| 1. |
- Alsved, Malin, et al.
(author)
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Sources of Airborne Norovirus in Hospital Outbreaks
- 2020
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In: Clinical Infectious Diseases. - : Oxford University Press (OUP). - 1537-6591 .- 1058-4838. ; 70:10, s. 2023-2028
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Journal article (peer-reviewed)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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| 2. |
- Alsved, Malin, et al.
(author)
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Aerosolization and recovery of viable murine norovirus in an experimental setup
- 2020
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In: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Journal article (peer-reviewed)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.
(author)
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Droplet, aerosol and SARS-CoV-2 emissions during singing and talking
- 2021
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Conference paper (peer-reviewed)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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| 6. |
- Alsved, Malin, et al.
(author)
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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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Conference paper (peer-reviewed)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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| 7. |
- Alsved, Malin, et al.
(author)
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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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Conference paper (peer-reviewed)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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| 8. |
- Niehoff, Nicole M., et al.
(author)
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Prediagnostic serum polychlorinated biphenyl concentrations and primary liver cancer : A case-control study nested within two prospective cohorts
- 2020
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In: Environmental Research. - : Elsevier BV. - 0013-9351. ; 187
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Journal article (peer-reviewed)abstract
- Background: Polychlorinated biphenyls (PCBs) were used in electrical equipment and a range of construction materials. Although banned in the United States and most of Europe in the 1970s, they are highly persistent in the environment and bioaccumulate. Whether PCBs are associated with liver cancer risk at general population levels is unknown. Methods: This study consisted of 136 incident liver cancer cases and 408 matched controls from the Kaiser Permanente Northern California Multiphasic Health Checkup (MHC) cohort and 84 cases and 252 matched controls from the Norwegian Janus cohort. Sera collected in the 1960s–1980s were measured for 37 PCB congeners and markers of hepatitis B (HBV) and C (HCV) infection. Odds ratios (OR) and 95% confidence intervals (CI) for tertiles of each lipid-adjusted PCB were estimated from conditional logistic regression. We also examined the molar sum of congeners in groups: total PCBs; low, medium, and high chlorination; and Wolff functional groups. Results: Concentrations of individual congeners from the 1960s/1970s sera ranged from 1.3-123.0 and 1.4–116.0 ng/g lipid among MHC cases and controls, respectively, and from 1.9-258.0 and 1.9–271.0 ng/g lipid among Janus cases and controls, respectively. Among MHC participants with sera from the 1960s, collected an average of 27 years before diagnosis among cases, the top tertile of PCBs 151, 170, 172, 177, 178, 180, and 195 was significantly associated with elevated odds of liver cancer (OR range = 2.01–2.38); most of these congeners demonstrated exposure-response trends. For example, ORtertile 3vs1 = 2.38 (95% CI: 1.22–4.64, p-trend = 0.01) for PCB 180. As a group, Wolff group 1b congeners, which are biologically persistent and weak phenobarbital inducers, were associated with increased odds. In MHC participants, ever vs. never HBV or HCV infection modified the PCB-liver cancer associations. There was little evidence of an association between PCBs and odds of liver cancer among the Janus cohort. Discussion: We observed associations between a number of PCB congeners and increased odds of liver cancer among MHC, but not Janus, participants with sera from the 1960s/1970s.
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| 10. |
- Thuresson, Sara, et al.
(author)
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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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In: 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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Journal article (peer-reviewed)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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| 15. |
- Waldenström, Jesper, 1985, et al.
(author)
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Absence of interferon-lambda 4 enhances spontaneous clearance of acute hepatitis C virus genotypes 1-3 infection
- 2021
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In: Scandinavian Journal of Gastroenterology. - : Informa UK Limited. - 0036-5521 .- 1502-7708. ; 56:7
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Journal article (peer-reviewed)abstract
- Objectives Absence of a functional interferon-lambda 4 (IFN-lambda 4) gene (IFNL4) predicts spontaneous resolution of acute hepatitis C virus (HCV) infections in regions with a predominance of genotype 1, whereas variants of the inosine triphosphate pyrophosphatase (ITPase) gene (ITPA) entailing reduced activity associate with increased sustained virologic response rates following some therapeutic regimens. This study aimed at investigating the impact of IFNL4 on acute HCV genotype 2 or 3 infections, and whether ITPase activity influenced outcome. Materials and Methods Two hundred and seven people who injected drugs (PWID) with documented anti-HCV seroconversion, and 57 PWID with reinfection with HCV were analyzed regarding IFNL4 (rs368234815 and rs12979860) and ITPA (rs1127354 and rs7270101), and longitudinally followed regarding HCV RNA. Results The spontaneous clearance of HCV infection in anti-HCV seronegative PWID was enhanced when IFN-lambda 4 was absent (44% vs. 20% for IFNL4 TT/TTrs1368234815 and Delta G(rs1368234815) respectively, p < .001; OR 3.2) across genotypes 1-3. The proportion lacking IFN-lambda 4 was further increased following resolution of repeated re-exposure to HCV (74% among re-infected participants who had cleared at least two documented HCV infections). ITPA genetic variants did not independently impact on the outcome, but among males lacking IFN-lambda 4, reduced ITPase activity markedly augmented the likelihood of resolution (65% vs. 29% for <100% and 100% ITPase activity, p = .006). Conclusions Absence of IFN-lambda 4 entails an enhanced likelihood of spontaneous resolution both following primary acute infection and repeated re-exposure to HCV across genotypes 1-3. Among men lacking IFN-lambda 4, reduced ITPase activity improved outcome.
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