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Background Understanding the drivers of SARS-CoV-2 transmission is crucial for control policies but evidence of transmission rates in different settings remains limited. Methods We conducted a systematic review to estimate secondary attack rates (SAR) and observed reproduction numbers (Robs) in different settings exploring differences by age, symptom status, and duration of exposure. To account for additional study heterogeneity, we employed a Beta-Binomial model to pool SARs across studies and a Negative-binomial model to estimate Robs. Results Households showed the highest transmission rates, with a pooled SAR of 21.1% (95%CI:17.4%-24.8%). SARs were significantly higher where the duration of household exposure exceeded 5 days compared with exposure of ≤5 days. SARs related to contacts at social events with family and friends were higher than those for low-risk casual contacts (5.9% vs. 1.2%). Estimates of SAR and Robs for asymptomatic index cases were approximately a seventh, and for pre-symptomatic two thirds of those for symptomatic index cases. We found some evidence for reduced transmission potential both from and to individuals under 20 years of age in the household context, which is more limited when examining all settings. Conclusions Our results suggest that exposure in settings with familiar contacts increases SARS-CoV-2 transmission potential. Additionally, the differences observed in transmissibility by index case symptom status and duration of exposure have important implications for control strategies such as contact tracing, testing and rapid isolation of cases. There was limited data to explore transmission patterns in workplaces, schools, and care-homes, highlighting the need for further research in such settings.

Background/Aims: In 2003, we reported on a small number of patients in whom acute aortic dissection appeared to be causally related to intense weight lifting. If additional cases could be identified, the phenomenon of weight lifting induced aortic dissection would be further substantiated. We now report a substantially larger number of cases in which aortic dissection is associated with intense physical exertion. Methods: Additional cases of acute aortic dissection occurring at the time of intense physical exertion were accumulated and analyzed. Cases were culled from retrospective review of a large university data base and from reports forwarded to our attention from around the country. We determined type of activity bringing on symptoms, age and sex of the patients, location of the dissection (ascending or descending aorta), aortic size, therapy, and survival. Results: We identified 31 patients in whom acute aortic dissection occurred in the context of severe physical exertion, predominantly weight lifting or similar activities. All patients except one were males. Mean age was 47.3 (range = 19–76). All except four dissections were in the ascending aorta. Only three patients (9.7%) had a family history of aortic disease. Mean aortic diameter on the initial imaging study was 4.63 cm. Twenty-six of the 31 cases were diagnosed ante-mortem and 5 post-mortem. Overall, 10 of the 31 patients (32.2%) died. Of 24 patients reaching surgical therapy, 20 (83.3%) survived. Conclusion: Weight lifting related acute aortic dissection appears to be a real phenomenon, with increasing evidence for the association of extreme exertion with this catastrophic aortic event. Moderate aortic dilatation confers vulnerability to exertion-related aortic dissection. Individuals with known aortic dilatation should be cautioned to refrain from weight lifting or strenuous exertion. Routine echocardiographic screening of individuals engaging in heavy strength training should be considered, in order to prevent this tragic loss of life.

Crystallization at production scale is typically a poorly understood unit operation, with little implementation of the first principles aspect of crystallization in its design, optimization, and control. Problems with production crystallizers include the following: (1) inconsistencies of batch-to-batch in terms of the size and number of crystals produced and (2) the purity profile (residual impurities in crystals, or wrong polymorph or chiral purity). This can have a significant impact both on product quality and downstream process unit operations including filtration, drying, milling, and product formulation. This contribution reviews typical problems encountered in production crystallization, with case studies, advice, and strategies to understand and avoid these problems through the use of in situ crystallization characterization tools.