smell. Children had lower viral loads and were more often asymptomatic than adults. Sleeping separately from the primary case reduced the risk of transmission. In conclusion, we found substantial household transmission, particularly for the Alpha variant. Precautionary practices seem to reduce SAR, but preventing household transmission may become difficult with more contagious variants, depending on vaccine use and effectiveness.

scholarly journals Delta variant and mRNA Covid-19 vaccines effectiveness: higher odds of vaccine infection breakthroughs

2021 ◽  
Author(s):  
Irina Kislaya ◽  
Eduardo Freire Rodrigues ◽  
Vitor Borges ◽  
Joao Paulo Gomes ◽  
Carlos Sousa ◽  
...  
Keyword(s):  
Viral Load ◽  
Conditional Logistic Regression ◽  
Secondary Analysis ◽  
Vaccination Status ◽  
Decision Makers ◽  
Control Measures ◽  
Rt Pcr ◽  
Gene Target ◽  
Alpha Variant ◽  
Roll Out

Background: The SARS-CoV-2 Delta variant (B.1.617.2), initially identified in India, has become predominant in several countries, including Portugal. Few studies have compared the effectiveness of mRNA vaccines against Delta versus Alpha variant of concern (VOC) and estimated variant-specific viral loads in vaccine infection breakthroughs cases. In the context of Delta dominance, this information is critical to inform decision-makers regarding the planning of restrictions and vaccination roll-out. Methods: We developed a case-case study to compare mRNA vaccines' effectiveness against Delta (B.1.617.2) versus Alpha (B.1.1.7) variants. We used RT-PCR positive cases notified to the National Surveillance System between 17th of May and 4th of July 2021 (week 20 to 26) and information about demographics and vaccination status through the electronic vaccination register. Whole-genome sequencing (WGS) or spike (S) gene target failure (SGTF) data were used to classify SARS-CoV-2 variants. The odds of vaccinated individuals to become infected (odds of vaccine infection breakthrough) in Delta cases compared to Alpha SARS-CoV-2 cases was estimated by conditional logistic regression adjusted for age group, sex, and matched by the week of diagnosis. As a surrogate of viral load, mean RT-PCR Ct values were stratified and compared between vaccine status and VOC. Results: Of the 2 097 SARS-CoV-2 RT-PCR positive cases included in the analysis, 966 (46.1%) were classified with WGS and 1131 (53.9%) with SGTF. Individuals infected with the Delta variant were more frequently vaccinated 162 (12%) than individuals infected with the Alpha variant 38 (5%). We report a statistically significant higher odds of vaccine infection breakthrough for partial (OR=1.70; CI95% 1.18 to 2.47) and complete vaccination (OR=1.96; CI95% 1.22 to 3.14) in the Delta cases when compared to the Alpha cases, suggesting lower mRNA vaccine effectiveness against Delta cases. On our secondary analysis, we observed lower mean Ct values for the Delta VOC cases versus Alpha, regardless the vaccination status. Additionally, the Delta variant cases revealed a Ct-value mean increase of 2.24 (CI95% 0.85 to 3.64) between unvaccinated and fully vaccinated breakthrough cases contrasting with 4.49 (CI95% 2.07 to 6.91) in the Alpha VOC, suggesting a lower impact of vaccine on viral load of Delta cases. Conclusions: We found significantly higher odds of vaccine infection breakthrough in Delta cases when compared to Alpha cases, suggesting lower effectiveness of the mRNA vaccines in preventing infection with the Delta variant. Additionally, the vaccine breakthrough cases are estimated to be of higher mean Ct values, suggesting higher infectiousness with the Delta variant infection. These findings can help decision-makers weigh on the application or lifting of control measures and adjusting vaccine roll-out depending on the predominance of the Delta variant and the coverage of partial and complete mRNA vaccination.

scholarly journals Association between SARS-CoV-2 Transmission Risk, Viral Load, and Age: A Nationwide Study in Danish Households

2021 ◽  
Author(s):  
Frederik Plesner Lyngse ◽  
Kåre Mølbak ◽  
Kristina Træholt Franck ◽  
Claus Nielsen ◽  
Robert Leo Skov ◽  
...  
Keyword(s):  
Viral Load ◽  
Strong Association ◽  
Transmission Risk ◽  
Global Public Health ◽  
Rt Pcr ◽  
Nationwide Study ◽  
Ct Value ◽  
Household Transmission ◽  
Value Association ◽  
Full Population

Aim The objective of this observational study was to investigate the association between SARS-CoV-2 transmission risk, RT-PCR Cycle threshold (Ct) values, and age of infected cases in Danish households. Background The Covid-19 pandemic is one of the most serious global public health threats in recent times. Understanding transmission of SARS-CoV-2 is of utmost importance to be able to respond to outbreaks and take action against the spread of the disease. Viral load is generally thought to correlate with transmission risk. Methods We used comprehensive administrative register data from Denmark, comprising the full population and all SARS-CoV-2 tests (August 25, 2020 to February 10, 2021), to estimate household transmission risk. Results We found that the transmission risk was negatively associated—approximately linear—with the Ct values of the tested primary cases. Also, we found that even for relatively high Ct values, the risk of transmission was not negligible; e.g., for primary cases with a Ct value of 38, we found a transmission risk of 8%. This implies that there is no obvious cut-off for Ct values for risk of transmission. We estimated the transmission risk according to age and found an almost linearly increasing transmission risk with the age of the primary cases for adults (≥20 years) and negatively for children (<20 years). Age had a higher impact than Ct value on the risk of transmission. Conclusions Lower Ct values (indicating higher viral load) are associated with higher risk of SARS-CoV-2 transmission. However, even at high Ct values, transmission occurs. In addition, we found a strong association between age and transmission risk, and this dominated the Ct value association.

scholarly journals SARS-CoV-2 Infections and Viral Isolations among Serially Tested Cats and Dogs in Households with Infected Owners in Texas, USA

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 938
Author(s):  
Sarah A. Hamer ◽  
Alex Pauvolid-Corrêa ◽  
Italo B. Zecca ◽  
Edward Davila ◽  
Lisa D. Auckland ◽  
...  
Keyword(s):  
Neutralizing Antibodies ◽  
Case Definition ◽  
Initial Test ◽  
Rt Pcr ◽  
Genome Sequences ◽  
Infected People ◽  
Household Transmission ◽  
Transmission Study ◽  
Initial Sampling

Understanding the ecological and epidemiological roles of pets in the transmission of SARS-CoV-2 is critical for animal and human health, identifying household reservoirs, and predicting the potential enzootic maintenance of the virus. We conducted a longitudinal household transmission study of 76 dogs and cats living with at least one SARS-CoV-2-infected human in Texas and found that 17 pets from 25.6% of 39 households met the national case definition for SARS-CoV-2 infections in animals. This includes three out of seventeen (17.6%) cats and one out of fifty-nine (1.7%) dogs that were positive by RT-PCR and sequencing, with the virus successfully isolated from the respiratory swabs of one cat and one dog. Whole-genome sequences of SARS-CoV-2 obtained from all four PCR-positive animals were unique variants grouping with genomes circulating among people with COVID-19 in Texas. Re-sampling showed persistence of viral RNA for at least 25 d-post initial test. Additionally, seven out of sixteen (43.8%) cats and seven out of fifty-nine (11.9%) dogs harbored SARS-CoV-2 neutralizing antibodies upon initial sampling, with relatively stable or increasing titers over the 2–3 months of follow-up and no evidence of seroreversion. The majority (82.4%) of infected pets were asymptomatic. ‘Reverse zoonotic’ transmission of SARS-CoV-2 from infected people to animals may occur more frequently than recognized.

scholarly journals Viral Dynamics and Real-Time RT-PCR Ct Values Correlation with Disease Severity in COVID-19

Diagnostics ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 1091
Author(s):  
Ali A. Rabaan ◽  
Raghavendra Tirupathi ◽  
Anupam A Sule ◽  
Jehad Aldali ◽  
Abbas Al Mutair ◽  
...  
Keyword(s):  
Viral Load ◽  
Real Time ◽  
Disease Severity ◽  
False Negative ◽  
Influential Factors ◽  
Confirmatory Test ◽  
Acid Extraction ◽  
Rt Pcr ◽  
Viral Kinetics ◽  
Ct Value

Real-time RT-PCR is considered the gold standard confirmatory test for coronavirus disease 2019 (COVID-19). However, many scientists disagree, and it is essential to understand that several factors and variables can cause a false-negative test. In this context, cycle threshold (Ct) values are being utilized to diagnose or predict SARS-CoV-2 infection. This practice has a significant clinical utility as Ct values can be correlated with the viral load. In addition, Ct values have a strong correlation with multiple haematological and biochemical markers. However, it is essential to consider that Ct values might be affected by pre-analytic, analytic, and post-analytical variables such as collection technique, specimen type, sampling time, viral kinetics, transport and storage conditions, nucleic acid extraction, viral RNA load, primer designing, real-time PCR efficiency, and Ct value determination method. Therefore, understanding the interpretation of Ct values and other influential factors could play a crucial role in interpreting viral load and disease severity. In several clinical studies consisting of small or large sample sizes, several discrepancies exist regarding a significant positive correlation between the Ct value and disease severity in COVID-19. In this context, a revised review of the literature has been conducted to fill the knowledge gaps regarding the correlations between Ct values and severity/fatality rates of patients with COVID-19. Various databases such as PubMed, Science Direct, Medline, Scopus, and Google Scholar were searched up to April 2021 by using keywords including “RT-PCR or viral load”, “SARS-CoV-2 and RT-PCR”, “Ct value and viral load”, “Ct value or COVID-19”. Research articles were extracted and selected independently by the authors and included in the present review based on their relevance to the study. The current narrative review explores the correlation of Ct values with mortality, disease progression, severity, and infectivity. We also discuss the factors that can affect these values, such as collection technique, type of swab, sampling method, etc.

scholarly journals Performance of Self-Collected Saliva Testing Compared with Nasopharyngeal Swab Testing for the Detection of SARS-CoV-2

Viruses ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 895
Author(s):  
Florence Carrouel ◽  
Martine Valette ◽  
Hervé Perrier ◽  
Maude Bouscambert-Duchamp ◽  
Claude Dussart ◽  
...  
Keyword(s):  
Viral Load ◽  
Quantitative Pcr ◽  
Statistical Analyses ◽  
Fair Agreement ◽  
Quantitative Detection ◽  
Nasopharyngeal Swab ◽  
Rt Pcr ◽  
Noninvasive Techniques ◽  
Concordance Probability ◽  
Salivary Test

The aim of this study was to determine whether self-collected pure saliva (SCPS) is comparable to nasopharyngeal (NP) swabs in the quantitative detection of SARS-CoV-2 by RT-PCR in asymptomatic, mild patients with confirmed COVID-19. Thirty-one patients aged from 18 to 85 years were included between 9 June and 11 December 2020. A SCPS sample and a NP sample were taken for each patient. Quantitative PCR was performed to detect SARS-CoV-2 viral load. Results of SCPS vs NP samples testing were compared. Statistical analyses were performed. Viral load was significantly correlated (r = 0.72). The concordance probability was estimated at 73.3%. In symptomatic adults, SCPS performance was similar to that of NP swabs (Percent Agreement = 74.1%; p = 0.11). Thus, the salivary test based on pure oral saliva samples easily obtained by noninvasive techniques has a fair agreement with the nasopharyngeal one in asymptomatic, mild patients with a confirmed diagnosis of COVID-19.

scholarly journals Household transmission and incidence of positive SARS-CoV-2 RT-PCR in symptomatic healthcare workers, clinical course and outcome: a French hospital experience

2020 ◽  
pp. oemed-2020-106866
Author(s):  
Evguenia Krastinova ◽  
Valérie Garrait ◽  
Marie-Thérèse Lecam ◽  
André Coste ◽  
Emmanuelle Varon ◽  
...  
Keyword(s):  
Healthcare Workers ◽  
Current Smoker ◽  
Infection Rates ◽  
Rt Pcr ◽  
Living Situation ◽  
Household Transmission ◽  
Occupational Profile ◽  
Household Members ◽  
French Hospital ◽  
At Home

ObjectivesAlthough healthcare workers (HCWs) have been particularly affected by SARS-CoV-2, detailed data remain scarce. In this study, we investigated infection rates, clinical characteristics, occupational exposure and household transmission among all symptomatic HCWs screened by SARS-CoV-2 RT-PCR between 17 March (French lockdown) and 20 April.MethodsSARS-CoV-2 RT-PCR was proposed to symptomatic (new cough or dyspnoea) HCWs at Creteil Hospital in one of the Parisian suburbs most severely affected by COVID-19. Data on occupational profile, living situation and household, together with self–isolation and mask use at home were collected, as well as the number of cases in the household.ResultsThe incidence rate of symptomatic SARS-CoV-2 was estimated to be 5% (110/2188). A total of 110 (35%) of the 314 HCWs tested positive and 9 (8%) were hospitalised. On multivariate analysis, factors independently associated with positive RT-PCR were occupational profile with direct patient facing (OR 3.1, 95% CI 1.1 to 8.8), p<0.03), and presence of anosmia (OR 5.7, 95% CI 3.1 to 10.6), p<0.0001). Being a current smoker was associated with negative RT-PCR (OR 0.3, 95% CI 0.1 to 0.7), p=0.005). Transmission from HCWs to household members was reported in 9 (14%) cases, and 2 deaths occurred. Overall, self-isolation was possible in 52% of cases, but only 31% of HCWs were able to wear a mask at home.ConclusionThis is the first study to report infection rates among HCWs during the peak of the SARS-CoV-2 epidemic in France and the lockdown period, highlighting the risk related to occupational profile and household transmission.

scholarly journals Automated Low Cost Method of Quantification of Hepatitis C Virus

2015 ◽  
Vol 14 (3) ◽  
pp. 247-253
Author(s):  
Faiz MMT Marikar ◽  
Dammika Senevirathna ◽  
Neil Fernandopulle
Keyword(s):  
Viral Load ◽  
Hepatitis C ◽  
Blood Donors ◽  
Low Cost ◽  
Medical Science ◽  
Simultaneous Detection ◽  
Plasma Samples ◽  
Rt Pcr ◽  
Viral Genomes ◽  
Post Therapy

This paper describes the development of a Dig-dUTP based multiplex real time RT-PCR for the simultaneous detection of HCV viral amount in plasma samples. Viral genomes were identified in the same sample by Dig-dUTP PCR 216 bp region. Analysis of known scalar concentrations of reference plasma indicated that the multiplex procedure detects at least 500 copies/ml of HCV. In addition, we also assayed HCV viral load in eighty co-infected patients and in fifteen blood donors, confirming the sensitivity and specificity of the assay. This method may represent a useful alternative method for the detection of HCV co-infection, reliable for a rapid and relatively inexpensive screening of blood donors. The assay may be used to determine post-therapy viral clearance.Bangladesh Journal of Medical Science Vol.14(3) 2015 p.247-253

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