Publications

Epidemiological, Clinical, and Phylogenetic Characteristics of the First SARS-CoV-2 Transmission in a Nursing Home of Singapore: A Prospective Observational Investigation

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission has resulted in a significant burden among nursing home facilities globally. This prospective observational cohort study aims to define the potential sources of introduction and characteristics of SARS-CoV-2 transmission of the first nursing home facility in Singapore. An epidemiological serial point-prevalence survey of SARS-CoV-2 was conducted among 108 residents and 56 healthcare staff (HCS). In the current study, 14 (13%) residents and two (3.6%) HCS were diagnosed with coronavirus disease 2019 (COVID-19), with a case fatality rate (CFR) of 28.6% (4/14) among the residents. The median age of the infected residents was 86.5 [interquartile range (IQR) 78.5-88] and 85.7% were women. Five residents were symptomatic (35.7%) and the others were asymptomatic (64.3%). A higher proportion of residents who succumbed to COVID-19 had hypertension than those who recovered. The SARS-CoV-2 whole-genome sequencing showed lineage B.6 which is rare globally but common regionally during the early phase of the pandemic. Household transmission is a potential source of introduction into the nursing home, with at least six epidemiologically linked secondary cases. Male residents were less implicated due to the staff segregation plan by block. Among residents, a higher proportion of the non-survivors were asymptomatic and had hypertension compared with survivors.

Citation: Pang J, Tan HN, Mak TM, Octavia S, Maurer-Stroh S, Sirota FL, Chan MPC, Leong IYO, Koh VTJ, Ooi PL, Vasoo S, Fisher D, Cui L, Rafman H, Cutter J, Lee VJ. Epidemiological, Clinical, and Phylogenetic Characteristics of the First SARS-CoV-2 Transmission in a Nursing Home of Singapore: A Prospective Observational Investigation. Front Med (Lausanne). 2022 Jan 28;8:790177. doi: 10.3389/fmed.2021.790177. PMID: 35155470; PMCID: PMC8831716.

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Risk Factors of Septic Metastatic Infection among Patients with Klebsiella pneumoniae Liver Abscess in Singapore: A Case-Control Study

Abstract

Metastatic infection resulting from Klebsiella pneumoniae liver abscess (KPLA) results in high mortality and morbidity. This study aimed to determine the risk factors associated with metastatic infection among patients with KPLA in Singapore. A retrospective case-control analysis among adult patients admitted to the National University Hospital with KPLA between 2013 and 2017 was conducted. Univariate and multivariate regression analysis was conducted. Of the 116 KPLA patients, 38.8% had pulmonary metastatic infection. Length of hospital stay (P = 0.001) and intensive care unit admissions (P = 0.044) were significantly longer and greater, respectively, among the patients with metastatic infection. Sepsis-induced hypotension (adjusted odds ratio [AOR], 4.88; 95% CI, 1.1-21.69), breathlessness (AOR, 5.10; 95% CI, 1.42-18.27), and abscess size (AOR, 1.02; 95% CI, 1.01-1.03) were associated independently with septic metastatic infection. Patients with KPLA who had breathlessness and larger abscess size are at a greater risk of septic metastatic infection.

Citation: Mukherjee S, Archuleta S, Pang J. Risk Factors of Septic Metastatic Infection among Patients with Klebsiella pneumoniae Liver Abscess in Singapore: A Case-Control Study. Am J Trop Med Hyg. 2022 Jan 24:tpmd210623. doi: 10.4269/ajtmh.21-0623. Epub ahead of print. PMID: 35073511.

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Weather Factors Associated with Reduced Risk of Dengue Transmission in an Urbanized Tropical City

Abstract

This study assessed the impact of weather factors, including novel predictors-pollutant standards index (PSI) and wind speed-on dengue incidence in Singapore between 2012 and 2019. Autoregressive integrated moving average (ARIMA) model was fitted to explore the autocorrelation in time series and quasi-Poisson model with a distributed lag non-linear term (DLNM) was set up to assess any non-linear association between climatic factors and dengue incidence. In DLNM, a PSI level of up to 111 was positively associated with dengue incidence; incidence reduced as PSI level increased to 160. A slight rainfall increase of up to 7 mm per week gave rise to higher dengue risk. On the contrary, heavier rainfall was protective against dengue. An increase in mean temperature under around 28.0 °C corresponded with increased dengue cases whereas the association became negative beyond 28.0 °C; the minimum temperature was significantly positively associated with dengue incidence at around 23-25 °C, and the relationship reversed when temperature exceed 27 °C. An overall positive association, albeit insignificant, was observed between maximum temperature and dengue incidence. Wind speed was associated with decreasing relative risk (RR). Beyond prevailing conclusions on temperature, this study observed that extremely poor air quality, high wind speed, minimum temperature ≥27 °C, and rainfall volume beyond 12 mm per week reduced the risk of dengue transmission in an urbanized tropical environment.

Citation: Gui H, Gwee S, Koh J, Pang J. Weather Factors Associated with Reduced Risk of Dengue Transmission in an Urbanized Tropical City. Int J Environ Res Public Health. 2021 Dec 29;19(1):339. doi: 10.3390/ijerph19010339. PMID: 35010600; PMCID: PMC8751148.

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Association between pet ownership and physical activity and mental health during the COVID-19 “circuit breaker” in Singapore

Abstract

Introduction: The negative impact of the coronavirus disease 2019 (COVID-19) pandemic on mental health and physical activity is well reported. While prior studies showed a positive influence of pet ownership on physical activity and mental health, the interactions between the pandemic and pet ownership are not well studied.

Objective: To determine the association between pet ownership, physical activity levels and mental health during the COVID-19 pandemic.

Materials and methods: A cross-sectional study was conducted from May 19 to July 13, 2020 among Singapore residents aged 21 to 64 years through a previously published questionnaire. Inverse probability treatment weighting was used to develop mixed-effects models for outcome comparisons. We recorded participant data on pet ownership, duration and intensity of physical activity, and RAND 36-item Health Survey mental health domains during the COVID-19 pandemic.

Results: The questionnaire was completed by 431 pet owners and 103 non-pet owners. A greater proportion of pet owners were female, non-married, employed and owned pets in the past. Pet owners reported 31.8 (95% CI 13.6 to 50; p = .001) more minutes per week of mild-intensity physical activity compared to non-pet owners. No statistically significant differences were found for moderate- and vigorous-intensity physical activity. Pet owners had better emotional well-being ( = 9.66, 95% CI 4.97 to 14.4; p < .001), energy ( = 8.29, 95% CI 3.46 to 13.1; p = .001) and social functioning ( = 11.2, 95% CI 5.03 to 17.4; p < .001) scores than non-pet owners. However, no statistically significant difference was observed for general health scores. Pet owner physical activity levels, general health, emotional well-being and energy scores correlated positively with pet attachment scores.

Conclusion: Pet ownership was associated with greater physical activity levels and better mental health, particularly in main caregivers with higher pet attachment scores. These findings suggest that pet ownership is beneficial to physical and mental well-being during periods of social isolation amidst a global pandemic.

Citation: Tan JSQ, Fung W, Tan BSW, Low JY, Syn NL, Goh YX, Pang J. Association between pet ownership and physical activity and mental health during the COVID-19 “circuit breaker” in Singapore. One Health. 2021 Nov 3;13:100343. doi: 10.1016/j.onehlt.2021.100343. PMID: 34805473; PMCID: PMC8581575.

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Global dengue importation: a systematic review

Abstract

Background: Importation of dengue following globalization presents an emerging threat to global health. However, evidence on global geographical sources and the potential of dengue importation globally are lacking. This study aims to systematically review the sources of dengue importation globally and the risk of dengue outbreaks globally.

Methods: This systematic review was conducted in accordance to Cochrane’s PRISMA guidelines. Articles published through 31 December 2019 with laboratory-confirmed dengue imported cases were consolidated from PubMed, EMBASE and Scopus. Sources of dengue importation reported worldwide were analysed by country and geographical regions. Sources of dengue importation into United States of America and Europe specifically were also analysed.

Results: A total of 3762 articles were found. Among which, 210 articles—documenting 14,972 imported dengue cases with reported sources—were eligible. 76.3% of imported cases worldwide were from Asia. 15.7%, 5.6%, 2.0% and 0.1% were imported from the Americas, Africa, Oceania and Europe regions respectively. Imported dengue cases in the U.S. were from Americas (55.3%), Asia (34.7%), Africa (6.7%) and Oceania (3.3%). Imported dengue cases in Europe were from Asia (66.0%), Americas (21.9%), Africa (10.8%) and Oceania (1.1%).

Conclusion: The potential of dengue outbreaks occurring globally, especially among non-endemic regions with dengue-susceptible populations is high. With the expansion of Aedes mosquito population globally due to global warming and globalisation, dengue importation constitutes an emerging global health security threat.

Citation: Gwee, X.W.S., Chua, P.E.Y. & Pang, J. Global dengue importation: a systematic review. BMC Infect Dis 21, 1078 (2021). https://doi.org/10.1186/s12879-021-06740-1

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Wastewater surveillance to infer COVID-19 transmission: A systematic review

Abstract

Successful detection of SARS-COV-2 in wastewater suggests the potential utility of wastewater-based epidemiology (WBE) for COVID-19 community surveillance. This systematic review aims to assess the performance of wastewater surveillance as early warning system of COVID-19 community transmission. A systematic search was conducted in PubMed, Medline, Embase and the WBE Consortium Registry according to PRISMA guidelines for relevant articles published until 31st July 2021. Relevant data were extracted and summarized. Quality of each paper was assessed using an assessment tool adapted from Bilotta et al.’s tool for environmental science. Of 763 studies identified, 92 studies distributed across 34 countries were shortlisted for qualitative synthesis. A total of 26,197 samples were collected between January 2020 and May 2021 from various locations serving population ranging from 321 to 11,400,000 inhabitants. Overall sample positivity was moderate at 29.2% in all examined settings with the spike (S) gene having maximum rate of positive detections and nucleocapsid (N) gene being the most targeted. Wastewater signals preceded confirmed cases by up to 63 days, with 13 studies reporting sample positivity before the first cases were detected in the community. At least 50 studies reported an association of viral load with community cases. While wastewater surveillance cannot replace large-scale diagnostic testing, it can complement clinical surveillance by providing early signs of potential transmission for more active public health responses. However, more studies using standardized and validated methods are required along with risk analysis and modelling to understand the dynamics of viral outbreaks.

Citation: Shah, S., Gwee, S., Ng, J., Lau, N., Koh, J., & Pang, J. (2022). Wastewater surveillance to infer COVID-19 transmission: A systematic review. The Science of the Total Environment804, 150060. https://doi.org/10.1016/j.scitotenv.2021.150060

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Factors influencing SARS-CoV-2 transmission and outbreak control measures in densely populated settings

Abstract

Starting with a handful of SARS-CoV-2 infections in dormitory residents in late March 2020, rapid transmission in their dense living environments ensued and by October 2020, more than 50,000 acute infections were identified across various dormitories in Singapore. The aim of the study is to identify combination of factors facilitating SARS-CoV-2 transmission and the impact of control measures in a dormitory through extensive epidemiological, serological and phylogenetic investigations, supported by simulation models. Our findings showed that asymptomatic cases and symptomatic cases who did not seek medical attention were major drivers of the outbreak. Furthermore, each resident had about 30 close contacts and each infected resident spread to 4.4 (IQR 3.5–5.3) others at the start of the outbreak. The final attack rate of the current outbreak was 76.2% (IQR 70.6–98.0%) and could be reduced by further 10% under a modified dormitory housing condition. These findings are important when designing living environments in a post COVID-19 future to reduce disease spread and facilitate rapid implementation of outbreak control measures.

Citation: Pung, R., Lin, B., Maurer-Stroh, S. et al. Factors influencing SARS-CoV-2 transmission and outbreak control measures in densely populated settings. Sci Rep 11, 15297 (2021). https://doi.org/10.1038/s41598-021-94463-3

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Impact of travel ban implementation on COVID-19 spread in Singapore, Taiwan, Hong Kong and South Korea during the early phase of the pandemic: a comparative study

Abstract

Background: The COVID-19 pandemic has elicited imposition of some form of travel restrictions by almost all countries in the world. Most restrictions currently persist, although some have been gradually eased. It remains unclear if the trade-off from the unprecedented disruption to air travel was well worth for pandemic containment.

Method: A comparative analysis was conducted on Singapore, Taiwan, Hong Kong and South Korea’s COVID-19 response. Data on COVID-19 cases, travel-related and community interventions, socio-economic profile were consolidated. Trends on imported and local cases were analyzed using computations of moving averages, rate of change, particularly in response to distinct waves of travel-related interventions due to the outbreak in China, South Korea, Iran & Italy, and Europe.

Results: South Korea’s travel restrictions were observed to be consistently more lagged in terms of timeliness and magnitude, with their first wave of travel restrictions on flights departing from China implemented 34 days after the outbreak in Wuhan, compared to 22–26 days taken by Singapore, Taiwan and Hong Kong. South Korea’s restrictions against all countries came after 91 days, compared to 78–80 days for the other three countries. The rate of change of imported cases fell by 1.08–1.43 across all four countries following the first wave of travel restrictions on departures from China, and by 0.22–0.52 in all countries except South Korea in the fifth wave against all international travellers. Delayed rate of change of local cases resulting from travel restrictions imposed by the four countries with intrinsic importation risk, were not observed.

Conclusions: Travel restriction was effective in preventing COVID-19 case importation in early outbreak phase, but may still be limited in preventing general local transmission. The impact of travel restrictions, regardless of promptness, in containing epidemics likely also depends on the effectiveness of local surveillance and non-pharmaceutical interventions concurrently implemented.

Citation: Gwee, S.X.W., Chua, P.E.Y., Wang, M.X. et al. Impact of travel ban implementation on COVID-19 spread in Singapore, Taiwan, Hong Kong and South Korea during the early phase of the pandemic: a comparative study. BMC Infect Dis 21, 799 (2021). https://doi.org/10.1186/s12879-021-06449-1

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Relationship between local weather, air pollution and hospital attendances for urticaria in children: Time stratified analysis of 12,002 cases

Citation: Choo KJL, Ho AFW, Gui H, Tay PJM, Lee HY, Koh MS, Earnest A, Pek PP, Liu N, Chong SL, Pang J, Ong MEH. Relationship between local weather, air pollution and hospital attendances for urticaria in children: Time stratified analysis of 12,002 cases. Clin Exp Allergy. 2021 Sep 22. doi: 10.1111/cea.14015. Epub ahead of print. PMID: 34549849.

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Factors associated with high compliance behaviour against COVID-19 in the early phase of pandemic: a cross-sectional study in 12 Asian countries

Abstract

Introduction: Regardless of having effective vaccines against COVID-19, containment measures such as enhanced physical distancing and good practice of personal hygiene remain the mainstay of controlling the COVID-19 pandemic. Countries across Asia have imposed these containment measures to varying extents. However, residents in different countries would have a differing degree of compliance to these containment measures potentially due to differences in the level of awareness and motivation in the early phase of pandemic.

Objectives: In our study, we aimed to describe and correlate the level of knowledge and attitude with the level of compliance with personal hygiene and physical distancing practices among Asian countries in the early phase of pandemic.

Methods: A multinational cross-sectional study was carried out using electronic surveys between May and June 2020 across 14 geographical areas. Subjects aged 21 years and above were invited to participate through social media, word of mouth and electronic mail.

Results: Among the 2574 responses obtained, 762 (29.6%) participants were from East Asia and 1812 (70.4%) were from Southeast Asia (SEA). A greater proportion of participants from SEA will practise physical distancing as long as it takes (72.8% vs 60.6%). Having safe distancing practices such as standing more than 1 or 2 m apart (AdjOR 5.09 95% CI (1.08 to 24.01)) or more than 3 or 4 m apart (AdjOR 7.05 95% CI (1.32 to 37.67)), wearing a mask when they had influenza-like symptoms before the COVID-19 pandemic, preferring online news channels such as online news websites/applications (AdjOR 1.73 95% CI (1.21 to 2.49)) and social media (AdjOR 1.68 95% CI (1.13 to 2.50) as sources of obtaining information about COVID-19 and high psychological well-being (AdjOR 1.39 95% CI (1.04 to 1.87)) were independent factors associated with high compliance.

Conclusions: We found factors associated with high compliance behaviour against COVID-19 in the early phase of pandemic and it will be useful to consider them in risk assessment, communication and pandemic preparedness.

Citation: Chua CEKew GSDemutska A, et al. Factors associated with high compliance behaviour against COVID-19 in the early phase of pandemic: a cross-sectional study in 12 Asian countries.

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