Study of the fate of viruses on the filters of the air hundling unit : influence of the process parameters and impact on health

La pollution de l'air est l'un des principaux problèmes de santé publique de notre siècle et surtout de l'air intérieur alors que nous passons environ 90% de notre temps dans des environnements fermés. Parmi les polluants les bioaérosols ont été peu étudiés. Cependant des études épidémiologiques ont déjà montré une relation entre les bioaérosols et la santé. Le but de cette thèse est d’étudier les virus respiratoires dans les milieux clos via les systèmes de ventilation. A l’issue d’un état de l’art des polluants de l’air, il est important de définir ceux nécessitant d’être traités, les systèmes de ventilation, les procédés de filtration par médias fibreux et les procédés de traitement pouvant être mis en oeuvre. Les effets des bioaérosols viraux dans les environnements intérieurs sur la santé publique ont été discutés dans une revue bibliographique. Une méthodologie a été mise en oeuvre pour étudier le comportement des virus dans une centrale de traitement de l’air (CTA). Les virus respiratoires, mengovirus (virus nu à ARN de la même famille que les rhinovirus responsables du rhume) et adénovirus (virus respiratoire nu à ADN), ont été choisis et étudiés dans un système expérimental miniature représentatif des systèmes de traitement d’air. La performance de filtration d’un filtre de CTA vis-à-vis des aérosols viraux a été évaluée avec une validation du système expérimental utilisé. Cette étude a montré la capacité des virus de passer à travers le filtre tout en restant infectieux. Peu de littérature existant sur le sujet, ce projet a permis d’ajouter de nouvelles données pertinentes quant à la persistance des virus respiratoires dans l’air intérieur et plus précisément au niveau des filtres dans les centrales de traitement d’air.Air pollution is one of the major public health problems of our century and especially of indoor air as we spend about 90% of our time in closed environments. Among pollutants bioaerosols have been poorly studied. However, epidemiological studies have already shown a relationship between bioaerosols and human health. The aim of this PhD work is to learn about respiratory viruses in closed environments via ventilation systems in order to study indoor air quality. At the end of state of the art of air pollutants, it is important to define those present in the air that need to be treated, ventilation systems, filtration processes by fibrous media and the processing methods being able to be implemented. The effects of viral bioaerosols on public health in indoor environments were discussed and drafted in a bibliographic review. The methodology of the study was to assess the fate of respiratory viruses, mengoviruses and adenoviruses, in a miniature experimental system similar to air treatment systems used in closed environments. The experimental system used was validated and the filter performance against viral aerosols was investigated. This study presented originality for the characterization and the fate of two non-enveloped respiratory viruses, mengovirus (RNA) and adenovirus (DNA), in indoor environments and their fate on fiber glass filter. This study showed the ability of viruses to pass through the filter and to remain infectious upstream and downstream the filter. There is scarce literature on this subject, and this project allowed us to add new relevant data on the persistence of respiratory viruses in indoor air and more precisely at the level of filters in air handling units

Respiratory viruses' fate on filters of air handling units

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The persistence of respiratory viruses on filters of air handling units

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Adenovirus behavior in air handling unit fiberglass filters

International audienceViral aerosols can lead to respiratory viral infections with high infectivity. About 90% of people’s time is spent in closed environments. A few studies have pointed out that the ventilation systems in air handling units (AHUs) that treat and transmit a new synthetic clean and conditioned environment can also spread and transport viral particles in buildings. The aim of this work is to study the characterization of adenovirus, a DNA non-enveloped respiratory virus, on the F7 fiberglass filter used in AHUs. In this study, an experimental setup simulating an AHU was used. The SYBR® QPCR, Electrical Low-Pressure Impactor (ELPI™) and Scanning Mobility Particle Sizer (SMPS™) were used to detect, measure and characterize the aerosolized adenovirus solution. The characterization results showed that the nebulized adenovirus could be aerosolized in different forms associated or not with cell debris and proteins. The quantification and level of infectivity of adenovirus demonstrated that viruses passed through filters and remained infectious up- and downstream of the system during the 25 min of aerosolization. This study showed that AHUs should be considered an indoor source of viral contamination. © 2019, Springer Nature B.V

The fate of mengovirus on fiberglass filter of air handling units

International audienceOne of the most important topics that occupy public health problems is the air quality. That is the reason why mechanical ventilation and air handling units (AHU) were imposed by the different governments in the collective or individual buildings. Many buildings create an artificial climate using heating, ventilation and airconditioning (HVAC) systems. Among the existing aerosols in the indoor air, we can distinguish the bioaerosol with biological nature such as bacteria, viruses, fungi. Respiratory viral infections are a major public health issue because they are usually highly infective. We spend about 90% of our time in closed environments such as homes, workplaces or transport. Some studies have shown that AHU contribute to the spread and transport of viral particles within buildings. The aim of this work is to study the characterization of viral bioaerosols in indoor environments and to understand the fate of mengovirus eukaryote RNA virus on glass fiber filter F7 used in AHU. In this study, a setup close to reality of AHU system was used. The mengovirus aerosolized was characterized and measured with the Electrical Low Pressure Impact (ELPI) and the Scanner Mobility Particle Size (SMPS) and detected with RT-qPCR. The results about quantification and the level of infectivity of mengovirus on the filter and in the biosampler showed that mengovirus can pass through the filter and remain infectious upstream and downstream the system. Regarding the virus effectiveness on the filter under a constant air flow, and mengovirus was remained infectious during 10 hours after aerosolization

Comparaison du comportement et caractérisation de deux bioaerosols viraux sur les filtres d'une centrale de traitement de l'air (CTA)

International audienceIndoor air pollution is one of the main public health problems of our century. Air is a vector transporting microorganisms like viruses from outdoors to indoors. The aim of this work is to understand the fate and the persistence of respiratory viruses on filters used in air handling units (AHU). As a model respiratory virus, Mengovirus and Adenovirus were aerosolized in a vertical column with outputs equipped with a fiberglass filter F7. Viral particles passing through the filter are collected by a BioSampler. The detection of virus particles and the study of viability on the filters were made by qPCR and TCID50 respectively.La pollution de l'air intérieur est l'un des principaux problèmes de santé publique de notre siècle. L'air est un vecteur transportant des microorganismes comme les virus de l'extérieur à l'intérieur. Le but de ce travail est de comprendre le devenir et la persistance des virus respiratoires sur les filtres utilisés dans les centrales de traitement de l'air (CTA). En tant que modèle de virus respiratoire, Mengovirus et Adenovirus ont été aérosolisés dans une colonne verticale avec des sorties équipées d'un filtre à fibre de verre F7. Les particules virales qui traversent le filtre sont collectées par BioSampler. La détection des particules virales et l'étude de la viabilité sur les filtres ont été effectuées respectivement par qPCR et TCID50

Faustoviruses: Comparative Genomics of New Megavirales Family Members

International audienceAn emerging interest for the giant virus discovery process, genome sequencing and analysis has allowed an expansion of the number of known Megavirales members. Using the protist Vermarnoeba sp. as cell support, a new giant virus named Faustovirus has been isolated. In this study, we describe the genome sequences of nine Faustoviruses and build a genomic comparison in order to have a comprehensive overview of genomic composition and diversity among this new virus family. The average sequence length of these viruses is 467,592.44 bp (ranging from 455,803 to 491,024 bp), making them the fourth largest Megavirales genome after Mimiviruses. Pandoraviruses, and Pithovirus sibericum. Faustovirus genomes displayed an average G+C content of 37.14 % (ranging from 36.22 to 39.59%) which is close to the G+C content range of the Asfarvindae genomes (38%). The proportion of best matches and the phylogenetic analysis suggest a shared origin with Asfarviridae without belonging to the same family. The core-gene-based phylogeny of Faustoviruses study has identified four lineages. These results were confirmed by the analysis of amino acids and COGs category distribution. The diversity of the gene composition of these lineages is mainly explained by gene deletion or acquisition and some exceptions for gene duplications. The high proportion of best matches from Bacteria and Phycodnaviridae on the pan-genome and unique genes may be explained by an interaction occurring after the separation of the lineages. The Faustovirus core-genome appears to consolidate the surrounding of 207 genes whereas the pan-genome is described as an open pan-genome, its enrichment via the discovery of new Faustoviruses is required to better seize all the genomic diversity of this family