Dismantling myths on the airborne transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)

The coronavirus disease 2019 (COVID-19) pandemic has caused untold disruption throughout the world. Understanding the mechanisms for transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is key to preventing further spread, but there is confusion over the meaning of ‘airborne’ whenever transmission is discussed. Scientific ambivalence originates from evidence published many years ago which has generated mythological beliefs that obscure current thinking. This article collates and explores some of the most commonly held dogmas on airborne transmission in order to stimulate revision of the science in the light of current evidence. Six ‘myths’ are presented, explained and ultimately refuted on the basis of recently published papers and expert opinion from previous work related to similar viruses. There is little doubt that SARS-CoV-2 is transmitted via a range of airborne particle sizes subject to all the usual ventilation parameters and human behaviour. Experts from specialties encompassing aerosol studies, ventilation, engineering, physics, virology and clinical medicine have joined together to produce this review to consolidate the evidence for airborne transmission mechanisms, and offer justification for modern strategies for prevention and control of COVID-19 in health care and the community.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Indoor Environmen

Size-Dependent Effects of Coded Wire Tags on Mortality and Tag Retention in Redtail Culter Culter mongolicus

Redtail culter Culter mongolicus, a threatened piscivorous fish species in China's inland waters, has exhibited serious population decline. As part of a stock enhancement research project in shallow lakes of the Yangtze River basin, China, we evaluated the performance of coded wire tags (CWTs) for marking juvenile redtail culter. Through a short-term indoor experiment, we marked hatchery-reared juveniles from three size groups (mean +/- SE, small: 46.85 +/- 0.67 mm, intermediate: 53.76 +/- 0.62 mm, large: 63.42 +/- 1.05 mm) in the dorsal muscle with CWTs and tested whether marking effects on tag retention and mortality were size-specific. Tag retention was more than 98% in all the three size groups and appeared to be unaffected by fish size. Tag losses were found only within 3 d of marking. Tagging-induced mortality of small marked juveniles (58%) was significantly higher than those of intermediate (5%) and large (1%) marked juveniles and was also significantly higher than small unmarked ones (17%). The relationship of marked mortality and total length was quantitatively described by an exponential decay model. Mortality in small marked juveniles occurred mainly within 24 h after marking, which accounted for 71% of the mortality in this marked size. In order to avoid high posttagging mortality and biases in stocking assessment programs, we suggest it is worth the extra fish-culture costs to use juveniles of at least 57 mm (which displayed 90% survival in our experiment) for stocking assessment programs that utilize CWTs for a handling-sensitive species like redtail culter.Redtail culter Culter mongolicus, a threatened piscivorous fish species in China's inland waters, has exhibited serious population decline. As part of a stock enhancement research project in shallow lakes of the Yangtze River basin, China, we evaluated the performance of coded wire tags (CWTs) for marking juvenile redtail culter. Through a short-term indoor experiment, we marked hatchery-reared juveniles from three size groups (mean +/- SE, small: 46.85 +/- 0.67 mm, intermediate: 53.76 +/- 0.62 mm, large: 63.42 +/- 1.05 mm) in the dorsal muscle with CWTs and tested whether marking effects on tag retention and mortality were size-specific. Tag retention was more than 98% in all the three size groups and appeared to be unaffected by fish size. Tag losses were found only within 3 d of marking. Tagging-induced mortality of small marked juveniles (58%) was significantly higher than those of intermediate (5%) and large (1%) marked juveniles and was also significantly higher than small unmarked ones (17%). The relationship of marked mortality and total length was quantitatively described by an exponential decay model. Mortality in small marked juveniles occurred mainly within 24 h after marking, which accounted for 71% of the mortality in this marked size. In order to avoid high posttagging mortality and biases in stocking assessment programs, we suggest it is worth the extra fish-culture costs to use juveniles of at least 57 mm (which displayed 90% survival in our experiment) for stocking assessment programs that utilize CWTs for a handling-sensitive species like redtail culter

Effects of Two Anesthetics on Survival of Juvenile Culter mongolicus during a Simulated Transport Experiment

Cultivation of the redtail culter Culter mongolicus has been increasing substantially over the last decade along the Yangtze River basin; such increases in production lead to increased juvenile transportation. However, redtail culter juveniles have high transport mortality rates due to a strong stress response that is exacerbated by the accumulation of toxic metabolic waste. Through a 24-h simulated transport experiment (sampling every 6 h), we assessed effects of tricaine methanesulfonate (MS-222) at 10 mg/L of water, 20 mg/L, and 40 mg/L on redtail culter survival and water quality parameters, and similarly we assessed clove oil at 2 mg/L of water, 5 mg/L, and 10 mg/L. None of the anesthetics significantly improved water quality during the initial 6-12 h of the experiment. However, MS-222 treatments at the first 12-24 h of the experiment had significantly higher dissolved oxygen (DO), ammonia, and pH than the control but failed to decrease un-ionized ammonia content. In contrast, the clove oil treatment significantly reduced the un-ionized ammonia but failed to improve DO and pH at 12-24 h. The improvements in water quality were reflected in cumulative mortality, MS-222 and clove oil anesthetic treatments having significantly lower cumulative mortality than the control at 12-24 h. The MS-222 and clove oil slowed water quality deterioration, ensured a better transport environment, and improved juvenile survival during transportation. We recommend 5 mg/L clove oil be used when transporting juvenile redtail culters because that concentration improves fish survival while keeping cost low.Cultivation of the redtail culter Culter mongolicus has been increasing substantially over the last decade along the Yangtze River basin; such increases in production lead to increased juvenile transportation. However, redtail culter juveniles have high transport mortality rates due to a strong stress response that is exacerbated by the accumulation of toxic metabolic waste. Through a 24-h simulated transport experiment (sampling every 6 h), we assessed effects of tricaine methanesulfonate (MS-222) at 10 mg/L of water, 20 mg/L, and 40 mg/L on redtail culter survival and water quality parameters, and similarly we assessed clove oil at 2 mg/L of water, 5 mg/L, and 10 mg/L. None of the anesthetics significantly improved water quality during the initial 6-12 h of the experiment. However, MS-222 treatments at the first 12-24 h of the experiment had significantly higher dissolved oxygen (DO), ammonia, and pH than the control but failed to decrease un-ionized ammonia content. In contrast, the clove oil treatment significantly reduced the un-ionized ammonia but failed to improve DO and pH at 12-24 h. The improvements in water quality were reflected in cumulative mortality, MS-222 and clove oil anesthetic treatments having significantly lower cumulative mortality than the control at 12-24 h. The MS-222 and clove oil slowed water quality deterioration, ensured a better transport environment, and improved juvenile survival during transportation. We recommend 5 mg/L clove oil be used when transporting juvenile redtail culters because that concentration improves fish survival while keeping cost low