Minimal in-school SARS-CoV-2 transmission with strict mitigation protocols at two independent schools in Nashville, TN

BACKGROUND: The COVID-19 pandemic has greatly impacted school operations. To better understand the role of schools in COVID-19 transmission, we evaluated infections at two independent schools in Nashville, TN during the 2020-2021 school year. METHODS: The cumulative incidence of COVID-19 within each school, age group, and exposure setting were estimated and compared to local incidence. Primary attack rates were estimated among students quarantined for in-school close contact. RESULTS: Among 1401 students who attended school during the study period, 98 cases of COVID-19 were reported, corresponding to cumulative incidence of 7.0% (95% confidence interval (CI): 5.7-8.5). Most cases were linked to household (58%) or community (31%) transmission, with few linked to in-school transmission (11%). Overall, 619 students were quarantined, corresponding to >5000 person-days of missed school, among whom only 5 tested positive for SARS-CoV-2 during quarantine (primary attack rate: 0.8%, 95% CI: 0.3, 1.9). Weekly case rates at school were not correlated with community transmission. CONCLUSION: These results suggest that transmission of COVID-19 in schools is minimal when strict mitigation measures are used, even during periods of extensive community transmission. Strict quarantine of contacts may lead to unnecessary missed school days with minimal benefit to in-school transmission.

Analysis of SARS-CoV-2 transmission in different settings, among cases and close contacts from the Tablighi cluster in Brunei Darussalam

We report the transmission dynamics of SARS-CoV-2 across different settings from the initial COVID-19 cluster in Brunei, arisen from 19 attendees at the Malaysian Tablighi Jama’at gathering and resulted in 52 locally transmitted cases. Highest non-primary attack rates(ARs) were observed at a subsequent local religious gathering (14.8% [95%CI: 7.1,27.7]) and in the household (10.6% [95%CI: 7.3,15.1]. Household ARs of symptomatic cases were higher (14.4% [95%CI: 8.8,19.9]) than asymptomatic (4.4% [95%CI: 0.0,10.5]) or presymptomatic cases (6.1% [95%CI: 0.3,11.8]). Low ARs (<1%) were observed for workplace and social settings. Our analysis highlights that SARS-CoV-2 transmission varies depending on environmental, behavioural and host factors. We identify ‘red flags’ of potential super-spreading events, namely densely populated gatherings for prolonged periods in enclosed settings, presence of individuals with recent travel history, and group behaviours such as communal eating, sleeping and sharing of personal hygiene facilities. We propose differentiated testing strategies that account for transmission risk.Article summary lineWe highlight the variability of SARS-CoV-2 transmission across different settings, identify settings at highest risk, and characterize the role of environmental, behavioural, and host factors in driving SARS-CoV-2 transmission.

The β-carotene dilemma: ESR study with coordinated peroxyl radicals

The apparently unpredictable behaviour of β-carotene in the supplementation of the diet of smokers is discussed in the light of the reactions of peroxyl radicals with β-carotene in the absence of oxygen. The decay of tert-butylperoxyl radicals in the presence of β-carotene was studied at ambient temperature in non-polar solvents by ESR spectroscopy. The primary reaction in the absence of oxygen is interpreted as a spin-trapping effect of a peroxyl radical by β-carotene producing an intermediate labile free radical, which disappears after recombination with a second tert-butylperoxyl radical. The result is the transformation of β-carotene to a diamagnetic compound with two peroxy bonds. In the presence of chelating transition metals with unpaired d-electrons as electron donors the peroxy group of the oxidized β-carotene can be split to alkoxyl free radicals. The primary attack of tert-butylperoxyl radicals is completely inhibited in the presence of vitamin E followed by production of free aryloxy radicals and the presence of oxygen has no significant effect on this reaction. Spin-trapping of peroxyl radicals by the double bond of vitamin A leads to its oxidation in the absence of vitamin E.Transition metal ions such as Co, Cr, Fe, and Mn, known to be present in the aerosol of cigarette smoke, homolyse the peroxyl bonds of peroxidised β-carotene, which results in cell damage.

Waterborne epidemic outbreak of Shigella sonnei gastroenteritis in Santa Maria de Palautordera, Catalonia, Spain

In August 2002 an outbreak of Shigella sonnei infection occurred in a Spanish town of 6343 inhabitants. In total, 756 people developed acute gastroenteritis and 181 cases were shigella-confirmed. The peak incidence was during 5–6 August 2002. The estimated primary attack rate was 9·97%; the attack rate for secondary cases was 38%. The <15 years ago group was most affected (16·49%). The town and its surroundings were served by two water systems, A and B. The cases had consumed water provided by system A (attack rate 164 cases/1000 population). Microbiological analysis of water from system A did not show the presence of coliform bacteria or shigella. This shigellosis outbreak was the largest reported in Spain. The impact of the epidemic was probably greater than the incidence detected.

Responses of the Lichen Cladonia convoluta to High CO2 Level and Heavy Metal Treatment

Despite of the downward acclimation of photosynthesis in C. convoluta, increased net photosynthesis and carbon balance can be anticipated in response to elevated atmospheric CO2 level. CO2 exchange measurement seems to be more indicative when detecting heavy metal stress than fluorescence parameters. Among these, the relative fluorescence decrease ratio (RFd690) shows damage first, suggesting that the primary attack site for heavy metal ions is CO2 fixation and reaction centres are harmed last. Long-term elevated CO2 ameliorates partly this damage by improving C-balance to a greater extent in the heavy-metal stressed lichens

Mechanismus der Cyclotrimerisierung von Phenylvinylketonen und die Kristallstrukturen von 1-((1R*,2S*,3R*,5S*)-und 1-((1R*,2S*,3R*,5R*)- 3.5-Dibenzoyl-2-hydroxy-2-phenylcyclohexylmethyl)-pyrrolidin-2-on/The Mechanism of Cyclotrimerisation of Phenylvinylketones and theCrystal Structures of 1-((1R*,2S*,3R*,5S*)-and1-((1R*,2S*,3R*,5R*)-3.5-Dibenzoyl-2-hydroxy-2-phenylcyclohexylmethyl)-pyrrolidin-2-on

The cyclotrimerisation of 1-phenyl-2-propyn-1-ol (1) with pyrrolidin-2-one (2) to the tribenzoylcyclohexanes 4 and 5 produced -with modifications of the reaction conditions -the phenylvinylketone adducts 17 and 18 as intermediates and additionally the cyclohexylmethyl-pyrrolidin-2-ones 8 and 9. Obviously the mechanism consists of a primary attack of pyrrolidin-2-onat (2a) to a phenylketone (7) followed by a series of consecutive Michael reactions, which give rise to 4 and 5 as well as to 8 and 9. The latter two have been identified by X-ray crystal structure analyses. They crystallize in the monoclinic space group P21/c, Z=4, with 8: a = 1786,8(6), b = 636.7(2), c = 2280.9(8) pm, β = 102.33(3)°; 9: a = 1119.9(7), b = 1165.1(3), c = 2198.6(5) pm, β = 118.24(4)°.

Investigation of the Hardening Reaction of Gelatin with 13C Labeled Formaldehyde by Solution and Solid State 13C NMR Spectroscopy

Model reactions of the hardening of gelatin with 13C labeled formaldehyde were monitored by 13C NMR spectroscopy in solution and in the solid state. In solution primary attack of formaldehyde first forms methylols of lysine residues and later of arginine residues, which react to a lysine-arginine crosslink. During the drying process of hardened gelatin, in addition to the lysine-arginine crosslink an arginine-arginine crosslink is formed. The rate of crosslink formation is strongly influenced by humidity.