| 1. |
- 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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| 2. |
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| 3. |
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| 4. |
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| 5. |
- Alsved, Malin, et al.
(författare)
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Airborne bacteria in hospital operating rooms during ongoing surgery
- 2018
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Konferensbidrag (refereegranskat)abstract
- IntroductionPost-operative infections obtained from open-wound surgeries constitute an unnecessary load on both healthcare and affected patients. It is well established that increased air cleanliness reduces the number of post-operative infections. Therefore, the ventilation system is important in order to reduce the number of infectious particles in the air during surgery. Ventilation with high airflow, as in operating rooms, consumes a high amount of energy and it is thus desirable to find energy efficient solutions. ObjectivesThe purpose of this work was to evaluate air quality, energy efficiency and working environment comfort for three different ventilation techniques in operating rooms. MethodThe newly developed ventilation system temperature controlled airflow (TcAF) was compared with the conventionally used turbulent mixed airflow (TMA) and laminar airflow (LAF). In total, 750 air sample measurements were performed during 45 orthopaedic operations: 15 for each type of ventilation system [1]. The concentration of colony forming units (CFU)/m3 was measured at three locations in the rooms: close to the wound (<0.5 m), at the instrument table and peripherally in the room. The working environment comfort was evaluated in a questionnaire.ResultsOur study shows that both LAF and TcAF maintains CFU concentrations in the air during ongoing surgery significantly below 10 CFU/m3 at the wound and at the instrument table, and for TcAF also in the periphery of the room, see Figure 1. The median CFU concentration in TMA was at or above 10 CFU/m3 at all locations. TcAF used less than half the airflow to that of LAF, resulting in a 28% reduction in energy consumption. The working environment comfort was perceived less noisy and having less draft in the TcAF than the LAF ventilation.SummaryBoth the LAF and TcAF ventilation maintain high air cleanliness with low CFU concentrations throughout the operation. TMA is less efficient in removing bacteria from the air close to the patient.
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| 9. |
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| 10. |
- Alsved, Malin, et al.
(författare)
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Droplet, aerosol and SARS-CoV-2 emissions during singing and talking
- 2021
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Konferensbidrag (refereegranskat)abstract
- IntroductionAs the pandemic continues to spread, more knowledge is needed about the viral transmission routes. Several super spreading events during the Covid-19 pandemic have been linked to singing in choirs and talking loud. However, in the beginning of the pandemic there was only one study about emitted aerosols and droplets from singing, published in 1968, and only a handful on emissions from talking. Therefore, we conducted a study to measure the aerosol and droplet emissions from talking and singing. We also evaluated the emissions from singing when wearing a face mask.We have further developed our setup so that we collect the aerosol particles from Covid-19 infected patients that are talking and singing, and analyze our samples for SARS-CoV-2, the virus causing Covid-19.MethodTwelve healthy singers (7 professionals, 5 amateurs) were included in the first study part on quantifying the amount of emitted aerosols and droplets. The singers were singing or talking a short consonant rich text repeatedly at a constant pitch with their face in the opening of a funnel. The aerosol particle size and concentration was measured from the other end of the funnel using an aerodynamic particle sizer (APS, 3321, TSI Inc). In addition, the amount of un-evaporated droplets were captured with a high-speed camera and quantified using image analysis.During February and March 2021 we will collect aerosol particles from patients with confirmed Covid-19 that are singing and talking into a funnel. We will use a growth tube condensation collector, a BioSpot (Aerosol Devices), operating at 8 L min-1, and a NIOSH BC-251 cyclone sampler operating at 3.5 L min-1 (TISCH Environmental). The BioSpot collects the whole range of exhaled aerosol particles with high (95%) efficiency into liquid, and the NIOSH cyclone sampler collects particles into three size fractions: <1 µm (filter), 1-4 µm (liquid), >4 µm (liquid). The APS is again used to measure size and concentration of the emitted aerosol particles, so that emissions from infected test subjects can be compared with those of the healthy test subjects. Air samples will be analyzed for detection of SARS-CoV-2 genes, and if possible, SARS-CoV-2 infectivity in cell cultures.ResultsAerosol particle emissions from healthy test subjects were significantly higher during normal singing (median 690, range [320–2870] particles/s) than during normal talking (270 [120–1380] particles/s) (Wilcoxon’s signed rank test, p=0.002). Loud singing produced even more aerosol particles (980 [390–2870] particles/s) than normal singing (p=0.002). The amount of non-evaporated droplets detected by the high-speed camera setup showed similar results: more droplets during loud singing or talking. For both aerosol particle concentrations and droplet numbers, the levels were reduced by on average 70-80% when wearing a surgical face mask.ConclusionsSinging and talking give rise to high aerosol and droplet emissions from the respiratory tract. This is likely an important transmission route for Covid-19. In our upcoming part of the study we hope to determine how much SARS-CoV-2 that is emitted during these social activities.
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| 11. |
- Alsved, Malin, et al.
(författare)
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Effect of Aerosolization and Drying on the Viability of Pseudomonas syringae Cells
- 2018
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Airborne dispersal of microorganisms influences their biogeography, gene flow, atmospheric processes, human health and transmission of pathogens that affect humans, plants and animals. The extent of their impact depends essentially on cell-survival rates during the process of aerosolization. A central factor for cell-survival is water availability prior to and upon aerosolization. Also, the ability of cells to successfully cope with stress induced by drying determines their chances of survival. In this study, we used the ice-nucleation active, plant pathogenic Pseudomonas syringae strain R10.79 as a model organism to investigate the effect of drying on cell survival. Two forms of drying were simulated: drying of cells in small droplets aerosolized from a wet environment by bubble bursting and drying of cells in large droplets deposited on a surface. For drying of cells both in aerosol and surface droplets, the relative humidity (RH) was varied in the range between 10 and 90%. The fraction of surviving cells was determined by live/dead staining followed by flow cytometry. We also evaluated the effect of salt concentration in the water droplets on the survival of drying cells by varying the ionic strength between 0 and 700 mM using NaCl and sea salt. For both aerosol and surface drying, cell survival increased with decreasing RH (p < 0.01), and for surface drying, survival was correlated with increasing salt concentration (p < 0.001). Imaging cells with TEM showed shrunk cytoplasm and cell wall damage for a large fraction of aerosolized cells. Ultimately, we observed a 10-fold higher fraction of surviving cells when dried as aerosol compared to when dried on a surface. We conclude that the conditions, under which cells dry, significantly affect their survival and thus their success to spread through the atmosphere and colonize new environments as well as their ability to affect atmospheric processes.
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| 12. |
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| 13. |
- 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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| 14. |
- Alsved, Malin, et al.
(författare)
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Experimental and computational evaluation of airborne bacteria in hospital operating rooms with high airflows
- 2018
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Ingår i: Proceedings of The 5<sup>th</sup> Working & Indoor Aerosols Conference 18-20 April 2018; Cassino, Italy.
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Konferensbidrag (refereegranskat)abstract
- Post-operative infections after surgery can be decreased by the use of efficient ventilation with clean air. In this study, we investigated three types of operating room ventilation: turbulent mixed airflow(TMA), laminar airflow (LAF) and a new type of ventilation named temperature controlled airflow(TcAF). Measurements of airborne bacteria were made during surgery and compared with values calculated by computational fluid dynamics (CFD). The results show that LAF and TcAF are most efficient in removing bacteria around the patient. With LAF, there are large differences in bacterial loads, depending on location in the room.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
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| 19. |
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| 20. |
- Alsved, Malin, et al.
(författare)
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Infectivity of exhaled SARS-CoV-2 aerosols is sufficient to transmit covid-19 within minutes
- 2023
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Ingår i: Scientific Reports. - 2045-2322. ; 13
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Tidskriftsartikel (refereegranskat)abstract
- Exhaled SARS-CoV-2-containing aerosols contributed significantly to the rapid and vast spread of covid-19. However, quantitative experimental data on the infectivity of such aerosols is missing. Here, we quantified emission rates of infectious viruses in exhaled aerosol from individuals within their first days after symptom onset from covid-19. Six aerosol samples from three individuals were culturable, of which five were successfully quantified using TCID50. The source strength of the three individuals was highest during singing, when they exhaled 4, 36, or 127 TCID50/s, respectively. Calculations with an indoor air transmission model showed that if an infected individual with this emission rate entered a room, a susceptible person would inhale an infectious dose within 6 to 37 min in a room with normal ventilation. Thus, our data show that exhaled aerosols from a single person can transmit covid-19 to others within minutes at normal indoor conditions.
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| 21. |
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| 22. |
- 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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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in aerosol particles exhaled from COVID-19 infected patients during breathing, talking and singing
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the beginning of the COVID-19 pandemic, several super spreader events occurred during singing in choirs, which lead to an increased attention to airborne transmission of SARS-CoV-2, the virus causing COVID-19. Since then, aerosol generation from singing has been studied in more detail, however, only from healthy subjects. In this study, we collected aerosol particles in the exhaled breath of 40 COVID-19 infected patients during breathing, talking and singing, respectively, and analysed the samples for detection of SARS-CoV-2.MethodPatients that were contacted by the COVID-19 testing service due to a positive test result were asked to volunteer for the study. A team of researchers drove a small truck hosting a mobile laboratory to the home address of the patient to perform exhaled breath aerosol collection using a condensational particle collector (BioSpot, Aerosol Devices) and a two-stage cyclone sampler (NIOSH bc-251, Tisch Environmental). Samples were collected for 10 min each when the patient was breathing, talking and singing, respectively.All samples were stored at -80°C until RNA extraction and analysis by reverse transcription quantitative polymerase chain reaction (RT-qPCR) targeting the N-gene.ResultsA first screening of air samples collected with the BioSpot showed that SARS-CoV-2 could be detected in the exhaled aerosols from three of nine patients during singing or talking. Two of these samples contained 103 and 104 viral RNA copies, corresponding to a viral emission rate of approximately 4 and 25 viruses per second, respectively. Samples from the remaining 31 patients are to be analysed during the spring. We hope to contribute to quantifying and understanding the Covid-19 transmission via the airborne route.This study was approved by the Swedish Ethics Review Authority (2020-07103). This work was supported by AFA Insurances and the Swedish Research Council FORMAS.
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| 27. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in aerosol particles exhaled from COVID-19 infected patients during breathing, talking and singing
- 2021
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Konferensbidrag (refereegranskat)abstract
- In the beginning of the COVID-19 pandemic, several super spreader events occurred during choir singing, which lead to an increased attention to airborne transmission of SARS-CoV-2. Since then, aerosol generation from singing has been studied in detail, however, mainly from healthy subjects. In this study, we collected aerosol particles in the exhaled breath of 38 COVID-19 infected patients during breathing, talking and singing, respectively, and analyzed the samples for detection of SARS-CoV-2.MethodPatients that were contacted by the COVID-19 testing service due to a positive test result early in the phase of their infection (median 2, range: 0-6 days from symptom onset) were asked to volunteer for the study. A team of researchers drove a small truck hosting a mobile laboratory to the home address of the patient to perform exhaled breath aerosol collection using a condensational particle collector (BioSpot, Aerosol Devices) and a two-stage cyclone sampler (NIOSH bc-251, Tisch Environmental). Samples were collected for 10 min each when the patients were breathing, talking and singing, respectively. In addition, patient samples from nasopharynx and saliva were collected, and patients filled out a questionnaire about symptoms. All samples were stored at -80 °C until RNA extraction and analysis by reverse transcription quantitative polymerase chain reaction (RT-qPCR) targeting the N-gene.ResultsA first preliminary screening of air samples collected with the BioSpot showed that SARS-CoV-2 could be detected in the exhaled aerosols from 14 of 38 (37%) patients during respiratory activities. 50% of patients in the early phase of the infection, day 0-1 from symptom onset, emitted detectable levels of airborne SARS-CoV-2 RNA, 35% of patients on day 2-3, and 0% of patients on day 4-6. The highest viral RNA concentrations in aerosol samples were found in those collected during singing. Further analysis is ongoing and we hope that our results will contribute to quantifying and understanding the Covid-19 transmission via the airborne route.This study was approved by the Swedish Ethics Review Authority (2020-07103). This work was supported by AFA Insurances and the Swedish Research Council FORMAS.
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| 28. |
- Alsved, Malin, et al.
(författare)
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SARS-CoV-2 in exhaled aerosol particles from covid-19 cases and its association to household transmission
- 2022
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Ingår i: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. - : Oxford University Press (OUP). - 1537-6591. ; 75:1, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Covid-19 transmission via exhaled aerosol particles has been considered an important route for the spread of infection, especially during super-spreading events involving loud talking or singing. However, no study has previously linked measurements of viral aerosol emissions to transmission rates.METHODS: During Feb-Mar 2021, covid-19 cases that were close to symptom onset were visited with a mobile laboratory for collection of exhaled aerosol particles during breathing, talking and singing, respectively, and of nasopharyngeal and saliva samples. Aerosol samples were collected using a BioSpot-VIVAS and a NIOSH bc-251 two-stage cyclone, and all samples were analyzed by RT-qPCR for SARS-CoV-2 RNA detection. We compared transmission rates between households with aerosol-positive and aerosol-negative index cases.RESULTS: SARS-CoV-2 RNA was detected in at least one aerosol sample from 19 of 38 (50%) included cases. The odds ratio of finding positive aerosol samples decreased with each day from symptom onset (OR 0.55, 95CI 0.30-1.0, p=0.049). The highest number of positive aerosol samples were from singing, 16 (42%), followed by talking, 11 (30%), and the least from breathing, 3 (8%). Index cases were identified for 13 households with 31 exposed contacts. Higher transmission rates were observed in households with aerosol-positive index cases, 10/16 infected (63%), compared to households with aerosol-negative index cases, 4/15 infected (27%) (Chi-square test, p=0.045).CONCLUSIONS: Covid-19 cases were more likely to exhale SARS-CoV-2-containing aerosol particles close to symptom onset and during singing or talking as compared to breathing. This study supports that individuals with SARS-CoV-2 in exhaled aerosols are more likely to transmit covid-19.
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| 29. |
- Alsved, Malin, et al.
(författare)
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Size distribution of exhaled aerosol particles containing SARS-CoV-2 RNA
- 2023
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Ingår i: Infectious Diseases. - : Informa UK Limited. - 2374-4235 .- 2374-4243. ; 55:2, s. 158-163
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Tidskriftsartikel (refereegranskat)abstract
- Background: SARS-CoV-2 in exhaled aerosols is considered an important contributor to the spread of COVID-19. However, characterizing the size distribution of virus-containing aerosol particles has been challenging as high concentrations of SARS-CoV-2 in exhaled air is mainly present close to symptom onset. We present a case study of a person with COVID-19 who was able to participate in extensive measurements of exhaled aerosols already on the day of symptom onset and then for the following three days. Methods: Aerosol collection was performed using an eight-stage impactor while the subject was breathing, talking and singing, for 30 min each, once every day. In addition, nasopharyngeal samples, saliva samples, room air samples and information on symptom manifestations were collected every day. Samples were analyzed by RT-qPCR for detection of SARS-CoV-2 RNA. Results: SARS-CoV-2 RNA was detected in seven of the eight particle size fractions, from 0.34 to >8.1 µm, with the highest concentrations found in 0.94–2.8 µm particles. The concentration of SARS-CoV-2 RNA was highest on the day of symptom onset, and declined for each day thereafter. Conclusion: Our data showed that 90% of the exhaled SARS-CoV-2 RNA was found in aerosol particles <4.5 µm, indicating the importance of small particles for the transmission of COVID-19 close to symptom onset. These results are important for our understanding of airborne transmission, for developing accurate models and for selecting appropriate mitigation strategies.
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| 30. |
- 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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| 31. |
- 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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| 32. |
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| 33. |
- Hussein, Tareq, et al.
(författare)
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Indoor model simulation for covid-19 transport and exposure
- 2021
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 18:6
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Tidskriftsartikel (refereegranskat)abstract
- Transmission of respiratory viruses is a complex process involving emission, deposition in the airways, and infection. Inhalation is often the most relevant transmission mode in indoor environments. For severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the risk of inhalation transmission is not yet fully understood. Here, we used an indoor aerosol model combined with a regional inhaled deposited dose model to examine the indoor transport of aerosols from an infected person with novel coronavirus disease (COVID-19) to a susceptible person and assess the potential inhaled dose rate of particles. Two scenarios with different ventilation rates were compared, as well as adult female versus male recipients. Assuming a source strength of 10 viruses/s, in a tightly closed room with poor ventilation (0.5 h−1 ), the respiratory tract deposited dose rate was 140–350 and 100–260 inhaled viruses/hour for males and females; respectively. With ventilation at 3 h−1 the dose rate was only 30–90 viruses/hour. Correcting for the half-life of SARS-CoV-2 in air, these numbers are reduced by a factor of 1.2–2.2 for poorly ventilated rooms and 1.1–1.4 for well-ventilated rooms. Combined with future determinations of virus emission rates, the size distribution of aerosols containing the virus, and the infectious dose, these results could play an important role in understanding the full picture of potential inhalation transmission in indoor environments.
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| 34. |
- Ladhani, Laila, et al.
(författare)
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Efficient electrostatic sampling of aerosols into liquid
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Despite an increasing demand for the identification and quantification of airborne pathogens, there is an unmet need for point-of-care instruments that provide both capture and analysis of bioaerosols. The integration of electrostatic precipitation of aerosol particles directly into liquid with lab-on-a-chip-based biomolecular analysis has been previously suggested as a promising solution for this purpose.This work investigates liquid collector designs for such instruments. We hypothesize that the geometry of the collector; and the position of its air-liquid interface with respect to the electrostatic field and aerosol flow, can be optimized for a maximum sample concentration.We designed four liquid collectors with a small form factor, adapted for concatenating point-to-plane electrostatic precipitators with integrated downstream analysis. The collectors were evaluated for their absolute mass collection and their sample concentration, by sampling radioactive aerosol and color dye aerosol. Collectors with their air-liquid surface parallel to the charged aerosol flow performed significantly better than those shaped as a cup with an air-liquid surface perpendicular to the flow. Whereas the electrostatic precipitators with the best performing collector designs captured only 32% of the aerosol mass compared to a commercial impinger, their resulting sample concentration was 4 times higher.
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| 35. |
- Löndahl, Jakob, et al.
(författare)
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Abrupt decreases in infectivity of SARS-CoV-2 in aerosols
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424. ; 119:29
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Tidskriftsartikel (refereegranskat)abstract
- A respiratory virus emitted in an aerosol particle will experience a tough journey with many obstacles before finding a new host where it can cause an infection (Fig. 1). By every second, its chances to replicate decrease due to removal by building ventilation, deposition on surfaces, or loss in infectivity. Thus, the transport of infectious viruses from the exhaled breath of one person to the inhaled air of another typically occurs within a few minutes. During this short time, the aerosol will undergo several transformations because of changing environmental conditions. Nevertheless, due to methodological challenges, we still have a remarkably limited understanding of the relationships between environmental factors and survival of pathogens in aerosols on short timescales. In a study in PNAS, Oswin et al. (1) show that the infectivity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can decrease abruptly when aerosol particles move between environments.
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| 36. |
- Löndahl, Jakob, et al.
(författare)
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Luftvägsvirus vid arbetsplatser - Smittvägar, riskfaktorer och skyddsåtgärder
- 2021
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Ingår i: Arbete och hälsa. - 0346-7821. ; 55:2, s. 1-53
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Tidskriftsartikel (refereegranskat)abstract
- Att spridning av sjukdomsframkallande luftvägsvirus kostar samhället enorma resurser har blivit uppenbart för alla under covid-19, men ovälkomna virus har varit människans följeslagare genom hela historien och ständigt uppkommer nya varianter med särskilt hög smittsamhet eller dödlighet. Riskerna har ökat med befolkningstillväxt och globalisering. Samtidigt har våra förutsättningar att skydda oss också har blivit bättre genom ökad kunskap och framsteg inom medicin och teknik.Syftet med denna kunskapssammanställning är att beskriva smittvägar, riskfaktorer och skyddsåtgärder för infektiös luftvägssjukdom och därmed bidra till en minskad smittrisk vid arbetsplatser. Mycket av innehållet bygger på forskning om influensa och covid-19, men även en rad andra luftvägsinfektioner är inkluderade.Spridning av virus har här delats upp i tre smittvägar: inandning, direkt deponering och kontakt. Risken för smitta via inandning av virus är särskilt stor när avstånden mellan människor är korta och uppehållstiden lång i lokaler med dålig ventilation. Risken ökar om det också pågår aktiviteter som innebär spridning av virusinnehållande aerosolpartiklar till luften, såsom högt tal eller sång eller vissa medicinska procedurer, eller om den inandade luftmängden är förhöjd, som vid tungt arbete. Virusöverföring via direkt deponering sker när stora smittbärande droppar stänker direkt på en mottagare vid exempelvis hosta. Virusspridning via både inandning och direkt deponering sker på olika sätt genom luften, men benämns här inte ”luftsmitta” eftersom detta begrepp åtminstone enligt klassisk medicinsk indelning syftat på (effektiv) smitta via inandning över avstånd mer än enstaka meter och eftersom det främst använts för sjukdomar som är mycket allvarliga och därför kräver extrema skyddsåtgärder. Smitta via kontakt kan ske antingen via direkt beröring eller genom mellanled, som handtag eller andra ytor.Samtliga tre smittvägar är välbelagda för luftvägsvirus i den vetenskapliga litteraturen, men deras relativa betydelse varierar beroende situation, virustyp och interventioner för att minska smitta. För covid-19 pekar mycket forskning mot att inandning är en dominerande smittväg i många miljöer. Vissa yrkesgrupper, särskilt inom vårdsektorn, löper en förhöjd risk att smittas av luftvägsvirus.En lång rad skyddsåtgärder finns tillgängliga för att på olika sätt minska smittrisker: distans, hygien, fysiska barriärer, ventilation, administrativa åtgärder (exempelvis information, regleringar, kontroller, checklistor) och personlig skyddsutrustning. De flesta av dessa åtgärder har starkt stöd av vetenskapliga studier.
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- Petersson Sjögren, Madeleine, et al.
(författare)
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Measurement report : Atmospheric fluorescent bioaerosol concentrations measured during 18 months in a coniferous forest in the south of Sweden
- 2023
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Ingår i: Atmospheric Chemistry and Physics. - 1680-7316. ; 23:9, s. 4977-4992
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Tidskriftsartikel (refereegranskat)abstract
- Biological aerosol particles affect human health, are essential for microbial and gene dispersal, and have been proposed as important agents for atmospheric processes. However, the abundance and size distributions of atmospheric biological particles are largely unknown. In this study we used a laser-induced fluorescence instrument to measure fluorescent biological aerosol particle (FBAP) concentrations for 18 months (October 2020-April 2022) at a rural, forested site in Sweden. The aim of this study was to investigate FBAP number concentrations (NFBAP) over time and analyze their relationship with meteorological parameters. NFBAP was highest in summer and lowest in winter, exhibiting a g1/4g5-fold difference between these seasons. The median NFBAP was 0.0050, 0.0025, 0.0027, and 0.0126gcm-3 in fall, winter, spring, and summer, respectively, and constituted g1/4g0.1-0.5g% of the total supermicron particle number concentration. NFBAP was dominated by the smallest measured size fraction (1-3gμm), suggesting that the main portions of the biological particles measured were due to single bacterial cells, fungal spores, and bacterial agglomerates. NFBAP was significantly correlated with increasing air temperature (P<0.01) in all seasons. For most of the campaign NFBAP was seen to increase with wind speed (P<0.01), while the relationship with relative humidity was for most of the campaign nonsignificant (46g%) but for a large part (30g%) negative (P<0.05). Our results indicate that NFBAP was highest during warm and dry conditions when wind speeds were high, suggesting that a major part of the FBAP in spring and summer was due to mechanical aerosol generation and release mechanisms. In fall, relative humidity may have been a more important factor in bioaerosol release. This is one of the longest time series of atmospheric FBAPs, which are greatly needed for estimates of bioaerosol background concentrations in comparable regions.
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- Thuresson, Sara, et al.
(författare)
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Airborne SARS-CoV-2 during childbirth
- 2023
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Konferensbidrag (refereegranskat)abstract
- Airborne SARS CoV 2 is considered to play a major role in covid 19 transmission, and has been found in several hospital environments. There is a need to investigate the presence of airborne SARS CoV 2 in other hospital areas than traditional infectious disease wards. The results from the present study can contribute to a better understanding of the risk of covid 19 transmission by aerosols at delivery wards.
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- Thuresson, Sara, et al.
(författare)
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Airborne SARS-CoV-2 RNA collected during childbirth and autopsy
- 2023
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Konferensbidrag (refereegranskat)abstract
- Airborne SARS-CoV-2 is considered to play a major role in covid-19 transmission, and several studies have reported its presence in hospital environments, including corridors, patient rooms, cohort rooms and ICUs (Dinoi et al., 2022). The risk of airborne virus have been associated with a number of factors, such as low ventilation, high patient viral load and in some cases, certain medical procedures.However, specific medical situations still deserve further investigation. One such situation of interest is childbirth, as respiratory emissions, which could contain virus, are increased due to heavy breathing during labor. Another situation with potential risk for airborne SARS-CoV-2 is autopsy.The aim of the current study was to further explore the presence of airborne SARS-CoV-2 RNA during childbirth and autopsy.The results in this study can increase our understanding about the risk of covid-19 transmission by aerosols at delivery wards and during autopsy, even though the sample material is small. Reports of airborne SARS-CoV-2 in hospital environments contribute to improving guidelines for protective equipment for healthcare personnel working with such patients.
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| 46. |
- Thuresson, Sara, et al.
(författare)
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Airborne Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) in Hospitals : Effects of Aerosol-Generating Procedures, HEPA-Filtration Units, Patient Viral Load, and Physical Distance
- 2022
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Ingår i: Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. - : Oxford University Press (OUP). - 1537-6591. ; 75:1, s. 89-96
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Transmission of coronavirus disease 2019 (COVID-19) can occur through inhalation of fine droplets or aerosols containing infectious virus. The objective of this study was to identify situations, patient characteristics, environmental parameters, and aerosol-generating procedures (AGPs) associated with airborne severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus.METHODS: Air samples were collected near hospitalized COVID-19 patients and analyzed by RT-qPCR. Results were related to distance to the patient, most recent patient diagnostic PCR cycle threshold (Ct) value, room ventilation, and ongoing potential AGPs.RESULTS: In total, 310 air samples were collected; of these, 26 (8%) were positive for SARS-CoV-2. Of the 231 samples from patient rooms, 22 (10%) were positive for SARS-CoV-2. Positive air samples were associated with a low patient Ct value (OR, 5.0 for Ct <25 vs >25; P = .01; 95% CI: 1.18-29.5) and a shorter physical distance to the patient (OR, 2.0 for every meter closer to the patient; P = .05; 95% CI: 1.0-3.8). A mobile HEPA-filtration unit in the room decreased the proportion of positive samples (OR, .3; P = .02; 95% CI: .12-.98). No association was observed between SARS-CoV-2-positive air samples and mechanical ventilation, high-flow nasal cannula, nebulizer treatment, or noninvasive ventilation. An association was found with positive expiratory pressure training (P < .01) and a trend towards an association for airway manipulation, including bronchoscopies and in- and extubations.CONCLUSIONS: Our results show that major risk factors for airborne SARS-CoV-2 include short physical distance, high patient viral load, and poor room ventilation. AGPs, as traditionally defined, seem to be of secondary importance.
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| 47. |
- Thuresson, Sara, et al.
(författare)
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Characteristics of SARS-CoV-2-containing aerosols in hospital corridors
- 2022
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Ingår i: ; , s. 1-1
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Konferensbidrag (refereegranskat)abstract
- The aim of this work is to investigate the presence of airborne SARS-CoV-2 in corridors of infection wards, and gain more detailed size information of SARS-CoV-2-containing aerosols. Associations between SARS-CoV-2 presence and relative humidity and/or temperature in the facilities is also explored.
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