SARS-CoV-2 diagnostic testing rates determine the sensitivity of genomic surveillance programs

Cost-effectiveness of SARS-CoV-2 self-testing at routine gatherings to minimize community-level infections in lower-middle income countries: A mathematical modeling study

Places of worship serve as a venue for both mass and routine gathering around the world, and therefore are associated with risk of large-scale SARS-CoV-2 transmission. However, such routine gatherings also offer an opportunity to distribute self-tests to members of the community to potentially help mitigate transmission and reduce broader community spread of SARS-CoV-2. Over the past four years, self-testing strategies have been an impactful tool for countries' response to the COVID-19 pandemic, especially early on to mitigate the spread when vaccination and treatment options were limited. We used an agent-based mathematical model to estimate the impact of various strategies of symptomatic and asymptomatic self-testing for a fixed percentage of weekly routine gatherings at places of worship on community transmission of SARS-CoV-2 in Brazil, Georgia, and Zambia. Testing strategies assessed included weekly and bi-weekly self-testing across varying levels of vaccine effectiveness, vaccine coverage, and reproductive numbers to simulate developing stages of the COVID-19 pandemic. Self-testing symptomatic people attending routine gatherings can cost-effectively reduce the spread of SARS-CoV-2 within places of worship and the community, resulting in incremental cost-effectiveness ratios of $69-$303 USD. This trend is especially true in contexts where population level attendance at such gatherings is high, demonstrating that a distribution approach is more impactful when a greater proportion of the population is reached. Asymptomatic self-testing of attendees at 100% of places of worship in a country results in the greatest percent of infections averted and is consistently cost-effective but remains costly. Budgetary needs for asymptomatic testing are expensive and likely unaffordable for lower-middle income countries (520-1550x greater than that of symptomatic testing alone), promoting that strategies to strengthen symptomatic testing should remain a higher priority.

Surveillance strategies for the detection of new pathogen variants across epidemiological contexts

Surveillance systems that monitor pathogen genome sequences are critical for rapidly detecting the introduction and emergence of pathogen variants. To evaluate how interactions between surveillance capacity, variant properties, and the epidemiological context influence the timeliness of pathogen variant detection, we developed a geographically explicit stochastic compartmental model to simulate the transmission of a novel SARS-CoV-2 variant in New York City. We measured the impact of (1) testing and sequencing volume, (2) geographic targeting of testing, (3) the timing and location of variant emergence, and (4) the relative variant transmissibility on detection speed and on the undetected disease burden. Improvements in detection times and reduction of undetected infections were driven primarily by increases in the number of sequenced samples. The relative transmissibility of the new variant and the epidemic context of variant emergence also influenced detection times, showing that individual surveillance strategies can result in a wide range of detection outcomes, depending on the underlying dynamics of the circulating variants. These findings help contextualize the design, interpretation, and trade-offs of genomic surveillance strategies of pandemic respiratory pathogens.

Risk of COVID-19 in Children throughout the Pandemic and the Role of Vaccination: A Narrative Review

At the beginning of the coronavirus disease 2019 (COVID-19) pandemic, persons ≥65 years of age and healthcare personnel represented the most vulnerable groups with respect to risk of infection, severe illness, and death. However, as the pandemic progressed, there was an increasingly detrimental effect on young children and adolescents. Severe disease and hospitalization increased over time in pediatric populations, and containment measures created substantial psychosocial, educational, and economic challenges for young people. Vaccination of children against COVID-19 has been shown to reduce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and severe outcomes in pediatric populations and may also help to prevent the spread of variants of concern and improve community immunity. This review discusses the burden of COVID-19 on children throughout the pandemic, the role of children in disease transmission, and the impact of COVID-19 vaccination.

Drivers and impact of the early silent invasion of SARS-CoV-2 Alpha

SARS-CoV-2 variants of concern (VOCs) circulated cryptically before being identified as a threat, delaying interventions. Here we studied the drivers of such silent spread and its epidemic impact to inform future response planning. We focused on Alpha spread out of the UK. We integrated spatio-temporal records of international mobility, local epidemic growth and genomic surveillance into a Bayesian framework to reconstruct the first three months after Alpha emergence. We found that silent circulation lasted from days to months and decreased with the logarithm of sequencing coverage. Social restrictions in some countries likely delayed the establishment of local transmission, mitigating the negative consequences of late detection. Revisiting the initial spread of Alpha supports local mitigation at the destination in case of emerging events.

Impact and cost-effectiveness of SARS-CoV-2 self-testing strategies in schools: a multicountry modelling analysis

OBJECTIVES

To determine the most epidemiologically effective and cost-effective school-based SARS-CoV-2 antigen-detection rapid diagnostic test (Ag-RDT) self-testing strategies among teachers and students.

DESIGN

Mathematical modelling and economic evaluation.

SETTING AND PARTICIPANTS

Simulated school and community populations were parameterised to Brazil, Georgia and Zambia, with SARS-CoV-2 self-testing strategies targeted to teachers and students in primary and secondary schools under varying epidemic conditions.

INTERVENTIONS

SARS-CoV-2 Ag-RDT self-testing strategies for only teachers or teachers and students-only symptomatically or symptomatically and asymptomatically at 5%, 10%, 40% or 100% of schools at varying frequencies.

OUTCOME MEASURES

Outcomes were assessed in terms of total infections and symptomatic days among teachers and students, as well as total infections and deaths within the community under the intervention compared with baseline. The incremental cost-effectiveness ratios (ICERs) were calculated for infections prevented among teachers and students.

RESULTS

With respect to both the reduction in infections and total cost, symptomatic testing of all teachers and students appears to be the most cost-effective strategy. Symptomatic testing can prevent up to 69·3%, 64·5% and 75·5% of school infections in Brazil, Georgia and Zambia, respectively, depending on the epidemic conditions, with additional reductions in community infections. ICERs for symptomatic testing range from US$2 to US$19 per additional school infection averted as compared with symptomatic testing of teachers alone.

CONCLUSIONS

Symptomatic testing of teachers and students has the potential to cost-effectively reduce a substantial number of school and community infections.

Approaches and challenges to inferring the geographical source of infectious disease outbreaks using genomic data

Genomic data hold increasing potential in the elucidation of transmission dynamics and geographical sources of infectious disease outbreaks. Phylogeographic methods that use epidemiological and genomic data obtained from surveillance enable us to infer the history of spatial transmission that is naturally embedded in the topology of phylogenetic trees as a record of the dispersal of infectious agents between geographical locations. In this Review, we provide an overview of phylogeographic approaches widely used for reconstructing the geographical sources of outbreaks of interest. These approaches can be classified into ancestral trait or state reconstruction and structured population models, with structured population models including popular structured coalescent and birth-death models. We also describe the major challenges associated with sequencing technologies, surveillance strategies, data sharing, and analysis frameworks that became apparent during the generation of large-scale genomic data in recent years, extending beyond inference approaches. Finally, we highlight the role of genomic data in geographical source inference and clarify how this enhances understanding and molecular investigations of outbreak sources.

Direct immunoassay on a polyester microwell plate for colorimetric detection of the spike protein in swab and saliva samples

This study presents the development of a polyester microplate for detecting the S-protein of the SARS-CoV-2 virus in saliva and nasopharyngeal swab samples using direct enzyme-linked immunosorbent assay (ELISA) technology. The polyester microplate was designed to contain 96 zones with a 3 mm diameter each, and a volume of 2-3 μL. The experimental conditions including reagent concentration and reaction time were optimized. The microplate image was digitized and analyzed using graphical software. The linear range obtained between protein S concentrations and pixel intensity was 0-10 μg mL-1, with a correlation coefficient of 0.99 and a limit of detection of 0.44 μg mL-1. The developed methodology showed satisfactory intraplate and interplate repeatability with RSD values lower than 7.8%. The results achieved through immunoassay performed on polyester microplates were consistent with those of the RT-PCR method and showed a sensitivity of 100% and 90% and specificity of 85.71% and 100% for saliva and nasopharyngeal samples, respectively. The proposed direct immunoassay on polyester microplates emerges as an alternative to conventional immunoassays performed on commercial polystyrene plates, given the low cost of the device, low consumption of samples and reagents, lower waste generation, and shorter analysis time. Moreover, the immunoassay has shown great potential for diagnosing COVID-19 with precision and accuracy.

Estimating the potential impact and diagnostic requirements for SARS-CoV-2 test-and-treat programs

Oral antivirals have the potential to reduce the public health burden of COVID-19. However, now that we have exited the emergency-phase of the COVID-19 pandemic, declining SARS-CoV-2 clinical testing rates (average testing rates = [Formula: see text]10 tests/100,000 people/day in low-and-middle income countries; <100 tests/100,000 people/day in high-income countries; September 2023) make the development of effective test-and-treat programs challenging. We used an agent-based model to investigate how testing rates and strategies affect the use and effectiveness of oral antiviral test-to-treat programs in four country archetypes of different income levels and demographies. We find that in the post-emergency-phase of the pandemic, in countries where low testing rates are driven by limited testing capacity, significant population-level impact of test-and-treat programs can only be achieved by both increasing testing rates and prioritizing individuals with greater risk of severe disease. However, for all countries, significant reductions in severe cases with antivirals are only possible if testing rates were substantially increased with high willingness of people to seek testing. Comparing the potential population-level reductions in severe disease outcomes of test-to-treat programs and vaccination shows that test-and-treat strategies are likely substantially more resource intensive requiring very high levels of testing (≫100 tests/100,000 people/day) and antiviral use suggesting that vaccination should be a higher priority.

Surveillance for variants of SARS-CoV-2 to inform risk assessments

Since the beginning of the coronavirus disease 2019 (COVID-19) pandemic, numerous severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants have emerged, some leading to large increases in infections, hospitalizations and deaths globally. The virus's impact on public health depends on many factors, including the emergence of new viral variants and their global spread. Consequently, the early detection and surveillance of variants and characterization of their clinical effects are vital for assessing their health risk. The unprecedented capacity for viral genomic sequencing and data sharing built globally during the pandemic has enabled new variants to be rapidly detected and assessed. This article describes the main variants circulating globally between January 2020 and June 2023, the genetic features driving variant evolution, and the epidemiological impact of these variants across countries and regions. Second, we report how integrating genetic variant surveillance with epidemiological data and event-based surveillance, through a network of World Health Organization partners, supported risk assessment and helped provide guidance on pandemic responses. In addition, given the evolutionary characteristics of circulating variants and the immune status of populations, we propose future directions for the sustainable genomic surveillance of SARS-CoV-2 variants, both nationally and internationally: (i) optimizing variant surveillance by including environmental monitoring; (ii) coordinating laboratory assessment of variant evolution and phenotype; (iii) linking data on circulating variants with clinical data; and (iv) expanding genomic surveillance to additional pathogens. Experience during the COVID-19 pandemic has shown that genomic surveillance of pathogens can provide essential, timely and evidence-based information for public health decision-making.

Development of practical techniques for simultaneous detection and distinction of current and emerging SARS-CoV-2 variants

Countless individuals have fallen victim to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and have generated antibodies, reducing the risk of secondary infection in the short term. However, with the emergence of mutated strains, the probability of subsequent infections remains high. Consequently, the demand for simple and accessible methods for distinguishing between different variants is soaring. Although monitoring viral gene sequencing is an effective approach for differentiating between various types of SARS-CoV-2 variants, it may not be easily accessible to the general public. In this article, we provide an overview of the reported techniques that use combined approaches and adaptable testing methods that use editable recognition receptors for simultaneous detection and distinction of current and emerging SARS-CoV-2 variants. These techniques employ straightforward detection strategies, including tests capable of simultaneously identifying and differentiating between different variants. Furthermore, we recommend advancing the development of uncomplicated protocols for distinguishing between current and emerging variants. Additionally, we propose further development of facile protocols for the differentiation of existing and emerging variants.

Genomic and Temporal Analysis of Deletions Correlated to qRT-PCR Dropout in N Gene in Alpha, Delta and Omicron Variants

Since the first SARS-CoV-2 outbreak, mutations such as single nucleotide polymorphisms (SNPs) and insertion/deletions (INDELs) have changed and characterized the viral genome sequence, structure and protein folding leading to the onset of new variants. The presence of those alterations challenges not only the clinical field but also the diagnostic demand due to failures in gene detection or incompleteness of polymerase chain reaction (PCR) results. In particular, the analysis of understudied genes such as N and the investigation through whole-genome next generation sequencing (WG-NGS) of regions more prone to mutate can help in the identification of new or reacquired mutations, with the aim of designing robust and long-lasting primers. In 48 samples of SARS-CoV-2 (including Alpha, Delta and Omicron variants), a lack of N gene amplification was observed in the genomes analyzed through WG-NGS. Three gene regions were detected hosting the highest number of SNPs and INDELs. In several cases, the latter can interfere deeply with both the sensitivity of diagnostic methodologies and the final protein folding. The monitoring over time of the viral evolution and the reacquisition among different variants of the same mutations or different alterations within the same genomic positions can be relevant to avoid unnecessary consumption of resources.