Symptoms associated with a positive result for a swab for SARS-CoV-2 infection among children in Alberta

BACKGROUND:Research involving children with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has primarily focused on those presenting to emergency departments. We aimed to determine the symptoms most commonly associated with a positive result for a SARS-CoV-2 swab among community-based children.METHODS:We conducted an observational study among children tested and followed for SARS-CoV-2 infection using nasal, nasopharyngeal, throat or other (e.g., nasopharyngeal aspirate or tracheal secretions, or unknown) swabs between Apr. 13 and Sept. 30, 2020, in Alberta. We calculated positive likelihood ratios (LRs) for self-reported symptoms and a positive SARS-CoV-2 swab result in the entire cohort and in 3 sensitivity analyses: all children with at least 1 symptom, all children tested because of contact tracing whether they were symptomatic or not and all children 5 years of age or older.RESULTS:We analyzed results for 2463 children who underwent testing for SARS-CoV-2 infection; 1987 children had a positive result and 476 had a negative result. Of children with a positive test result for SARS-CoV-2, 714 (35.9%) reported being asymptomatic. Although cough (24.5%) and rhinorrhea (19.3%) were 2 of the most common symptoms among children with SARS-CoV-2 infection, they were also common among those with negative test results and were not predictive of a positive test (positive LR 0.96, 95% confidence interval [CI] 0.81–1.14, and 0.87, 95% CI 0.72–1.06, respectively). Anosmia/ageusia (positive LR 7.33, 95% CI 3.03–17.76), nausea/vomiting (positive LR 5.51, 95% CI 1.74–17.43), headache (positive LR 2.49, 95% CI 1.74– 3.57) and fever (positive LR 1.68, 95% CI 1.34–2.11) were the symptoms most predictive of a positive result for a SARS-CoV-2 swab. The positive LR for the combination of anosmia/ageusia, nausea/vomiting and headache was 65.92 (95% CI 49.48–91.92).INTERPRETATION:About two-thirds of the children who tested positive for SARS-CoV-2 infection reported symptoms. The symptoms most strongly associated with a positive SARS-CoV-2 swab result were anosmia/ageusia, nausea/vomiting, headache and fever.

The refrain that “children are not small adults” certainly seems to apply in the context of coronavirus disease 2019 (COVID-19). Children are less likely to become infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) than adults and seem to experience less severe symptoms and have better prognoses.^1–4 However, some studies have suggested that reduced disease severity in children leads to them being less likely to undergo testing.⁵ Three 2020 studies highlighted that COVID-19 symptoms in children are similar to those of other acute respiratory illnesses, with fever, cough, nasal congestion, fatigue and runny nose predominating. ^6–8 On Sept. 15, 2020, the Centers for Disease Control and Prevention reported death to be an uncommon outcome in people younger than 21 years of age (0.08% of all deaths).⁹Beyond an understanding of what symptoms most commonly present in children, health care professionals and public health policy-makers could benefit from knowing which presenting symptoms are most likely to be associated with SARS-CoV-2 infection. Many jurisdictions have implemented screening questionnaires for pediatric-dominated settings such as schools. We hypothesized that some symptoms in children are more likely than others to be associated with a positive result for a test for SARS-CoV-2. We therefore assessed symptom patterns among children in Alberta who were followed by Alberta Public Health and who had swabs taken for possible SARS-CoV-2 infection, comparing those with positive results and those with negative results to estimate symptom frequencies and prognostic import of symptoms in a large cohort and in 3 subgroups.     

Holographic microscopy provides new insights into the settlement of zoospores of the green alga Ulva linza on cationic oligopeptide surfaces

Interaction of zoospores of Ulva linza with cationic, arginine-rich oligopeptide self-assembled monolayers (SAMs) is characterized by rapid settlement. Some spores settle (ie permanently attach) in a ‘normal’ manner involving the secretion of a permanent adhesive, retraction of the flagella and cell wall formation, whilst others undergo ‘pseudosettlement’ whereby motile spores are trapped (attached) on the SAM surface without undergoing the normal metamorphosis into a settled spore. Holographic microscopy was used to record videos of swimming zoospores in the vicinity of surfaces with different cationic oligopeptide concentrations to provide time-resolved insights into processes associated with attachment of spores. The data reveal that spore attachment rate increases with increasing cationic peptide content. Accordingly, the decrease in swimming activity in the volume of seawater above the surface accelerated with increasing surface charge. Three-dimensional trajectories of individual swimming spores showed a ‘hit and stick’ motion pattern, exclusively observed for the arginine-rich peptide SAMs, whereby spores were immediately trapped upon contact with the surface.     

Respiration rates in heterotrophic,free-living protozoa

Published estimates of protozoan respiratory rates are reviewed with the object of clarifying their value in ecological studies. The data show a surprisingly large variance when similarly sized cells or individual species are compared. This is attributed to the range of physiological states in the cells concerned. The concept of basal metabolism has little meaning in protozoa. During balanced growth, energy metabolism is nearly linearly proportional to the growth rate constant; at the initiation of starvation, metabolic rate rapidly declines. Motility requires an insignificant fraction of the energy budget of protozoans. For growing cells, metabolic rate is approximately proportional to weight^0.75 and the data fall nearly exactly on a curve extrapolated from that describing the respiration rates of poikilotherm metazoans as a function of body weight. It is conceivable that protozoan species exist with lower maximum potential growth and metabolic rates than those predicted from cell volume and the equations derived from the available data. However, the lack of information concerning the state of the cells studied prevents verification of this idea. Laboratory measurements of protozoan respiratory rates have no predictive value for protozoa in nature other than delimiting a potential range. For small protozoans, this range may, on an individual basis, represent a factor of 50.