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Topic: Transmission
March 10, 2021
Transmission Infectivity and Antibody Neutralization of an Emerging SARS-CoV-2 Variant in California Carrying a L452R Spike Protein Mutation
[Pre-print, not peer-reviewed] Whole genome sequencing of 2,172 remnant nasal/nasopharyngeal swab samples from 44 counties in California identified a novel SARS-CoV-2 variant characterized by three mutations in the spike protein named B.1.427/B.1.429 or 20C/L452R. This variant emerged around May 2020, and by January 29, 2021 represented >50% of sequenced cases, exhibiting an estimated 19-24% increase…
March 8, 2021
SARS-CoV-2 Transmission in Intercollegiate Athletics Not Fully Mitigated with Daily Antigen Testing
[Pre-print, not peer-reviewed] Two SARS-CoV-2 outbreaks occurred among US university athletic programs during the fall 2020 despite mandatory directly observed daily antigen testing, suggesting that antigen testing alone may not be sufficient to prevent outbreaks in congregate settings. In the first outbreak, 32 confirmed cases occurred within an athletics program after the index patient attended…
March 5, 2021
Just 2% of SARS-CoV-2-Positive Individuals Carry 90% of the Virus Circulating in Communities
[Pre-print, not peer-reviewed] An analysis of saliva specimens collected through a campus-wide surveillance program for SARS-CoV-2 among students at the University of Colorado, Boulder during the Fall academic semester of 2020 found that 2% (1,405 of 72,500 specimens tested) of the samples were positive for SARS-CoV-2. All of the positive students self-reported no symptoms on…
March 3, 2021
Persistent SARS-CoV-2 RNA Shedding without Evidence of Infectiousness: A Cohort Study of Individuals with COVID-19
A study of SARS-CoV-2 viral shedding showed that while most (97%) of people with mild to moderate COVID-19 continue to shed viral RNA for more than 10 days after symptom onset, virus could not be recovered by cell culture in any of the 35 individuals sampled more than 10 days after symptom onset. The authors…
Estimation of Secondary Household Attack Rates for Emergent SARS-CoV-2 Variants Detected by Genomic Surveillance at a Community-Based Testing Site in San Francisco
[Pre-print, not peer-reviewed] Some SARS-CoV-2 variants circulating in San Francisco with increasing prevalence may spread more efficiently to household contacts when compared to prior variants. Using SARS-CoV-2 genomic sequencing and epidemiological data collected from a walk-up rapid testing site in San Francisco, household contacts exposed to individuals infected with certain variants (including those with mutations…
March 2, 2021
Household COVID-19 Risk and in-Person Schooling
[Pre-print, not peer-reviewed] School-based mitigation measures reduced the odds of reporting COVID-19 like illness (CLI) and/or a positive SARS-CoV-2 PCR test result among household members living with a child attending in-person learning, according to an online survey of over 2 million US respondents conducted between November 2020 to January 2021. While the risk of reporting…
Reducing COVID-19 Airborne Transmission Risks on Public Transportation Buses An Empirical Study on Aerosol Dispersion and Control
[Pre-print, not peer-reviewed] Mask wearing in a transit or school bus setting could reduce the overall particle count released into the bus by an average of 50% or more (depending on mask quality), and could reduce the dispersion distance by several feet, according to an experimental study. The study conducted 84 test runs totaling 124…
March 1, 2021
SARS-CoV-2 Spike D614G Change Enhances Replication and Transmission
The SARS-CoV-2 S-614G variant was found to enhance binding to recombinant human ACE2 receptors, increase replication in lung and nasal cell culture systems, increase replication in a humanized ACE2 mouse model, and increased transmissibility in hamster and ferret SARS-CoV-2 models. While this mutation resulted in small increases in binding and replication in vitro, it conferred…
Household Transmission of SARS-CoV-2
A retrospective cohort study of COVID-19 risk among exposed children and adults in households where an index case was diagnosed found an overall infection risk of 10.1%, with median time to diagnosis of 3 days after positive diagnosis of the index case. The study used home addresses recorded in electronic health records to identify the…
Incubation Period for COVID-19: A Systematic Review and Meta-Analysis
A systematic review and meta-analysis (n = 15 studies, 6,300 patients) estimated that the incubation period for SARS-CoV-2 is 5.7 days (range: 5.2-6.3 days). Data were included through March 31, 2020, and most of the studies included in the meta-analysis used different parametric distributions for calculating the pooled incubation period. Rai et al. (Feb 23,…
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