Alliance for Pandemic Preparedness

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Topic: Transmission

June 9, 2021

Ct Values Do Not Predict SARS-CoV-2 Transmissibility in College Students

PCR cycle threshold (Ct) values, a proxy measurement for viral load, were not significantly different between SARS-CoV-2-infected individuals with at least one confirmed infected contact (i.e., spreaders) (n=94) and infected individuals with no infected contacts (i.e., non-spreaders) (n=101) in a retrospective study of routine screening data from Tulane University obtained between September and October 2020…

Exposures Associated with SARS-CoV-2 Infection in France: A Nationwide Online Case-Control Study

SARS-CoV-2 infection risk was associated with having frequented bars and restaurants (OR=1.95) or attending private gatherings (aOR=1.57), according to a multivariate analysis of an online survey administered in France to SARS-CoV-2-infected adults (n=3,426). Survey participants were matched to non-infected controls (n=1713) from October to November by age, sex, population density, and time period. Having one…

June 7, 2021

Early Epidemiological Signatures of Novel SARS-CoV-2 Variants Establishment of B.1.617.2 in England

[Pre-print, not peer-reviewed] A study in the UK suggested that many SARS-CoV-2 cases were S-gene positive, a pattern associated with the B.1.617.2 variant, which the authors suggest may become dominant over B.1.1.7. In early 2021, the majority of positive SARS-CoV-2 tests in England were genomically sequenced (74% in April 2021), with the sequencing subject to…

Comparative Household Secondary Attack Rates Associated with B.1.1.7 B.1.351 and P.1 SARS-CoV-2 Variants

[Pre-print, not peer-reviewed] A study conducted in Ontario, Canada found that household secondary attack rates were 20.2% for wild-type, 25.1% for B.1.1.7, 27.2% for B.1.351 or P.1, and 23.3% for non-variants of concern (VOC) mutations in SARS-CoV-2. Cases were grouped into households based on reported residential address: 7,555 (28%) were wild-type, 17,058 (63%) were B.1.1.7,…

June 4, 2021

Interim Estimates of Increased Transmissibility Growth Rate and Reproduction Number of the Covid-19 B.1.617.2 Variant of Concern in the United Kingdom

[Pre-print, not peer-reviewed] A modeling study found that the effective reproduction number of B.1.617.2 (WHO label Delta, first described in India) is almost certainly higher than that of B.1.1.7 (WHO label Alpha). The study used genomically sequenced cases from the UK diagnosed between March and May 2021 and excluded recent travelers in order to reflect…

COVID-19 Transmission in Group Living Environments and Households

A study of persons with recent contact with patients with SARS-CoV-2 (N=4,550) found that risk of transmission was highest among persons living in dormitories (28%) and was similar for persons with household contact (13%) and those with close contact outside of their residence (11%). The transmission rate in these three groups were significantly higher than…

June 3, 2021

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

In a longitudinal study of 76 dogs and cats living with at least one SARS-CoV-2 infected human in Texas, 4 pets were PCR-positive for SARS-CoV-2, while 14 pets had detectable anti-SARS-CoV-2 neutralizing antibodies (including 2 of the 4 PCR-positive pets). Re-sampling showed persistent PCR positivity up to 25 days and sequencing of PCR samples showed…

May 26, 2021

Estimating Infectiousness throughout SARS-CoV-2 Infection Course

An analysis of 936,423 SARS-CoV-2 RT-PCR-positive samples from hospitalized and non-hospitalized persons in Germany found that high viral loads (> 109 copies per swab) were found in 8% of subjects, 1/3 of whom were pre-symptomatic, asymptomatic, or mildly symptomatic. The mean number of days from onset of viral shedding to peak viral load was 4.3….

May 24, 2021

SARS-CoV-2 B.1.1.7 and B.1.351 Spike Variants Bind Human ACE2 with Increased Affinity

SARS-CoV-2 B.1.1.7 and B.1.351 variants were found to have 2- and 4.6-times higher binding affinity, respectively, for the human ACE2 receptor than the wildtype virus. The authors suggest that this may explain some of the observed increased transmissibility of these variants.   Ramanathan et al. (May 2021). SARS-CoV-2 B.1.1.7 and B.1.351 Spike Variants Bind Human ACE2 with…

COVID-19 Mitigation Practices and COVID-19 Rates in Schools Report on Data from Florida New York and Massachusetts

[Pre-print, not peer-reviewed] A report of SARS-CoV-2 mitigation practices and infection rates in schools in Florida, New York, and Massachusetts during the 2020-2021 school year found higher infection rates among students attending schools with lower in-person density, but no association with rates among staff. The authors suggest these results could be attributed to a protective…

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