It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow,measured in air change per hour(ACH).However,increasing ACH d...It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow,measured in air change per hour(ACH).However,increasing ACH did not effectively prevent the spread of COVID-19.To better understand the role of ACH and airflow large-scale patterns,a comprehensive fully transient computational fluid dynamics(CFD)simulation of two-phase flows based on a discrete phase model(DPM)was performed in a university classroom setting with people present.The investigations encompass various particle sizes,ventilation layouts,and flow rates.The findings demonstrated that the particle size threshold at which particles are deemed airborne is highly influenced by the background flow strength and large-scale flow pattern,ranging from 5µm to 10µm in the cases investigated.The effects of occupants are significant and must be precisely accounted for in respiratory particle transport studies.An enhanced ventilation design(UFAD-CDR)for university classrooms is introduced that places a premium on mitigating airborne disease spread.Compared to the baseline design at the same ACH,this design successfully reduced the maximum number density of respiratory particles by up to 85%.A novel airflow-related parameter,Horizontality,is introduced to quantify and connect the large-scale airflow pattern with indoor aerosol transport.This underscores that ACH alone cannot ensure or regulate air quality.In addition to the necessary ACH for air exchange,minimizing horizontal bulk motion is essential for reducing aerosol transmissibility within the room.展开更多
Influenza A virus(IAV)shows an extensive host range and rapid genomic variations,leading to continuous emergence of novel viruses with significant antigenic variations and the potential for cross-species transmission....Influenza A virus(IAV)shows an extensive host range and rapid genomic variations,leading to continuous emergence of novel viruses with significant antigenic variations and the potential for cross-species transmission.This causes global pandemics and seasonal flu outbreaks,posing sustained threats worldwide.Thus,studying all IAVs'evolutionary patterns and underlying mechanisms is crucial for effective prevention and control.We developed FluTyping to identify IAV genotypes,to explore overall genetic diversity patterns and their restriction factors.FluTyping groups isolates based on genetic distance and phylogenetic relationships using whole genomes,enabling identification of each isolate's genotype.Three distinct genetic diversity patterns were observed:one genotype domination pattern comprising only H1N1 and H3N2 seasonal influenza subtypes,multi-genotypes cocirculation pattern including majority avian influenza subtypes and swine influenza H1N2,and hybrid-circulation pattern involving H7N9 and three H5 subtypes of influenza viruses.Furthermore,the IAVs in multi-genotypes cocirculation pattern showed region-specific dominant genotypes,implying the restriction of virus transmission is a key factor contributing to distinct genetic diversity patterns,and the genomic evolution underlying different patterns was more influenced by host-specific factors.In summary,a comprehensive picture of the evolutionary patterns of overall IAVs is provided by the FluTyping's identified genotypes,offering important theoretical foundations for future prevention and control of these viruses.展开更多
基金This research was supported by the Airborne Disease Transmission Research Cluster(ADTRC),which is funded by the UBC Eminence program.The authors gratefully acknowledge the use of Digital Research Alliance of Canada resources for CFD simulations.
文摘It has been widely accepted that the most effective way to mitigate airborne disease transmission in an indoor space is to increase the ventilation airflow,measured in air change per hour(ACH).However,increasing ACH did not effectively prevent the spread of COVID-19.To better understand the role of ACH and airflow large-scale patterns,a comprehensive fully transient computational fluid dynamics(CFD)simulation of two-phase flows based on a discrete phase model(DPM)was performed in a university classroom setting with people present.The investigations encompass various particle sizes,ventilation layouts,and flow rates.The findings demonstrated that the particle size threshold at which particles are deemed airborne is highly influenced by the background flow strength and large-scale flow pattern,ranging from 5µm to 10µm in the cases investigated.The effects of occupants are significant and must be precisely accounted for in respiratory particle transport studies.An enhanced ventilation design(UFAD-CDR)for university classrooms is introduced that places a premium on mitigating airborne disease spread.Compared to the baseline design at the same ACH,this design successfully reduced the maximum number density of respiratory particles by up to 85%.A novel airflow-related parameter,Horizontality,is introduced to quantify and connect the large-scale airflow pattern with indoor aerosol transport.This underscores that ACH alone cannot ensure or regulate air quality.In addition to the necessary ACH for air exchange,minimizing horizontal bulk motion is essential for reducing aerosol transmissibility within the room.
基金supported by the National Key Plan for Scientific Research and Development of China(2021YFC2301305 and 2021YFC2302001)the National Natural Science Foundation of China(32370703,92169106,9216910042 and 32070678)+2 种基金the CAMS Innovation Fund for Medical Science(2022-I2M-1-021,2021-I2M-1-051)the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences(2021-PT180-001)the Emergency Key Program of Guangzhou Laboratory(grant EKPG21-12).
文摘Influenza A virus(IAV)shows an extensive host range and rapid genomic variations,leading to continuous emergence of novel viruses with significant antigenic variations and the potential for cross-species transmission.This causes global pandemics and seasonal flu outbreaks,posing sustained threats worldwide.Thus,studying all IAVs'evolutionary patterns and underlying mechanisms is crucial for effective prevention and control.We developed FluTyping to identify IAV genotypes,to explore overall genetic diversity patterns and their restriction factors.FluTyping groups isolates based on genetic distance and phylogenetic relationships using whole genomes,enabling identification of each isolate's genotype.Three distinct genetic diversity patterns were observed:one genotype domination pattern comprising only H1N1 and H3N2 seasonal influenza subtypes,multi-genotypes cocirculation pattern including majority avian influenza subtypes and swine influenza H1N2,and hybrid-circulation pattern involving H7N9 and three H5 subtypes of influenza viruses.Furthermore,the IAVs in multi-genotypes cocirculation pattern showed region-specific dominant genotypes,implying the restriction of virus transmission is a key factor contributing to distinct genetic diversity patterns,and the genomic evolution underlying different patterns was more influenced by host-specific factors.In summary,a comprehensive picture of the evolutionary patterns of overall IAVs is provided by the FluTyping's identified genotypes,offering important theoretical foundations for future prevention and control of these viruses.
