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Papers by Kwok wai Tham
Building and Environment, 2018
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arXiv (Cornell University), Sep 28, 2020
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We conducted a prospective environmental surveillance study to investigate the air, surface, dust... more We conducted a prospective environmental surveillance study to investigate the air, surface, dust and water contamination of a room occupied by a patient infected with Monkeypox virus (MPXV) at various stages of his illness. The patient tested positive for MPXV from a throat swab and skin lesions. Environmental sampling was conducted in a negative pressure room with 12 unidirectional HEPA air changes per hour and daily cleaning of the surfaces. A total of 179 environmental samples were collected on days 7, 8, 13, and 21 of his illness. Air, surface, and dust contamination was highest during the first eight days of the illness, with a gradual decline to the lowest contamination level by day 21. Viable MPXV was isolated from surfaces and dust samples and no viable virus was isolated from the air and water samples.SynopsisInadequate research prevail on the mode of transmission for monkeypox virus. This study reports the findings of viable monkeypox virus from the patient environment, h...
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Data on the viral loads in respiratory aerosols from patients infected with Delta and Omicron var... more Data on the viral loads in respiratory aerosols from patients infected with Delta and Omicron variants are limited. In this study, we used an exhaled breath bioaerosol collector to collect aerosol samples in coarse (> 5µm) and fine (≤ 5µm) fractions from COVID-19 patients infected with these VOCs while doing various respiratory activities. Samples were tested via SARS-CoV-2 RT-qPCR and virus culture. Nine patients (4 Delta and 5 Omicron) were included. Viral RNA was detectable in seven participants, with greater viral loads in fine aerosols. Notably SARS-CoV-2 RNA was consistently detectable in respiratory samples of all Omicron patients despite them being fully vaccinated and mostly asymptomatic in contrast with Delta patients. Singing and talking without mask generated the greatest viral loads underscoring the transmission potential of SARS-CoV-2 and its variants via respiratory aerosols. The more consistent detection of viral RNA in Omicron-infected patients may account for it...
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BackgroundMultiple SARS-CoV-2 superspreading events suggest that aerosols play an important role ... more BackgroundMultiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. However, the detailed roles of coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing are not well-understood.MethodsUsing a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing.ResultsAmong the 22 study participants, 13 (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic patients and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per patient. Patients earlier in illness were more likely to emit detectable RNA, and loads differed significantly between breathing, talking, and singing. The largest proportion of SARS-CoV-2 RNA copies was emitted by singing (53%), follow...
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International Journal of Infectious Diseases, 2018
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Building and Environment, 2018
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Epidemiology, 2007
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Note: EPFL Reference LESO-PB-CONF-2003-002 Record created on 2005-01-12, modified on 2016-08-08
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Habitat International, 1997
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Environment International, 2004
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Energies, 2013
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Building and Environment, 2002
Most indoor air quality (IAQ) investigations take an air handling unit (AHU) - based zone as the ... more Most indoor air quality (IAQ) investigations take an air handling unit (AHU) - based zone as the basic unit for investigation from the logical viewpoint that the AHU constitutes the mechanism for mixing and (cross-) transportation of pollutants within the zone. If there is very good air-mixing, as indicated by a high air exchange effectiveness, the single zone approach may
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Building and Environment, 2006
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Building and Environment, 2006
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Building and Environment, 2007
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Indoor Air, Nov 24, 2003
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Building and Environment, 2018
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arXiv (Cornell University), Sep 28, 2020
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We conducted a prospective environmental surveillance study to investigate the air, surface, dust... more We conducted a prospective environmental surveillance study to investigate the air, surface, dust and water contamination of a room occupied by a patient infected with Monkeypox virus (MPXV) at various stages of his illness. The patient tested positive for MPXV from a throat swab and skin lesions. Environmental sampling was conducted in a negative pressure room with 12 unidirectional HEPA air changes per hour and daily cleaning of the surfaces. A total of 179 environmental samples were collected on days 7, 8, 13, and 21 of his illness. Air, surface, and dust contamination was highest during the first eight days of the illness, with a gradual decline to the lowest contamination level by day 21. Viable MPXV was isolated from surfaces and dust samples and no viable virus was isolated from the air and water samples.SynopsisInadequate research prevail on the mode of transmission for monkeypox virus. This study reports the findings of viable monkeypox virus from the patient environment, h...
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Data on the viral loads in respiratory aerosols from patients infected with Delta and Omicron var... more Data on the viral loads in respiratory aerosols from patients infected with Delta and Omicron variants are limited. In this study, we used an exhaled breath bioaerosol collector to collect aerosol samples in coarse (> 5µm) and fine (≤ 5µm) fractions from COVID-19 patients infected with these VOCs while doing various respiratory activities. Samples were tested via SARS-CoV-2 RT-qPCR and virus culture. Nine patients (4 Delta and 5 Omicron) were included. Viral RNA was detectable in seven participants, with greater viral loads in fine aerosols. Notably SARS-CoV-2 RNA was consistently detectable in respiratory samples of all Omicron patients despite them being fully vaccinated and mostly asymptomatic in contrast with Delta patients. Singing and talking without mask generated the greatest viral loads underscoring the transmission potential of SARS-CoV-2 and its variants via respiratory aerosols. The more consistent detection of viral RNA in Omicron-infected patients may account for it...
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Bookmarks Related papers MentionsView impact
BackgroundMultiple SARS-CoV-2 superspreading events suggest that aerosols play an important role ... more BackgroundMultiple SARS-CoV-2 superspreading events suggest that aerosols play an important role in driving the COVID-19 pandemic. However, the detailed roles of coarse (>5μm) and fine (≤5μm) respiratory aerosols produced when breathing, talking, and singing are not well-understood.MethodsUsing a G-II exhaled breath collector, we measured viral RNA in coarse and fine respiratory aerosols emitted by COVID-19 patients during 30 minutes of breathing, 15 minutes of talking, and 15 minutes of singing.ResultsAmong the 22 study participants, 13 (59%) emitted detectable levels of SARS-CoV-2 RNA in respiratory aerosols, including 3 asymptomatic patients and 1 presymptomatic patient. Viral loads ranged from 63–5,821 N gene copies per expiratory activity per patient. Patients earlier in illness were more likely to emit detectable RNA, and loads differed significantly between breathing, talking, and singing. The largest proportion of SARS-CoV-2 RNA copies was emitted by singing (53%), follow...
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International Journal of Infectious Diseases, 2018
Bookmarks Related papers MentionsView impact
Building and Environment, 2018
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Epidemiology, 2007
Bookmarks Related papers MentionsView impact
Note: EPFL Reference LESO-PB-CONF-2003-002 Record created on 2005-01-12, modified on 2016-08-08
Bookmarks Related papers MentionsView impact
Habitat International, 1997
Bookmarks Related papers MentionsView impact
Environment International, 2004
Bookmarks Related papers MentionsView impact
Energies, 2013
Bookmarks Related papers MentionsView impact
Building and Environment, 2002
Most indoor air quality (IAQ) investigations take an air handling unit (AHU) - based zone as the ... more Most indoor air quality (IAQ) investigations take an air handling unit (AHU) - based zone as the basic unit for investigation from the logical viewpoint that the AHU constitutes the mechanism for mixing and (cross-) transportation of pollutants within the zone. If there is very good air-mixing, as indicated by a high air exchange effectiveness, the single zone approach may
Bookmarks Related papers MentionsView impact
Building and Environment, 2006
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Building and Environment, 2006
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Building and Environment, 2007
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Indoor Air, Nov 24, 2003
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