The impact of invisible-spreaders on COVID-19 transmission and work resumption

The global impact of coronavirus disease 2019 (COVID-19) is unprecedented, and many control and prevention measures have been implemented to test for and trace COVID-19. However, invisible-spreaders, who are associated with nucleic acid detection and asymptomatic infections, have received insufficient attention in the current COVID-19 control efforts. In this paper, we analyze the time series infection data for Italy, Germany, Brazil, India and Sweden since the first wave outbreak to address the following issues through a series of experiments. We conclude that: 1) As of June 1, 2020, the proportion of invisible-spreaders is close to 0.4% in Sweden, 0.8% in early Italy and Germany, and 0.4% in the middle and late stages. However, in Brazil and India, the proportion still shows a gradual upward trend; 2) During the spread of this pandemic, even a slight increase in the proportion of invisible-spreaders could have large implications for the health of the community; and 3) On resuming work, the pandemic intervention measures will be relaxed, and invisible-spreaders will cause a new round of outbreaks.

Rapid Antigen Test Combine with Nucleic Acid Detection: A Better Strategy for COVID-19 Screening at Points of Entry

The coronavirus disease 2019 (COVID-19) pandemic has imposed an enormous disease burden worldwide, and the Delta variant now has become dominant in 53 countries. Recently published studies have shown that during periods of high viral load, rapid antigen tests (RAT) yield similar results to reverse transcriptase-polymerase chain reaction (RT-PCR) tests, and when used in serial screening (e.g., every three days), it has a high sensitivity. In this perspective, we recommend RT-PCR combined with RAT at points of entry: (i) RAT can be added to the detection phase at ports of entry to detect asymptomatic infections as early as possible; (ii) RAT can be added to post-entry quarantine every three days or less to reduce the rate of missed detection in later quarantine; (iii) Adding regular RAT to regular PCR testing for key airport personnel to prevent cross-infection and conduct closed-off management. In the face of sporadic Delta variant outbreaks, the combination of the two could help rapid triage and management of suspected populations at an early stage and thus contain the outbreak more quickly and effectively. We also discuss the issue whether the current antigen detection reagents can cope with various SARS-CoV-2 variants.

Exploring the dynamic nature of divalent metal ions involved in DNA cleavage by CRISPR-Cas12a

CRISPR-Cas12a has been widely used in genome editing and nucleic acid detection. In both of these applications, Cas12a cleaves target DNA in a divalent metal ion-dependent manner. However, when and...

Diagnostic Performance of a Rapid Antigen Test Compared with the Reverse Transcription Polymerase Chain Reaction for SARS-CoV-2 Detection in Asymptomatic Individuals Referring to a Drive-in Testing Facility

Quick and reliable identification of severe acute respiratory syndrome coronavirus SARS-CoV-2 in the population is required to manage the COVID-19 pandemic. This is a prospective observational study of diagnostic accuracy. Paired swab samples from 317 asymptomatic individuals referring to a drive-in testing facility were tested in parallel by means of the rapid antigen test developed by Jiangsu Bioperfectus Technologies and routine nucleic acid detection. Overall specificity was 100% and sensitivity was 49% but reached 87% at higher viral loads (Ct < 25). In this study, the antigen detection test showed high specificity and good sensitivity in asymptomatic individuals carrying higher viral loads. The assay performance worsened with lower viral loads, making it useful when a rapidly deployable test is essential and to assess a potential risk of immediate transmission in the community, but not recommended for testing asymptomatic individuals.

Advanced CRISPR-Cas Effector Enzyme-Based Diagnostics for Infectious Diseases, Including COVID-19

Rapid and precise diagnostic tests can prevent the spread of diseases, including worldwide pandemics. Current commonly used diagnostic methods include nucleic-acid-amplification-based detection methods and immunoassays. These techniques, however, have several drawbacks in diagnosis time, accuracy, and cost. Nucleic acid amplification methods are sensitive but time-consuming, whereas immunoassays are more rapid but relatively insensitive. Recently developed CRISPR-based nucleic acid detection methods have been found to compensate for these limitations. In particular, the unique collateral enzymatic activities of Cas12 and Cas13 have dramatically reduced the diagnosis times and costs, while improving diagnostic accuracy and sensitivity. This review provides a comprehensive description of the distinct enzymatic features of Cas12 and Cas13 and their applications in the development of molecular diagnostic platforms for pathogen detection. Moreover, it describes the current utilization of CRISPR-Cas-based diagnostic techniques to identify SARS-CoV-2 infection, as well as recent progress in the development of CRISPR-Cas-based detection strategies for various infectious diseases. These findings provide insights into designing effective molecular diagnostic platforms for potential pandemics.