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Topic: Transmission
August 5, 2020
Evidence-Based Considerations Exploring Relations between SARS-CoV-2 Pandemic and Air Pollution: Involvement of PM2.5-Mediated Up-Regulation of the Viral Receptor ACE-2
A correlation analysis of air quality and COVID-19 incidence and mortality in Italy suggested that higher concentrations of fine particulate matter (PM2.5) corresponded temporally with higher COVID-19 incidence, mortality, and case fatality ratios across 110 geographic areas in Northern Italy. The infection rate tripled for PM2.5 levels increasing from 10 to 25 µg/m3 and the case fatality doubled for PM2.5 levels increasing from 10 to 22 µg/m3. The authors propose a potential mechanism for this observation due to…
August 4, 2020
Transmission of SARS-CoV-2 in Australian Educational Settings: A Prospective Cohort Study
Transmission between laboratory-confirmed pediatric (≤18) and adult COVID-19 cases from schools and early childhood education care (ECEC) setting and close contacts was examined in South Wales, Australia. Close contacts (n=1448) of infectious cases (n=27; n=12 children, n=15 adults) were followed to measure transmission. Close contacts were quarantined at home for 14 days, monitored, and offered testing if…
August 3, 2020
In-Flight Transmission Cluster of COVID-19: A Retrospective Case Series
Yang et al. described a case series of 12 people who likely acquired SARS-CoV-2 on a 5-hour flight carrying 325 passengers and crew members. All passengers and crew were asymptomatic and without fever at the time of boarding. A single passenger was found to be febrile on arrival in China and tested positive for SARS-CoV-2. Consequently, all passengers and crew were quarantined and monitored for 14 days. Eleven additional passengers subsequently tested positive for SARS-CoV-2; no…
Household Transmission of SARS-CoV-2 a Systematic Review and Meta-Analysis of Secondary Attack Rate
[Preprint, not peer-reviewed] Madewell et al. performed a meta-analysis of 40 studies of SARS-CoV-2 household secondary attack rate (SAR). Overall, the estimated mean SAR for household contacts was 19% (95%CI 15%–23%) and family contacts was 18% (13%–35%), both with significant heterogeneity. SARs were significantly higher from symptomatic index cases than asymptomatic index cases (20% vs. 1%), to adult contacts than to child contacts…
July 31, 2020
Observations of the Global Epidemiology of COVID-19 from the Prepandemic Period Using Web-Based Surveillance: A Cross-Sectional Analysis
Identifying cases of COVID-19 using official websites, press releases, press conference transcripts, and social media feeds of national ministries of health, Dawood et al. conclude that travelers to China, Italy, or Iran accounted for almost two-thirds of the first reported cases in 99 other countries. Although clusters of household transmission associated with these index cases were common,…
SARS-CoV-2 Transmission and Infection Among Attendees of an Overnight Camp — Georgia, June 2020
An outbreak investigation in an overnight camp in Georgia found evidence of widespread transmission of SARS-CoV-2 among children of all ages. SARS-CoV-2 tests were available for 344 of 597 camp attendees, of whom 260 (76%) were positive. The overall attack rate was 44% (260 of 597). The attack rate was 51% among those aged 6–10 years, 44% among those aged 11–17 years, and 33%…
July 30, 2020
Secondary Attack Rate of COVID-19 in Household Contacts: Systematic Review
A systematic review (13 articles) showed that the household secondary attack rate of COVID-19 varies widely across countries with a range of 5%–50%, unaffected by confounders such as population of the country, lockdown status and geographic location. The symptomatic status of the index case was strongly associated with the secondary attach rate, with very low transmission probability during the asymptomatic phase. The review suggested greater vulnerability of spouses and the elderly population to secondary transmission compared…
Age-Related Differences in Nasopharyngeal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Levels in Patients With Mild To Moderate Coronavirus Disease 2019 (COVID-19)
Heald-Sargent et al. followed a cohort of children and adults (n=145) with mild to moderate COVID-19 who were tested for SARS-CoV-2 within one week of symptom onset and found that the youngest children (<5 years) had high amounts of SARS-CoV-2 viral RNA in their nasopharynx (median cycle threshold 6.5 [4.8-12.0]) compared with older children (11.1 [6.3-15.7]) and adults adults (11.0 [6.9-17.5]). These differences correspond to a 10-fold to 100-fold greater amount of SARS-CoV-2 in the respiratory tract of the youngest children. Heald-Sargent et al. (July…
The Risk of COVID-19 Transmission in Train Passengers: An Epidemiological and Modelling Study
The risk of SARS-CoV-2 transmission among train passengers varied considerably depending on shared travel time and seat location, with a peak attack rate of 4% among passengers who were sitting adjacent to an index case. Transmission risk increased with longer duration of co-travel, increasing by 1.3% per hour for adjacent passengers. These findings are based on an analysis of the spatial and temporal distribution…
July 28, 2020
Estimation of Viral Aerosol Emissions From Simulated Individuals With Asymptomatic to Moderate Coronavirus Disease 2019
A modeling study indicated that an individual with COVID-19 who is coughing or breathing normally releases large numbers of viruses, but the estimated infectious risk from an individual with a typical viral load in a space the size of a medical exam room was low. Riediker and Tsai simulated the release of viruses from individuals with asymptomatic to moderate COVID-19 infection during normal breathing and while coughing. Viral loads across different droplet sizes…
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