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ImportanceUnderstanding feasibility of rapid testing in congregate living setting provides critical data to reduce the risk of outbreaks in these settings. ObjectiveUse rapid antigen screening to detect SARS-CoV-2 in an asymptomatic group of university students and staff. DesignCross-sectional SettingUniversity of British Columbia, Vancouver, Canada. ParticipantsStudents and staff living or working in congregate housing. InterventionHealth care professional administered rapid antigen test Main Outcomes and measuresUse of BD Veritor rapid antigen testing and asymptomatic participants experiences with rapid testing ResultsA total of 3536 BD Veritor tests were completed in 1141 unique individuals. One third of participants completed between two to four tests and 21% were screened five or more times. The mean number of tests completed per person was three. The mean length of time between those who had more than one test was seven days. There were eight false positives and 25 PCR confirmed COVID-19 positive individuals identified through this work. All individuals reported having no symptoms that they attributed to COVID-19. Almost all (n=22, 88%) COVID-19 positive cases were found in male participants. A total of 86 additional students from multiple different student residences (n=9) were asked to self-isolate while they waited for their COVID-19 diagnostic test results. An average of seven additional students positive for COVID-19 living in congregate housing were identified through contact tracing by finding one positive case. Conclusions and relevanceRapid testing is a relatively inexpensive and operationally easy method of identifying asymptomatic individuals with COVID-19.

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BackgroundCOVID-19 is a highly transmissible infectious disease that has infected over 122 million individuals worldwide. To combat this pandemic, governments around the world have imposed lockdowns. However, the impact of these lockdowns on the rates of COVID-19 transmission in communities is not well known. Here, we used COVID-19 case counts from 3,000+ counties in the United States (US) to determine the relationship between lockdown as well as other county factors and the rate of COVID-19 spread in these communities. MethodsWe merged county-specific COVID-19 case counts with US census data and the date of lockdown for each of the counties. We then applied a Functional Principal Component (FPC) analysis on this dataset to generate scores that described the trajectory of COVID-19 spread across the counties. We used machine learning methods to identify important factors in the county including the date of lockdown that significantly influenced the FPC scores. FindingsWe found that the first FPC score accounted for up to 92.81% of the variations in the absolute rates of COVID-19 as well as the topology of COVID-19 spread over time at a county level. The relation between incidence of COVID-19 and time at a county level demonstrated a hockey-stick appearance with an inflection point approximately 7 days prior to the county reporting at least 5 new cases of COVID-19; beyond this inflection point, there was an exponential increase in incidence. Among the risk factors, lockdown and total population were the two most significant features of the county that influenced the rate of COVID-19 infection, while the median family income, median age and within-county move also substantially affect COVID spread. InterpretationLockdowns are an effective way of controlling the COVID-19 spread in communities. However, significant delays in lockdown cause a dramatic increase in the case counts. Thus, the timing of the lockdown relative to the case count is an important consideration in controlling the pandemic in communities. Research in contextO_ST_ABSEvidence before this studyC_ST_ABSWe searched PubMed using the term "coronavirus", OR "COVID-19", OR "COVID-19 infection", OR "SARS-CoV-2" combined with "Lockdown" or "sociodemographic factor" or "Vulnerability" for original articles published before March 18, 2021. Similar searches were done in medRxiv, Google Scholar, and Web of Science. Only papers published in English were reviewed. The most similar relevant works to our study were Acharya et al.1 and Karmakar et al.2, which investigated the associations between population-level social factors and COVID-19 incidence and mortality. Unlike our current study, which employed a longitudinal design, both of studies were cross-sectional in nature and thus fixed on a single time point. In addition, neither of these studies investigated the impact of lockdown measures on COVID-19 infection patterns. Another relevant study is Alfano et al.s work3, which focused on the efficacy of lockdown on COVID-19 case rates. However, this study did not evaluate the timing of lockdown on this endpoint. Added value of this studyTo our knowledge, this is the first study to use functional principal component analysis (FPCA) to investigate COVID-19 infection trajectories (in a longitudinal manner) and their relationships with different sociodemographic factors and lockdown policy at a county level. The FPCA transformed a longitudinal vector with high-dimensions into a "single" surrogate variable, which retained 93% of the information. We used an advanced statistical model (segmented regression) to investigate the effects of lockdown on incidence of COVID-19 across the US. We found that the relationship had a "hockey stick" appearance with an inflection point at [~]7 days prior to a county reporting at least 5 cases of COVID-19. We also applied a machine learning model (i.e., elastic net) to explore joint effects of lockdown and other sociodemographic factors on COVID-19 infection patterns, which estimated the impact of each of factors, adjusted for each other. Implications of all the available evidenceOur study suggests that lockdown is an effective policy to reduce case counts of COVID-19 in communities; however, significant delays in its implementation result in exponential growth of COVID-19. The inflection point is approximately 7 days prior to a county reporting at least 5 cases of COVID-19. These data will help policy-makers to determine the optimal timing of lockdowns for their communities.

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ObjectivesTo use human genetic variants that proxy angiotensin-converting enzyme (ACE) inhibitor drug effects and cardiovascular risk factors to provide insight into how these exposures affect lung ACE2 and TMPRSS2 gene expression and circulating ACE2 levels. DesignTwo-sample Mendelian randomization (MR) analysis. SettingSummary-level genetic association data. ParticipantsParticipants were predominantly of European ancestry. Variants that proxy ACE inhibitor drug effects and cardiometabolic risk factors (body mass index, chronic obstructive pulmonary disease, lifetime smoking index, low-density lipoprotein cholesterol, systolic blood pressure and type 2 diabetes mellitus) were selected from publicly available genome-wide association study data (sample sizes ranging from 188,577 to 898,130 participants). Genetic association estimates for lung expression of ACE2 and TMPRSS2 were obtained from the Gene-Tissue Expression (GTEx) project (515 participants) and the Lung eQTL Consortium (1,038 participants). Genetic association estimates for circulating plasma ACE2 levels were obtained from the INTERVAL study (4,947 participants). Main outcomes and measuresLung ACE2 and TMPRSS2 expression and plasma ACE2 levels. ResultsThere were no association of genetically proxied ACE inhibition with any of the outcomes considered here. There was evidence of a positive association of genetic liability to type 2 diabetes mellitus with lung ACE2 gene expression in GTEx (p = 4x10-4) and with circulating plasma ACE2 levels in INTERVAL (p = 0.03), but not with lung ACE2 expression in the Lung eQTL Consortium study (p = 0.68). There were no associations between genetically predicted levels of the other cardiometabolic traits with the outcomes. ConclusionsThis study does not provide evidence to support that ACE inhibitor antihypertensive drugs affect lung ACE2 and TMPRSS2 expression or plasma ACE2 levels. In the current COVID-19 pandemic, our findings do not support a change in ACE inhibitor medication use without clinical justification. Summary boxesO_ST_ABSWhat is already known on this topicC_ST_ABSO_LISevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the current coronavirus disease 2019 (COVID-19) pandemic. C_LIO_LISerine protease TMPRSS2 is involved in priming the SARS-CoV-2 spike protein for cellular entry through the angiotensin-converting enzyme 2 (ACE2) receptor. C_LIO_LIExpression of ACE2 and TMPRSS2 in the lung epithelium might have implications for risk of SARS-CoV-2 infection and severity of COVID-19. C_LI What this study addsO_LIWe used human genetic variants that proxy ACE inhibitor drug effects and cardiometabolic risk factors to provide insight into how these exposures affect lung ACE2 and TMPRSS2 expression and circulating ACE2 levels. C_LIO_LIOur findings do not support the hypothesis that ACE inhibitors have effects on ACE2 expression. C_LIO_LIWe found some support for an association of genetic liability to type 2 diabetes mellitus with higher lung ACE2 expression and plasma ACE2 levels, but evidence was inconsistent across studies. C_LI

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OBJECTIVE: To investigate the effect of simulated stiff knee on the gait parameters. METHOD: Twenty healthy male adults were recruited. The temporospatial, kinematic & kinetic parameters and energy consumption were analyzed under three different conditions which were free gait, fixed knee flexion in neutral position and limited knee flexion to 30 degrees using knee orthosis. RESULTS: When knee flexion was fixed in neutral position, the cadence and walking speed significantly decreased, and the step time, step width, O2 cost significantly increased compared to free gait. When knee flexion was limited or fixed in neutral position, the kinematic and kinetic parameters in pelvis, hip, knee and ankle joints significantly changed compared with free gait. CONCLUSION: Simulated stiff-knee may affect not only knee joint but also pelvis, hip and ankle joints with increased energy consumption. These findings help us to understand the compensatory mechanism and energy conservation of stiff-knee gait.

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OBJECTIVE: The aim of this study was to investigate the characteristics of prosthetic gait of unilateral transfemoral amputees on an inclined surface compared with those of normal persons. METHOD: Five male unilateral transfemoral amputees and ten normal persons were recruited. Uphill and downhill walking of inclined surface on slopes of 10 and 20 degrees and level walking were investigated. Kinematic data were obtained with VICON 370 system (Oxford Metrics Ltd., UK). RESULTS: The kinematic data of the transfemoral amputees showed significantly decreased peak hip extension at all situation and peak hip flexion at 20 degrees uphill walking, significant increased knee extension at 20 degrees downhill and all uphill walking, and significant decreased knee flexion at all situation, and significant decreased ankle dorsiflexion at all situation and plantarflexion at all situation except 20 degrees downhill walking compared with those of normal persons. Also they showed significant decreased cadence, speed and increased step time, double support at all situation compared with normal persons. CONCLUSION: Analysis of prosthetic gait of unilateral transfemoral amputees on an inclined surface support the basic data for induction of normal gait pattern.

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OBJECTIVE: To investigate the kinematic and kinetic characteristics of stair ascent in patients with knee osteoarthritis. METHOD: Twenty patients with knee osteoarthritis and twenty healthy controls were recruited. The kinematic and kinetic data were obtained through a three dimensional motion analyzer. The kinematic and kinetic data during stair ascent were compared between two groups. RESULTS: The total required time of stair ascent was significantly longer in the osteoarthritis group than that of the control group (p<0.05). In comparison with the control group, the angle of maximal pelvis anterior tilting, minimal and maximal hip flexion and minimal knee flexion were significantly increased (p<0.05). However, the angle of knee flexion and ankle dorsiflexion at initial contact were significantly decreased in the osteoarthritis group (p<0.05). The maximal moment and power of knee extension and ankle plantarflexion were significantly decreased in the osteoarthritis group (p<0.05). Sixteen patients (80.0%) in the osteoarthritis group showed flexion arc after initial contact. "W" sign was shown in 16 patients (80.0%). CONCLUSION: We found the unique kinematic and kinetic patterns during stair ascent in patients with knee osteoarthritis, and that knee osteoarthritis influence not only kinematic and kinetic patterns of knee but also those of hip and ankle.

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OBJECTIVE: To evaluate the changes of kinematic gait patterns at long-term follow up study after selective posterior rhizotomy (SPR) in children with spastic diplegic cerebral palsy. METHOD: Eighteen children with spastic diplegic cerebral palsy participated in this study. Gait patterns on sagittal plane were studied before and at average 3.5 years after SPR. Kinematic and temporospatial data were obtained by the VICON 370 system. RESULTS: The spasticity of hip adductor and ankle plantar flexor were improved significantly after SPR. The maximal angle of pelvic tilt, ankle dorsiflexion angle at initial contact, peak ankle dorsiflexion angle during stance phase, at toe-off and during swing phase, mid-range point of flexion-extension motion on ankle were significantly improved after SPR. The temporospatial data tended to improve after SPR at long-term follow up. CONCLUSION: The SPR reduced spasticity and the gait pat terns were improved in children with spastic diplegic cere bral palsy at long-term follow up.

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