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Tag: transmission
January 19, 2021
Household Transmission of SARS-CoV-2 and Risk Factors for Susceptibility and Infectivity in Wuhan: A Retrospective Observational Study
A retrospective cohort study using contact tracing records from more than 27,000 households in Wuhan, China through April 18 estimated an overall SARS-CoV-2 attack rate among people living in the same household of 16%, assuming a mean incubation period of 5 days and a maximum infectious period of 22 days. Individuals ≥60 years old were…
January 15, 2021
Emergence of SARS-CoV-2 B.1.1.7 Lineage — United States, December 29, 2020–January 12, 2021. MMWR
A more highly transmissible variant of SARS-CoV-2, lineage B.1.1.7, has been confirmed to have caused 76 cases in at least 10 states in the US as of January 13, 2021. Models suggest that this variant has potential to drive a new phase of exponential growth in cases in the US, and that even if vaccination…
January 14, 2021
Estimating Internationally Imported Cases during the Early COVID-19 Pandemic
Combined daily COVID-19 prevalence and flight passenger volume were used to estimate importations of SARS-CoV-2 from China. Researchers estimated that Wuhan was the primary source of global case importation from China in early January, but shifted to 18 other Chinese cities as the source in mid-February, particularly for importations to African destinations. The authors estimate…
Emergence and Evolution of a Prevalent New SARS-CoV-2 Variant in the United States
[pre-print, not peer reviewed] Genomic virus surveillance has identified one of the most prevalent SARS-CoV-2 variants in the US, referred to as 20C-US. Earliest 20C-US genomes have been traced in the southern US as early as late May. 20C-US has acquired up to 7 non-synonymous mutations with implications for efficient and accurate virus production, including…
January 13, 2021
Serologic Surveillance and Phylogenetic Analysis of SARS-CoV-2 Infection in Hospital Health Care Workers
[Pre-print, not peer-reviewed] A prospective study of 801 healthcare workers (HCW) conducted from May-June 2020 found that SARS-CoV-2 incidence was highest in HCW working in COVID-19 patient care (13%), as compared with non-COVID-19 patient care (7%, HR=2.2) and not working in patient care (4%, HR=3.9). Within the group caring for COVID-19 patients, SARS-CoV-2 cumulative incidence…
Duration and Key Determinants of Infectious Virus Shedding in Hospitalized Patients with Coronavirus Disease-2019 (COVID-19)
A study of 129 hospitalized individuals who had been diagnosed with COVID-19 by RT-PCR detected infectious virus shedding by viral culture in 23 patients (18%), with infectious virus shedding for a median of 8 days after onset of symptoms. Multivariate analyses identified viral loads above 7 log10 RNA copies/mL as independently associated with isolation of infectious…
January 11, 2021
Team-to-Team Transmission of COVID-19 in Ice Hockey Games – a Case Series of Players in Finnish Ice Hockey Leagues
An outbreak of SARS-CoV-2 among U-20 ice hockey teams in Finland was reported based on public statements by the local health authorities and the teams involved. One player who had asymptomatic COVID-19 infected 22 of 28 teammates. The team had returned from an away trip the day before the first players had symptoms. COVID-19 was…
Incidence and Secondary Transmission of SARS-CoV-2 Infections in Schools
Very limited within-school transmission of SARS-CoV-2 was found in the first 9 weeks of in-person instruction in North Carolina secondary schools between August and October 2020. There were 773 community-acquired infections documented by molecular testing in the 11 school districts with over 90,000 students and staff. Through contact tracing, health department staff identified an additional…
January 8, 2021
Early Transmissibility Assessment of the N501Y Mutant Strains of SARS-CoV-2 in the United Kingdom, October to November 2020
A model incorporating information from genome sequencing and other epidemiological data suggests that the SARS-CoV-2 mutant strain 501Y Variant 2, which became the dominant strain in England in November and December 2020, has an R0 1.75-times that of the 501N variant, meaning that it is 75% more transmissible. Because of limited genetic sequence data, the…
SARS-CoV-2 Transmission From People Without COVID-19 Symptoms
A mathematical model estimates that 59% of all transmission of SARS-CoV-2 comes from asymptomatic cases, suggesting that strategies based on identifying and isolating symptomatic people will not control the pandemic. The model estimates that 35% of SARS-CoV-2 transmission comes from presymptomatic individuals and 24% from individuals who never become symptomatic. Johansson et al. (Jan 7,…
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