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- Alsved, Malin, et al.
(författare)
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Aerosolization and recovery of viable murine norovirus in an experimental setup
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Noroviruses are the major cause for viral acute gastroenteritis in the world. Despite the existing infection prevention strategies in hospitals, the disease continues to spread and causes extensive and numerous outbreaks. Hence, there is a need to investigate the possibility of airborne transmission of norovirus. In this study, we developed an experimental setup for studies on the infectivity of aerosolized murine norovirus (MNV), a model for the human norovirus. Two aerosol generation principles were evaluated: bubble bursting, a common natural aerosolization mechanism, and nebulization, a common aerosolization technique in laboratory studies. The aerosolization setup was characterized by physical and viral dilution factors, generated aerosol particle size distributions, and the viral infectivity after aerosolization. We found a lower physical dilution factor when using the nebulization generator than with the bubble bursting generator. The viral dilution factor of the system was higher than the physical dilution; however, when comparing the physical and viral dilution factors, bubble bursting generation was more efficient. The infectivity per virus was similar using either generation principle, suggesting that the generation itself had a minor impact on MNV infectivity and that instead, the effect of drying in air could be a major reason for infectivity losses.
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| 3. |
- Alsved, Malin, et al.
(författare)
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Exhaled respiratory particles during singing and talking
- 2020
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 1521-7388 .- 0278-6826. ; 54:11, s. 245-1248
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Tidskriftsartikel (refereegranskat)abstract
- Choir singing has been suspended in many countriesduring the Covid-19 pandemic due to incidental reportsof disease transmission. The mode of transmission has been attributed to exhaled droplets, but with the exception of a study on tuberculosis from1968, there is presently almost no scientific evidence ofincreased particle emissions from singing. A substantial number of studies have,however, investigated aerosols emitted from breathing,talking, coughing and sneezing. It has also been shown that justnormal breathing over time can generate more viablevirus aerosol than coughing, since the latter is a less fre-quent activity.Compared to talking, singing often involves continu-ous voicing, higher sound pressure, higher frequencies,deeper breaths, higher peak airflows and more articu-lated consonants. All these factors are likely to increaseexhaled emissions.The aim of this study was to investigate aerosol anddroplet emissions during singing, as compared to talking and breathing. We also examined the presence of SARS-CoV-2 in the air from breathing, talking and singing,and the efficacy of face masks to reduce emissions. In this study we defined aerosol particles as having a drysize in the range 0.5–10mm. Although debatable from anaerosol physics point of view, a cutoff diameter between5 and 10mm is normally used in medicine for classifica-tion of aerosol versus droplet route of transmission. Droplets are here defined as exhaled particles, frommicron size with no upper size limit, and measured dir-ectly at the mouth before complete evaporation, thuspartly in liquid phase.
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| 5. |
- Alsved, Malin, et al.
(författare)
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Natural sources and experimental generation of bioaerosols : Challenges and perspectives
- 2020
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Ingår i: Aerosol Science and Technology. - : Informa UK Limited. - 0278-6826 .- 1521-7388. ; 54:5, s. 547-571
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Forskningsöversikt (refereegranskat)abstract
- Experimental aerosol generation methods aim to represent natural processes; however, the complexity is not always captured and unforeseen variability may be introduced into the data. The current practices for natural and experimental aerosol generation techniques are reviewed here. Recommendations for best practice are presented, and include characterization of starting material and spray fluid, rational selection of appropriate aerosol generators, and physical and biological characterization of the output aerosol. Reporting of bioaerosol research should capture sufficient detail to aid data interpretation, reduce variation, and facilitate comparison between research laboratories. Finally, future directions and challenges in bioaerosol generation are discussed.
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| 7. |
- Alsved, Malin, et al.
(författare)
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Sources of Airborne Norovirus in Hospital Outbreaks
- 2020
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Ingår i: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1537-6591 .- 1058-4838. ; 70:10, s. 2023-2028
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Noroviruses are the major cause of viral gastroenteritis. Disease transmission is difficult to prevent and outbreaks in healthcare facilities commonly occur. Contact with infected persons and contaminated environments are believed to be the main routes of transmission. However, noroviruses have recently been found in aerosols and airborne transmission has been suggested. The aim of our study was to investigate associations between symptoms of gastroenteritis and presence of airborne norovirus, and to investigate the size of norovirus carrying particles.METHODS: Air sampling was repeatedly performed close to 26 patients with norovirus infections. Samples were analysed for norovirus RNA by RT-qPCR. The times since the patients' last episodes of vomiting and diarrhoea were recorded. Size separating aerosol particle collection was also performed in ward corridors.RESULTS: Norovirus RNA was found in 21 (24%) of 86 air samples from 10 different patients. Only air samples during outbreaks, or before a succeeding outbreak, tested positive for norovirus RNA. Airborne norovirus RNA was also strongly associated with a shorter time period since the last vomiting episode (odds ratio 8.1, p=0.04 within 3 hours since the last vomiting episode). The concentration of airborne norovirus ranged from 5-215 copies/m3, and detectable amounts of norovirus RNA were found in particles <0.95 µm and >4.51 µm.CONCLUSIONS: The results suggest that recent vomiting is the major source of airborne norovirus and imply a connection between airborne norovirus and outbreaks. The presence of norovirus RNA in submicrometre particles indicates that airborne transmission can be an important transmission route.
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| 8. |
- Alsved, Malin
(författare)
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Transmission of Infectious Bioaerosols : Sources, transport and prevention strategies for airborne viruses and bacteria
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Infectious diseases that can be transmitted via air often spread rapidly, sometimes causing large epidemic and pandemic outbreaks. As an increasing number of people live in crowded urban environments, and with frequent and long-distance traveling across the world, infectious diseases can spread even faster. Yet, our knowledge of how much airborne transmission (here defined as aerosol particles <100 µm that contain infectious agents) contributes to the spreading of diseases is scarce and frequently debated. The aim of this thesis was to increase knowledge about the sources and airborne transport of infectious bioaerosols in order to prevent diseases from spreading via air. To identify possible sources of infectious bioaerosols, we collected air samples in hospitals for detection of bacteria (in operating rooms) and norovirus (in hospital wards) and correlated the results with possible source events. To study bacterial viability and viral infectivity after airborne transport, we developed an experimental setup in the laboratory where aerosolized model organisms were examined. The setup was also used to evaluate the particle collection efficiency of a novel bioaerosol sampler. In addition, three types of high-airflow ventilation systems for operating rooms were compared for their ability to maintain clean air during ongoing surgery.The median bacterial concentrations measured in operating rooms ranged from 0 to 22 CFU m-3 (colony forming units) depending on the sampling point and ventilation type. However, no correlations were found between bacterial concentrations and the number of door openings or the number of people present in the room. Based on the comparison of three types of ventilation, we concluded that the two ventilation techniques with the incoming airflow above the operating table, directed downwards, resulted in lower bacterial concentrations close to the wound than the ventilation based on turbulent mixing.We detected norovirus RNA in air samples collected in hospitals during outbreaks of the winter vomiting disease. Our results showed a significantly higher risk of finding norovirus RNA in the air within a short time (3 h) after a patient vomited. From size-separated sampling, norovirus was detected in aerosol particles >4.5 µm and <0.94 µm, indicating that norovirus has the potential to remain airborne for hours and spread in indoor environments. To evaluate the infectivity of airborne norovirus, murine norovirus was used as a model organism in a laboratory study. The infectivity of murine norovirus relative to the virus genome copy number was reduced by two orders of magnitude when aerosolized by either twin-fluid nebulization or bubble bursting. We proposed that aerosol droplet drying from a low-solute solution caused the loss of viral infectivity. A similar experimental setup, was used to study the viability of Pseudomonas syringae in air with varying levels of relative humidity. The bacterial survival was higher when aerosolized into air with low relative humidity, corresponding to rapid drying. For detection of bioaerosol sources in the field, we evaluated the particle collection efficiency of a novel electrostatic bioaerosol sampler. Owing to the small liquid collection volume of ~0.3 mL, the new bioaerosol sampler had higher sample concentrations than a commonly used impinger when collecting microspheres of sizes >1 µm.Airborne transmission of infectious diseases has long been neglected; however, as new infectious diseases emerge, knowledge that can be generalized across organism types is highly valuable. With this research, I highlight its importance, in particular for nosocomial infections, by showing that sufficient concentrations of bacteria and viruses are present in hospital air that can trigger new infections, and that bacteria and viruses aerosolized under controlled laboratory conditions remain viable and infectious. Finally, I also show that by choosing appropriate preventive measures, such as room ventilation, airborne microbial concentrations can be significantly reduced, limiting transmission of airborne disease.
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