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Jang G, Kim J, Lee Y, Son C, Ko KT, Lee H. Analysis of the impact of COVID-19 variants and vaccination on the time-varying reproduction number: statistical methods. Front Public Health 2024; 12:1353441. [PMID: 39022412 PMCID: PMC11253806 DOI: 10.3389/fpubh.2024.1353441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2023] [Accepted: 06/07/2024] [Indexed: 07/20/2024] Open
Abstract
Introduction The COVID-19 pandemic has profoundly impacted global health systems, requiring the monitoring of infection waves and strategies to control transmission. Estimating the time-varying reproduction number is crucial for understanding the epidemic and guiding interventions. Methods Probability distributions of serial interval are estimated for Pre-Delta and Delta periods. We conducted a comparative analysis of time-varying reproduction numbers, taking into account population immunity and variant differences. We incorporated the regional heterogeneity and age distribution of the population, as well as the evolving variants and vaccination rates over time. COVID-19 transmission dynamics were analyzed with variants and vaccination. Results The reproduction number is computed with and without considering variant-based immunity. In addition, values of reproduction number significantly differed by variants, emphasizing immunity's importance. Enhanced vaccination efforts and stringent control measures were effective in reducing the transmission of the Delta variant. Conversely, Pre-Delta variant appeared less influenced by immunity levels, due to lower vaccination rates. Furthermore, during the Pre-Delta period, there was a significant difference between the region-specific and the non-region-specific reproduction numbers, with particularly distinct pattern differences observed in Gangwon, Gyeongbuk, and Jeju in Korea. Discussion This research elucidates the dynamics of COVID-19 transmission concerning the dominance of the Delta variant, the efficacy of vaccinations, and the influence of immunity levels. It highlights the necessity for targeted interventions and extensive vaccination coverage. This study makes a significant contribution to the understanding of disease transmission mechanisms and informs public health strategies.
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Affiliation(s)
- Geunsoo Jang
- Nonlinear Dynamics and Mathematical Application Center, Kyungpook National University, Daegu, Republic of Korea
| | - Jihyeon Kim
- Department of Statistics, Kyungpook National University, Daegu, Republic of Korea
| | - Yeonsu Lee
- Department of Statistics, Kyungpook National University, Daegu, Republic of Korea
| | - Changdae Son
- Department of Statistics, Kyungpook National University, Daegu, Republic of Korea
| | - Kyeong Tae Ko
- Department of Statistics, Kyungpook National University, Daegu, Republic of Korea
| | - Hyojung Lee
- Department of Statistics, Kyungpook National University, Daegu, Republic of Korea
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2
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Willem L, Abrams S, Franco N, Coletti P, Libin PJK, Wambua J, Couvreur S, André E, Wenseleers T, Mao Z, Torneri A, Faes C, Beutels P, Hens N. The impact of quality-adjusted life years on evaluating COVID-19 mitigation strategies: lessons from age-specific vaccination roll-out and variants of concern in Belgium (2020-2022). BMC Public Health 2024; 24:1171. [PMID: 38671366 PMCID: PMC11047051 DOI: 10.1186/s12889-024-18576-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
BACKGROUND When formulating and evaluating COVID-19 vaccination strategies, an emphasis has been placed on preventing severe disease that overburdens healthcare systems and leads to mortality. However, more conventional outcomes such as quality-adjusted life years (QALYs) and inequality indicators are warranted as additional information for policymakers. METHODS We adopted a mathematical transmission model to describe the infectious disease dynamics of SARS-COV-2, including disease mortality and morbidity, and to evaluate (non)pharmaceutical interventions. Therefore, we considered temporal immunity levels, together with the distinct transmissibility of variants of concern (VOCs) and their corresponding vaccine effectiveness. We included both general and age-specific characteristics related to SARS-CoV-2 vaccination. Our scenario study is informed by data from Belgium, focusing on the period from August 2021 until February 2022, when vaccination for children aged 5-11 years was initially not yet licensed and first booster doses were administered to adults. More specifically, we investigated the potential impact of an earlier vaccination programme for children and increased or reduced historical adult booster dose uptake. RESULTS Through simulations, we demonstrate that increasing vaccine uptake in children aged 5-11 years in August-September 2021 could have led to reduced disease incidence and ICU occupancy, which was an essential indicator for implementing non-pharmaceutical interventions and maintaining healthcare system functionality. However, an enhanced booster dose regimen for adults from November 2021 onward could have resulted in more substantial cumulative QALY gains, particularly through the prevention of elevated levels of infection and disease incidence associated with the emergence of Omicron VOC. In both scenarios, the need for non-pharmaceutical interventions could have decreased, potentially boosting economic activity and mental well-being. CONCLUSIONS When calculating the impact of measures to mitigate disease spread in terms of life years lost due to COVID-19 mortality, we highlight the impact of COVID-19 on the health-related quality of life of survivors. Our study underscores that disease-related morbidity could constitute a significant part of the overall health burden. Our quantitative findings depend on the specific setup of the interventions under review, which is open to debate or should be contextualised within future situations.
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Affiliation(s)
- Lander Willem
- Department of Family Medicine and Population Health, Antwerp, Belgium.
- Centre for Health Economic Research and Modelling Infectious Diseases, University of Antwerp, Antwerp, Belgium.
| | - Steven Abrams
- Department of Family Medicine and Population Health, Antwerp, Belgium
- Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Nicolas Franco
- Data Science Institute, Hasselt University, Hasselt, Belgium
- Namur Institute for Complex Systems (naXys) and Department of Mathematics, University of Namur, Namur, Belgium
| | - Pietro Coletti
- Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Pieter J K Libin
- Data Science Institute, Hasselt University, Hasselt, Belgium
- Artificial Intelligence Lab, Vrije Universiteit Brussel, Brussels, Belgium
- Rega Institute for Medical Research, Clinical and Epidemiological Virology, University of Leuven, Leuven, Belgium
| | - James Wambua
- Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Simon Couvreur
- Department of Epidemiology and public health, Sciensano, Brussel, Belgium
| | - Emmanuel André
- National Reference Centre for Respiratory Pathogens, University Hospitals Leuven, Leuven, Belgium
- Department of Microbiology, Immunology and Transplantation, University of Leuven, Leuven, Belgium
| | - Tom Wenseleers
- Laboratory of Socioecology and Social Evolution, University of Leuven, Leuven, Belgium
| | - Zhuxin Mao
- Centre for Health Economic Research and Modelling Infectious Diseases, University of Antwerp, Antwerp, Belgium
| | - Andrea Torneri
- Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Christel Faes
- Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Philippe Beutels
- Centre for Health Economic Research and Modelling Infectious Diseases, University of Antwerp, Antwerp, Belgium
- School of Public Health and Community Medicine, The University of New South Wales, Sydney, Australia
| | - Niel Hens
- Centre for Health Economic Research and Modelling Infectious Diseases, University of Antwerp, Antwerp, Belgium
- Data Science Institute, Hasselt University, Hasselt, Belgium
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3
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Murray JM, Murray DD, Schvoerer E, Akand EH. SARS-CoV-2 Delta and Omicron community transmission networks as added value to contact tracing. J Infect 2024; 88:173-179. [PMID: 38242366 DOI: 10.1016/j.jinf.2024.01.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Accepted: 01/14/2024] [Indexed: 01/21/2024]
Abstract
OBJECTIVES Calculations of SARS-CoV-2 transmission networks at a population level have been limited. Networks that estimate infections between individuals and whether this results in a mutation, can be a way to evaluate fitness of a mutational clone by how much it expands in number as well as determining the likelihood a transmission results in a new variant. METHODS Australian Delta and Omicron SARS-CoV-2 sequences were downloaded from GISAID. Transmission networks of infection between individuals were estimated using a novel mathematical method. RESULTS Many of the sequences were identical, with clone sizes following power law distributions driven by negative binomial probability distributions for both the number of infections per individual and the number of mutations per transmission (median 0.74 nucleotide changes for Delta and 0.71 for Omicron). Using these distributions, an agent-based model was able to replicate the observed clonal network structure, providing a basis for more detailed COVID-19 modelling. Possible recombination events, tracked by insertion/deletion (indel) patterns, were identified for each variant in these outbreaks. CONCLUSIONS This modelling approach reveals key transmission characteristics of SARS-CoV-2 and may complement traditional contact tracing. This methodology can also be applied to other diseases as genetic sequencing of viruses becomes more commonplace.
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Affiliation(s)
- John M Murray
- School of Mathematics and Statistics, UNSW Sydney, NSW 2052, Australia.
| | - Daniel D Murray
- Centre of Excellence for Health, Immunity and Infections (CHIP), Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Evelyne Schvoerer
- Laboratory of Virology, University Hospital of Nancy Brabois, F-54500 Vandoeuvre-les-Nancy, France; Lorraine University, Laboratory of Physical Chemistry and Microbiology for Materials and the Environment, LCPME UMR 7564, CNRS, 405 Rue de Vandoeuvre, F-54600 Villers-lès-Nancy, France
| | - Elma H Akand
- School of Mathematics and Statistics, UNSW Sydney, NSW 2052, Australia
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Geenen C, Thibaut J, Laenen L, Raymenants J, Cuypers L, Maes P, Dellicour S, André E. Unravelling the effect of New Year's Eve celebrations on SARS-CoV-2 transmission. Sci Rep 2023; 13:22195. [PMID: 38097713 PMCID: PMC10721646 DOI: 10.1038/s41598-023-49678-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2022] [Accepted: 12/11/2023] [Indexed: 12/17/2023] Open
Abstract
Public holidays have been associated with SARS-CoV-2 incidence surges, although a firm link remains to be established. This association is sometimes attributed to events where transmissions occur at a disproportionately high rate, known as superspreading events. Here, we describe a sudden surge in new cases with the Omicron BA.1 strain amongst higher education students in Belgium. Contact tracers classed most of these cases as likely or possibly infected on New Year's Eve, indicating a direct trigger by New Year celebrations. Using a combination of contact tracing and phylogenetic data, we show the limited role of superspreading events in this surge. Finally, the numerous simultaneous transmissions allowed a unique opportunity to determine the distribution of incubation periods of the Omicron strain. Overall, our results indicate that, even under social restrictions, a surge in transmissibility of SARS-CoV-2 can occur when holiday celebrations result in small social gatherings attended simultaneously and communitywide.
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Affiliation(s)
- Caspar Geenen
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium.
| | - Jonathan Thibaut
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Lies Laenen
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
- Department of Laboratory Medicine, National Reference Centre for Respiratory Pathogens, University Hospitals Leuven, Leuven, Belgium
| | - Joren Raymenants
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
| | - Lize Cuypers
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
- Department of Laboratory Medicine, National Reference Centre for Respiratory Pathogens, University Hospitals Leuven, Leuven, Belgium
| | - Piet Maes
- Rega Institute, Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium
| | - Simon Dellicour
- Rega Institute, Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical and Epidemiological Virology, KU Leuven, Leuven, Belgium
- Spatial Epidemiology Lab, Université Libre de Bruxelles, Brussels, Belgium
| | - Emmanuel André
- Department of Microbiology, Immunology and Transplantation, Laboratory of Clinical Microbiology, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
- Department of Laboratory Medicine, National Reference Centre for Respiratory Pathogens, University Hospitals Leuven, Leuven, Belgium
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5
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Pasquale DK, Welsh W, Olson A, Yacoub M, Moody J, Barajas Gomez BA, Bentley-Edwards KL, McCall J, Solis-Guzman ML, Dunn JP, Woods CW, Petzold EA, Bowie AC, Singh K, Huang ES. Scalable Strategies to Increase Efficiency and Augment Public Health Activities During Epidemic Peaks. JOURNAL OF PUBLIC HEALTH MANAGEMENT AND PRACTICE 2023; 29:863-873. [PMID: 37379511 PMCID: PMC10549909 DOI: 10.1097/phh.0000000000001780] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/30/2023]
Abstract
OBJECTIVE Scalable strategies to reduce the time burden and increase contact tracing efficiency are crucial during early waves and peaks of infectious transmission. DESIGN We enrolled a cohort of SARS-CoV-2-positive seed cases into a peer recruitment study testing social network methodology and a novel electronic platform to increase contact tracing efficiency. SETTING Index cases were recruited from an academic medical center and requested to recruit their local social contacts for enrollment and SARS-CoV-2 testing. PARTICIPANTS A total of 509 adult participants enrolled over 19 months (384 seed cases and 125 social peers). INTERVENTION Participants completed a survey and were then eligible to recruit their social contacts with unique "coupons" for enrollment. Peer participants were eligible for SARS-CoV-2 and respiratory pathogen screening. MAIN OUTCOME MEASURES The main outcome measures were the percentage of tests administered through the study that identified new SARS-CoV-2 cases, the feasibility of deploying the platform and the peer recruitment strategy, the perceived acceptability of the platform and the peer recruitment strategy, and the scalability of both during pandemic peaks. RESULTS After development and deployment, few human resources were needed to maintain the platform and enroll participants, regardless of peaks. Platform acceptability was high. Percent positivity tracked with other testing programs in the area. CONCLUSIONS An electronic platform may be a suitable tool to augment public health contact tracing activities by allowing participants to select an online platform for contact tracing rather than sitting for an interview.
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Affiliation(s)
- Dana K. Pasquale
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Whitney Welsh
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Andrew Olson
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Mark Yacoub
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - James Moody
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Brisa A. Barajas Gomez
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Keisha L. Bentley-Edwards
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Jonathan McCall
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Maria Luisa Solis-Guzman
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Jessilyn P. Dunn
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Christopher W. Woods
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Elizabeth A. Petzold
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Aleah C. Bowie
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Karnika Singh
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
| | - Erich S. Huang
- Department of Population Health Sciences (Dr Pasquale), Department of Sociology (Drs Pasquale and Moody), Social Science Research Institute (Dr Welsh), Duke AI Health, School of Medicine (Messrs Olson and McCall), Duke Population Research Institute (Mr Yacoub), Duke Network Analysis Center (Dr Moody), Duke Office of Clinical Research, School of Medicine (Ms Barajas Gomez), Samuel DuBois Cook Center on Social Equity (Dr Bentley-Edwards), Department of Biomedical Engineering, Pratt School of Engineering (Dr Dunn and Ms Singh), Department of Biostatistics & Bioinformatics (Drs Dunn and Huang), Department of Medicine, School of Medicine (Dr Woods), Duke Global Health Institute (Dr Woods), Center for Infectious Disease Diagnostics & Innovation (Drs Petzold and Bowie), and Department of Surgery (Dr Huang), Duke University, Durham, North Carolina; LUMA Consulting, Durham, North Carolina (Ms Solis-Guzman); and Verily Life Sciences, South San Francisco, California (Dr Huang)
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6
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Kremer C, Willem L, Boone J, Arrazola de Oñate W, Hammami N, Faes C, Hens N. Key performance indicators of COVID-19 contact tracing in Belgium from September 2020 to December 2021. PLoS One 2023; 18:e0292346. [PMID: 37862313 PMCID: PMC10588862 DOI: 10.1371/journal.pone.0292346] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Accepted: 09/18/2023] [Indexed: 10/22/2023] Open
Abstract
The goal of tracing, testing, and quarantining contacts of infected individuals is to contain the spread of infectious diseases, a strategy widely used during the COVID-19 pandemic. However, limited research exists on the effectiveness of contact tracing, especially with regard to key performance indicators (KPIs), such as the proportion of cases arising from previously identified contacts. In our study, we analyzed contact tracing data from Belgium collected between September 2020 and December 2021 to assess the impact of contact tracing on SARS-CoV-2 transmission and understand its characteristics. Among confirmed cases involved in contact tracing in the Flemish and Brussels-Capital regions, 19.1% were previously identified as close contacts and were aware of prior exposure. These cases, referred to as 'known' to contact tracing operators, reported on average fewer close contacts compared to newly identified individuals (0.80 versus 1.05), resulting in fewer secondary cases (0.23 versus 0.28). Additionally, we calculated the secondary attack rate, representing infections per contact, which was on average lower for the 'known' cases (0.22 versus 0.25) between December 2020 and August 2021. These findings indicate the effectiveness of contact tracing in Belgium in reducing SARS-CoV-2 transmission. Although we were unable to quantify the exact number of prevented cases, our findings emphasize the importance of contact tracing as a public health measure. In addition, contact tracing data provide indications of potential shifts in transmission patterns among different age groups associated with emerging variants of concern and increasing vaccination rates.
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Affiliation(s)
- Cécile Kremer
- Interuniversity Institute for Biostatistics and statistical Bioinformatics, Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Lander Willem
- Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
- Family Medicine and Population Health, University of Antwerp, Antwerp, Belgium
| | - Jorden Boone
- KPMG Advisory, Public Sector Practice, Zaventem, Belgium
| | - Wouter Arrazola de Oñate
- Belgian Lung and Tuberculosis Association, Brussels, Belgium
- Flemish Association for Respiratory Health and Tuberculosis, Leuven, Belgium
| | - Naïma Hammami
- Department of Infectious Disease Prevention and Control, Department of Care, Flemish Region, Brussels, Belgium
| | - Christel Faes
- Interuniversity Institute for Biostatistics and statistical Bioinformatics, Data Science Institute, Hasselt University, Hasselt, Belgium
| | - Niel Hens
- Interuniversity Institute for Biostatistics and statistical Bioinformatics, Data Science Institute, Hasselt University, Hasselt, Belgium
- Centre for Health Economics Research and Modelling Infectious Diseases, Vaccine and Infectious Disease Institute, University of Antwerp, Antwerp, Belgium
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7
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Xu X, Wu Y, Kummer AG, Zhao Y, Hu Z, Wang Y, Liu H, Ajelli M, Yu H. Assessing changes in incubation period, serial interval, and generation time of SARS-CoV-2 variants of concern: a systematic review and meta-analysis. BMC Med 2023; 21:374. [PMID: 37775772 PMCID: PMC10541713 DOI: 10.1186/s12916-023-03070-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 09/05/2023] [Indexed: 10/01/2023] Open
Abstract
BACKGROUND After the first COVID-19 wave caused by the ancestral lineage, the pandemic has been fueled from the continuous emergence of new SARS-CoV-2 variants. Understanding key time-to-event periods for each emerging variant of concern is critical as it can provide insights into the future trajectory of the virus and help inform outbreak preparedness and response planning. Here, we aim to examine how the incubation period, serial interval, and generation time have changed from the ancestral SARS-CoV-2 lineage to different variants of concern. METHODS We conducted a systematic review and meta-analysis that synthesized the estimates of incubation period, serial interval, and generation time (both realized and intrinsic) for the ancestral lineage, Alpha, Beta, and Omicron variants of SARS-CoV-2. RESULTS Our study included 280 records obtained from 147 household studies, contact tracing studies, or studies where epidemiological links were known. With each emerging variant, we found a progressive shortening of each of the analyzed key time-to-event periods, although we did not find statistically significant differences between the Omicron subvariants. We found that Omicron BA.1 had the shortest pooled estimates for the incubation period (3.49 days, 95% CI: 3.13-4.86 days), Omicron BA.5 for the serial interval (2.37 days, 95% CI: 1.71-3.04 days), and Omicron BA.1 for the realized generation time (2.99 days, 95% CI: 2.48-3.49 days). Only one estimate for the intrinsic generation time was available for Omicron subvariants: 6.84 days (95% CrI: 5.72-8.60 days) for Omicron BA.1. The ancestral lineage had the highest pooled estimates for each investigated key time-to-event period. We also observed shorter pooled estimates for the serial interval compared to the incubation period across the virus lineages. When pooling the estimates across different virus lineages, we found considerable heterogeneities (I2 > 80%; I2 refers to the percentage of total variation across studies that is due to heterogeneity rather than chance), possibly resulting from heterogeneities between the different study populations (e.g., deployed interventions, social behavior, demographic characteristics). CONCLUSIONS Our study supports the importance of conducting contact tracing and epidemiological investigations to monitor changes in SARS-CoV-2 transmission patterns. Our findings highlight a progressive shortening of the incubation period, serial interval, and generation time, which can lead to epidemics that spread faster, with larger peak incidence, and harder to control. We also consistently found a shorter serial interval than incubation period, suggesting that a key feature of SARS-CoV-2 is the potential for pre-symptomatic transmission. These observations are instrumental to plan for future COVID-19 waves.
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Affiliation(s)
- Xiangyanyu Xu
- School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China
| | - Yanpeng Wu
- Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai, China
| | - Allisandra G Kummer
- Laboratory of Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA
| | - Yuchen Zhao
- Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai, China
| | - Zexin Hu
- Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai, China
| | - Yan Wang
- School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China
| | - Hengcong Liu
- School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China
| | - Marco Ajelli
- Laboratory of Computational Epidemiology and Public Health, Department of Epidemiology and Biostatistics, Indiana University School of Public Health, Bloomington, IN, USA.
| | - Hongjie Yu
- School of Public Health, Fudan University, Key Laboratory of Public Health Safety, Ministry of Education, Shanghai, China.
- Shanghai Institute of Infectious Disease and Biosecurity, Fudan University, Shanghai, China.
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8
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Geismar C, Nguyen V, Fragaszy E, Shrotri M, Navaratnam AMD, Beale S, Byrne TE, Fong WLE, Yavlinsky A, Kovar J, Hoskins S, Braithwaite I, Aldridge RW, Hayward AC, White PJ, Jombart T, Cori A. Bayesian reconstruction of SARS-CoV-2 transmissions highlights substantial proportion of negative serial intervals. Epidemics 2023; 44:100713. [PMID: 37579586 DOI: 10.1016/j.epidem.2023.100713] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 07/25/2023] [Accepted: 07/31/2023] [Indexed: 08/16/2023] Open
Abstract
BACKGROUND The serial interval is a key epidemiological measure that quantifies the time between the onset of symptoms in an infector-infectee pair. It indicates how quickly new generations of cases appear, thus informing on the speed of an epidemic. Estimating the serial interval requires to identify pairs of infectors and infectees. Yet, most studies fail to assess the direction of transmission between cases and assume that the order of infections - and thus transmissions - strictly follows the order of symptom onsets, thereby imposing serial intervals to be positive. Because of the long and highly variable incubation period of SARS-CoV-2, this may not always be true (i.e an infectee may show symptoms before their infector) and negative serial intervals may occur. This study aims to estimate the serial interval of different SARS-CoV-2 variants whilst accounting for negative serial intervals. METHODS This analysis included 5 842 symptomatic individuals with confirmed SARS-CoV-2 infection amongst 2 579 households from September 2020 to August 2022 across England & Wales. We used a Bayesian framework to infer who infected whom by exploring all transmission trees compatible with the observed dates of symptoms, based on a wide range of incubation period and generation time distributions compatible with estimates reported in the literature. Serial intervals were derived from the reconstructed transmission pairs, stratified by variants. RESULTS We estimated that 22% (95% credible interval (CrI) 8-32%) of serial interval values are negative across all VOC. The mean serial interval was shortest for Omicron BA5 (2.02 days, 1.26-2.84) and longest for Alpha (3.37 days, 2.52-4.04). CONCLUSIONS This study highlights the large proportion of negative serial intervals across SARS-CoV-2 variants. Because the serial interval is widely used to estimate transmissibility and forecast cases, these results may have critical implications for epidemic control.
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Affiliation(s)
- Cyril Geismar
- MRC Centre for Global Infectious Disease Analysis and NIHR Health Protection Research Unit in Modelling and Health Economics, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK; Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK.
| | - Vincent Nguyen
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Ellen Fragaszy
- Institute of Epidemiology and Health Care, University College London, London, UK; Department of Infectious Disease Epidemiology, London School of Hygiene & Tropical Medicine, London, UK
| | - Madhumita Shrotri
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Annalan M D Navaratnam
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Sarah Beale
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK; Institute of Epidemiology and Health Care, University College London, London, UK
| | - Thomas E Byrne
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Wing Lam Erica Fong
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Alexei Yavlinsky
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Jana Kovar
- Institute of Epidemiology and Health Care, University College London, London, UK
| | - Susan Hoskins
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Isobel Braithwaite
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Robert W Aldridge
- Centre for Public Health Data Science, Institute of Health Informatics, University College London, London, UK
| | - Andrew C Hayward
- Institute of Epidemiology and Health Care, University College London, London, UK
| | - Peter J White
- MRC Centre for Global Infectious Disease Analysis and NIHR Health Protection Research Unit in Modelling and Health Economics, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Thibaut Jombart
- MRC Centre for Global Infectious Disease Analysis and NIHR Health Protection Research Unit in Modelling and Health Economics, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
| | - Anne Cori
- MRC Centre for Global Infectious Disease Analysis and NIHR Health Protection Research Unit in Modelling and Health Economics, Department of Infectious Disease Epidemiology, School of Public Health, Imperial College London, London, UK
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9
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Zhang S, Liu L, Meng Q, Zhang Y, Yang H, Xu G. Spatiotemporal Patterns of the Omicron Wave of COVID-19 in the United States. Trop Med Infect Dis 2023; 8:349. [PMID: 37505645 PMCID: PMC10385263 DOI: 10.3390/tropicalmed8070349] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2023] [Revised: 06/20/2023] [Accepted: 06/26/2023] [Indexed: 07/29/2023] Open
Abstract
COVID-19 has undergone multiple mutations, with the Omicron variant proving to be highly contagious and rapidly spreading across many countries. The United States was severely hit by the Omicron variant. However, it was still unclear how Omicron transferred across the United States. Here, we collected daily COVID-19 cases and deaths in each county from 1 December 2021 to 28 February 2022 as the Omicron wave. We adopted space-time scan statistics, the Hoover index, and trajectories of the epicenter to quantify spatiotemporal patterns of the Omicron wave of COVID-19. The results showed that the highest and earliest cluster was located in the Northeast. The Hoover index for both cases and deaths exhibited phases of rapid decline, slow decline, and relative stability, indicating a rapid spread of the Omicron wave across the country. The Hoover index for deaths was consistently higher than that for cases. The epicenter of cases and deaths shifted from the west to the east, then southwest. Nevertheless, cases were more widespread than deaths, with a lag in mortality data. This study uncovers the spatiotemporal patterns of Omicron transmission in the United States, and its underlying mechanisms deserve further exploration.
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Affiliation(s)
- Siyuan Zhang
- School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China
| | - Liran Liu
- School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China
| | - Qingxiang Meng
- School of Remote Sensing and Information Engineering, Wuhan University, Wuhan 430079, China
| | - Yixuan Zhang
- School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China
| | - He Yang
- Transportation Development Center of Henan Province, Zhengzhou 450016, China
| | - Gang Xu
- School of Resource and Environmental Sciences, Wuhan University, Wuhan 430079, China
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10
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Madewell ZJ, Yang Y, Longini IM, Halloran ME, Vespignani A, Dean NE. Rapid review and meta-analysis of serial intervals for SARS-CoV-2 Delta and Omicron variants. BMC Infect Dis 2023; 23:429. [PMID: 37365505 DOI: 10.1186/s12879-023-08407-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Accepted: 06/20/2023] [Indexed: 06/28/2023] Open
Abstract
BACKGROUND The serial interval is the period of time between symptom onset in the primary case and symptom onset in the secondary case. Understanding the serial interval is important for determining transmission dynamics of infectious diseases like COVID-19, including the reproduction number and secondary attack rates, which could influence control measures. Early meta-analyses of COVID-19 reported serial intervals of 5.2 days (95% CI: 4.9-5.5) for the original wild-type variant and 5.2 days (95% CI: 4.87-5.47) for Alpha variant. The serial interval has been shown to decrease over the course of an epidemic for other respiratory diseases, which may be due to accumulating viral mutations and implementation of more effective nonpharmaceutical interventions. We therefore aggregated the literature to estimate serial intervals for Delta and Omicron variants. METHODS This study followed Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. A systematic literature search was conducted of PubMed, Scopus, Cochrane Library, ScienceDirect, and preprint server medRxiv for articles published from April 4, 2021, through May 23, 2023. Search terms were: ("serial interval" or "generation time"), ("Omicron" or "Delta"), and ("SARS-CoV-2" or "COVID-19"). Meta-analyses were done for Delta and Omicron variants using a restricted maximum-likelihood estimator model with a random effect for each study. Pooled average estimates and 95% confidence intervals (95% CI) are reported. RESULTS There were 46,648 primary/secondary case pairs included for the meta-analysis of Delta and 18,324 for Omicron. Mean serial interval for included studies ranged from 2.3-5.8 days for Delta and 2.1-4.8 days for Omicron. The pooled mean serial interval for Delta was 3.9 days (95% CI: 3.4-4.3) (20 studies) and Omicron was 3.2 days (95% CI: 2.9-3.5) (20 studies). Mean estimated serial interval for BA.1 was 3.3 days (95% CI: 2.8-3.7) (11 studies), BA.2 was 2.9 days (95% CI: 2.7-3.1) (six studies), and BA.5 was 2.3 days (95% CI: 1.6-3.1) (three studies). CONCLUSIONS Serial interval estimates for Delta and Omicron were shorter than ancestral SARS-CoV-2 variants. More recent Omicron subvariants had even shorter serial intervals suggesting serial intervals may be shortening over time. This suggests more rapid transmission from one generation of cases to the next, consistent with the observed faster growth dynamic of these variants compared to their ancestors. Additional changes to the serial interval may occur as SARS-CoV-2 continues to circulate and evolve. Changes to population immunity (due to infection and/or vaccination) may further modify it.
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Affiliation(s)
- Zachary J Madewell
- Department of Biostatistics, University of Florida, Gainesville, FL, USA.
| | - Yang Yang
- Department of Statistics, University of Georgia, Athens, GA, USA
| | - Ira M Longini
- Department of Biostatistics, University of Florida, Gainesville, FL, USA
| | - M Elizabeth Halloran
- Department of Biostatistics, University of Washington, Seattle, WA, USA
- Fred Hutchinson Cancer Center, Seattle, WA, USA
| | - Alessandro Vespignani
- Laboratory for the Modeling of Biological and Socio-Technical Systems, Northeastern University, Boston, MA, USA
| | - Natalie E Dean
- Department of Biostatistics and Bioinformatics, Emory University, Atlanta, GA, USA
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11
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Yuan B, Liu R, Tang S. Assessing the transmissibility of epidemics involving epidemic zoning. BMC Infect Dis 2023; 23:242. [PMID: 37072732 PMCID: PMC10111305 DOI: 10.1186/s12879-023-08205-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Accepted: 03/28/2023] [Indexed: 04/20/2023] Open
Abstract
BACKGROUND Epidemic zoning is an important option in a series of measures for the prevention and control of infectious diseases. We aim to accurately assess the disease transmission process by considering the epidemic zoning, and we take two epidemics with distinct outbreak sizes as an example, i.e., the Xi'an epidemic in late 2021 and the Shanghai epidemic in early 2022. METHODS For the two epidemics, the total cases were clearly distinguished by their reporting zone and the Bernoulli counting process was used to describe whether one infected case in society would be reported in control zones or not. Assuming the imperfect or perfect isolation policy in control zones, the transmission processes are respectively simulated by the adjusted renewal equation with case importation, which can be derived on the basis of the Bellman-Harris branching theory. The likelihood function containing unknown parameters is then constructed by assuming the daily number of new cases reported in control zones follows a Poisson distribution. All the unknown parameters were obtained by the maximum likelihood estimation. RESULTS For both epidemics, the internal infections characterized by subcritical transmission within the control zones were verified, and the median control reproduction numbers were estimated as 0.403 (95% confidence interval (CI): 0.352, 0.459) in Xi'an epidemic and 0.727 (95% CI: 0.724, 0.730) in Shanghai epidemic, respectively. In addition, although the detection rate of social cases quickly increased to 100% during the decline period of daily new cases until the end of the epidemic, the detection rate in Xi'an was significantly higher than that in Shanghai in the previous period. CONCLUSIONS The comparative analysis of the two epidemics with different consequences highlights the role of the higher detection rate of social cases since the beginning of the epidemic and the reduced transmission risk in control zones throughout the outbreak. Strengthening the detection of social infection and strictly implementing the isolation policy are of great significance to avoid a larger-scale epidemic.
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Affiliation(s)
- Baoyin Yuan
- School of Mathematics, South China University of Technology, Guangzhou, 510640, China
| | - Rui Liu
- School of Mathematics, South China University of Technology, Guangzhou, 510640, China.
- Pazhou Lab, Guangzhou, 510330, China.
| | - Sanyi Tang
- School of Mathematics and Statistics, Shaanxi Normal University, Xi'an 710119, China.
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12
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Wang K, Luan Z, Guo Z, Lei H, Zeng T, Yu L, Li H, Tian M, Ran J, Zhao S. Superspreading potentials of SARS-CoV-2 Delta variants across different contact settings in Eastern China: A retrospective observational study. J Infect Public Health 2023; 16:689-696. [PMID: 36934643 PMCID: PMC9985516 DOI: 10.1016/j.jiph.2023.02.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 02/23/2023] [Accepted: 02/27/2023] [Indexed: 03/07/2023] Open
Abstract
OBJECTIVES As the genetic variants of SARS-CoV-2 continuously pose threats to global health, evaluating superspreading potentials of emerging genetic variants is of importance for region-wide control of COVID-19 outbreaks. METHODS By using detailed epidemiological contact tracing data of test-positive COVID-19 cases collected between July and August 2021 in Nanjing and Yangzhou, China, we assessed the superspreading potential of outbreaks seeded by SARS-CoV-2 Delta variants. The transmission chains and case-clusters were constructed according to the individual-based surveillance data. We modelled the disease transmission as a classic branching process with transmission heterogeneity governed by negative binomial models. Subgroup analysis was conducted by different contact settings and age groups. RESULTS We reported a considerable heterogeneity in the contact patterns and transmissibility of Delta variants in eastern China. We estimated an expected 14% (95% CI: 11-16%) of the most infectious cases generated 80% of the total transmission. CONCLUSIONS Delta variants demonstrated a significant potential of superspreading under strict control measures and active COVID-19 detecting efforts. Enhancing the surveillance on disease transmissibility especially in high-risk settings, along with rapid contact tracing and case isolations would be one of the key factors to mitigate the epidemic caused by the emerging genetic variants of SARS-CoV-2.
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Affiliation(s)
- Kai Wang
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830017, China.
| | - Zemin Luan
- School of Public Health, Xinjiang Medical University, Urumqi 830017, China
| | - Zihao Guo
- JC School of Public Health and Primary Care, Chinese University of Hong Kong, 999077, Hong Kong SAR, China
| | - Hao Lei
- School of Public Health, Zhejiang University, Hangzhou 310058, China
| | - Ting Zeng
- School of Public Health, Xinjiang Medical University, Urumqi 830017, China
| | - Lin Yu
- Faculty of Arts and Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Hujiaojiao Li
- Faculty of Arts and Sciences, University of Toronto, Toronto, Ontario, Canada
| | - Maozai Tian
- State Key Laboratory of Pathogenesis, Prevention and Treatment of High Incidence Diseases in Central Asia, Department of Medical Engineering and Technology, Xinjiang Medical University, Urumqi 830017, China
| | - Jinjun Ran
- School of Public Health, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Shi Zhao
- Department of Epidemiology and Biostatistics, School of Public Health, Capital Medical University, Beijing 100069, China; Centre for Health Systems and Policy Research, Chinese University of Hong Kong, 999077, Hong Kong SAR, China.
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13
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Guo Z, Zhao S, Yam CHK, Li C, Jiang X, Chow TY, Chong KC, Yeoh EK. Estimating the serial intervals of SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 variants in Hong Kong. Influenza Other Respir Viruses 2023; 17:e13105. [PMID: 36824395 PMCID: PMC9942273 DOI: 10.1111/irv.13105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 01/12/2023] [Accepted: 01/15/2023] [Indexed: 02/10/2023] Open
Abstract
Empirical evidence on the epidemiological characteristics of the emerged SARS-CoV-2 variants could shed light on the transmission potential of the virus and strategic outbreak control planning. In this study, by using contact tracing data collected during an Omicron-predominant epidemic phase in Hong Kong, we estimated the mean serial interval of SARS-CoV-2 Omicron BA.4, BA.5, and BA.2.12.1 variants at 2.8 days (95% credible interval [CrI]: 1.5, 6.7), 2.7 days (95% CrI: 2.1, 3.6), and 4.4 days (95% CrI: 2.6, 7.5), respectively, with adjustment for right truncation and sampling bias. The short serial interval for the current circulating variant indicated that outbreak mitigations through contact tracing and case isolation would be quite challenging.
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Affiliation(s)
- Zihao Guo
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Shi Zhao
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina,Centre for Health Systems and Policy Research, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Carrie Ho Kwan Yam
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina,Centre for Health Systems and Policy Research, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Conglu Li
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Xiaoting Jiang
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Tsz Yu Chow
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina,Centre for Health Systems and Policy Research, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Ka Chun Chong
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina,Centre for Health Systems and Policy Research, Faculty of MedicineChinese University of Hong KongHong KongChina
| | - Eng Kiong Yeoh
- JC School of Public Health and Primary Care, Faculty of MedicineChinese University of Hong KongHong KongChina,Centre for Health Systems and Policy Research, Faculty of MedicineChinese University of Hong KongHong KongChina
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14
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Wei Z, Ma W, Wang Z, Li J, Fu X, Chang H, Qiu Y, Tian H, Zhu Y, Xia A, Wu Q, Liu G, Zhai X, Zhang X, Wang Y, Zeng M. Household transmission of SARS-CoV-2 during the Omicron wave in Shanghai, China: A case-ascertained study. Influenza Other Respir Viruses 2023; 17:e13097. [PMID: 36843225 PMCID: PMC9946695 DOI: 10.1111/irv.13097] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Revised: 01/03/2023] [Accepted: 01/04/2023] [Indexed: 02/07/2023] Open
Abstract
OBJECTIVES We used a case-ascertained study to determine the features of household transmission of SARS-CoV-2 Omicron variant in Shanghai, China. METHODS In April 2022, we carried out a household transmission study from 309 households of 335 SARS-CoV-2 pediatric cases referred to a designated tertiary Children's Hospital. The detailed information can be collected from the 297 households for estimating the transmission parameters. The 236 households were qualified for estimating the secondary infection attack rates (SARI ) and secondary clinical attack rates (SARC ) among adult household contacts, characterizing the transmission heterogeneities in infectivity and susceptibility, and assessing the vaccine effectiveness. RESULTS We estimated the mean incubation period and serial interval of Omicron variant to be 4.6 ± 2.1 and 3.9 ± 3.7 days, respectively, with 57.2% of the transmission events occurring at the presymptomatic phase. The overall SARI and SARC among adult household contacts were 77.11% (95% confidence interval [CI]: 73.58%-80.63%) and 67.03% (63.09%-70.98%). We found higher household susceptibility in females. Infectivity was not significantly different between children and adults and symptomatic and asymptomatic cases. Two-dose and booster-dose of inactivated COVID-19 vaccination were 14.8% (5.8%-22.9%) and 18.9% (9.0%-27.7%) effective against Omicron infection and 21.5% (10.4%-31.2%) and 24.3% (12.3%-34.7%) effective against the symptomatic disease. CONCLUSIONS We found high household transmission during the Omicron wave in Shanghai due to presymptomatic and asymptomatic transmission despite implementation of strict interventions, indicating the importance of early detection and timely isolation of SARS-CoV-2 infections. Marginal effectiveness of inactivated vaccines against Omicron infection poses a great challenge for outbreak containment.
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Affiliation(s)
- Zhongqiu Wei
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Wenjie Ma
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Zhonglin Wang
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Jingjing Li
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Xiaomin Fu
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Hailing Chang
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Yue Qiu
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - He Tian
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Yanfeng Zhu
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Aimei Xia
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina
| | - Qianhui Wu
- School of Public HealthFudan University, Key Laboratory of Public Health Safety, Ministry of EducationShanghaiChina
| | - Gongbao Liu
- Department of MedicineChildren's Hospital of Fudan UniversityShanghaiChina
| | - Xiaowen Zhai
- Department of Hematology and OncologyChildren's Hospital of Fudan UniversityShanghaiChina
| | - Xiaobo Zhang
- Department of Respiratory MedicineChildren's Hospital of Fudan UniversityShanghaiChina
| | - Yan Wang
- School of Public HealthFudan University, Key Laboratory of Public Health Safety, Ministry of EducationShanghaiChina
| | - Mei Zeng
- Department of Infectious DiseaseChildren's Hospital of Fudan UniversityShanghaiChina,Shanghai Institute of Infectious Disease and BiosecurityFudan UniversityShanghaiChina
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15
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Gressani O, Wallinga J, Althaus CL, Hens N, Faes C. EpiLPS: A fast and flexible Bayesian tool for estimation of the time-varying reproduction number. PLoS Comput Biol 2022; 18:e1010618. [PMID: 36215319 PMCID: PMC9584461 DOI: 10.1371/journal.pcbi.1010618] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 10/20/2022] [Accepted: 09/30/2022] [Indexed: 11/17/2022] Open
Abstract
In infectious disease epidemiology, the instantaneous reproduction number [Formula: see text] is a time-varying parameter defined as the average number of secondary infections generated by an infected individual at time t. It is therefore a crucial epidemiological statistic that assists public health decision makers in the management of an epidemic. We present a new Bayesian tool (EpiLPS) for robust estimation of the time-varying reproduction number. The proposed methodology smooths the epidemic curve and allows to obtain (approximate) point estimates and credible intervals of [Formula: see text] by employing the renewal equation, using Bayesian P-splines coupled with Laplace approximations of the conditional posterior of the spline vector. Two alternative approaches for inference are presented: (1) an approach based on a maximum a posteriori argument for the model hyperparameters, delivering estimates of [Formula: see text] in only a few seconds; and (2) an approach based on a Markov chain Monte Carlo (MCMC) scheme with underlying Langevin dynamics for efficient sampling of the posterior target distribution. Case counts per unit of time are assumed to follow a negative binomial distribution to account for potential overdispersion in the data that would not be captured by a classic Poisson model. Furthermore, after smoothing the epidemic curve, a "plug-in'' estimate of the reproduction number can be obtained from the renewal equation yielding a closed form expression of [Formula: see text] as a function of the spline parameters. The approach is extremely fast and free of arbitrary smoothing assumptions. EpiLPS is applied on data of SARS-CoV-1 in Hong-Kong (2003), influenza A H1N1 (2009) in the USA and on the SARS-CoV-2 pandemic (2020-2021) for Belgium, Portugal, Denmark and France.
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Affiliation(s)
- Oswaldo Gressani
- Interuniversity Institute for Biostatistics and statistical Bioinformatics (I-BioStat), Data Science Institute, Hasselt University, Hasselt, Belgium,* E-mail:
| | - Jacco Wallinga
- Centre for Infectious Disease Control, National Institute for Public Health and the Environment, Bilthoven, The Netherlands,Department of Biomedical Data Sciences, Leiden University Medical Centre, Leiden, The Netherlands
| | - Christian L. Althaus
- Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
| | - Niel Hens
- Interuniversity Institute for Biostatistics and statistical Bioinformatics (I-BioStat), Data Science Institute, Hasselt University, Hasselt, Belgium,Centre for Health Economics Research and Modelling Infectious Diseases, Vaxinfectio, University of Antwerp, Antwerp, Belgium
| | - Christel Faes
- Interuniversity Institute for Biostatistics and statistical Bioinformatics (I-BioStat), Data Science Institute, Hasselt University, Hasselt, Belgium
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Chen SLS, Jen GHH, Hsu CY, Yen AMF, Lai CC, Yeh YP, Chen THH. A new approach to modeling pre-symptomatic incidence and transmission time of imported COVID-19 cases evolving with SARS-CoV-2 variants. STOCHASTIC ENVIRONMENTAL RESEARCH AND RISK ASSESSMENT : RESEARCH JOURNAL 2022; 37:441-452. [PMID: 36120386 PMCID: PMC9464357 DOI: 10.1007/s00477-022-02305-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Accepted: 08/24/2022] [Indexed: 06/15/2023]
Abstract
There is paucity of the statistical model that is specified for data on imported COVID-19 cases with the unique global information on infectious properties of SARS-CoV-2 variant different from local outbreak data used for estimating transmission and infectiousness parameters via the established epidemic models. To this end, a new approach with a four-state stochastic model was proposed to formulate these well-established infectious parameters with three new parameters, including the pre-symptomatic incidence rate, the median of pre-symptomatic transmission time (MPTT) to symptomatic state, and the incidence (proportion) of asymptomatic cases using imported COVID-19 data. We fitted the proposed stochastic model to empirical data on imported COVID-19 cases from D614G to Omicron with the corresponding calendar periods according to the classification GISAID information on the evolution of SARS-CoV-2 variant between March 2020 and Jan 2022 in Taiwan. The pre-symptomatic incidence rate was the highest for Omicron followed by Alpha, Delta, and D614G. The MPTT (in days) increased from 3.45 (first period) ~ 4.02 (second period) of D614G until 3.94-4.65 of VOC Alpha but dropped to 3.93-3.49 of Delta and 2 days (only first period) of Omicron. The proportion of asymptomatic cases increased from 29% of D-614G period to 59.2% of Omicron. Modeling data on imported cases across strains of SARS-CoV-2 not only bridges the link between the underlying natural infectious properties elucidated in the previous epidemic models and different disease phenotypes of COVID-19 but also provides precision quarantine and isolation policy for border control in the face of various emerging SRAS-CoV-2 variants globally.
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Affiliation(s)
- Sam Li-Sheng Chen
- School of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
| | - Grace Hsiao-Hsuan Jen
- School of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chen-Yang Hsu
- Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Room 533, No. 17, Hsuchow Road, Taipei, 100 Taiwan
| | - Amy Ming-Fang Yen
- School of Oral Hygiene, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan
| | - Chao-Chih Lai
- Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Room 533, No. 17, Hsuchow Road, Taipei, 100 Taiwan
- Emergency Department of Taipei City Hospital, Ren-Ai Branch, Taipei, Taiwan
| | - Yen-Po Yeh
- Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Room 533, No. 17, Hsuchow Road, Taipei, 100 Taiwan
- Changhua County Public Health Bureau, Changhua, Taiwan
| | - Tony Hsiu-Hsi Chen
- Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Room 533, No. 17, Hsuchow Road, Taipei, 100 Taiwan
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Genomic surveillance of SARS-CoV-2 Omicron variants on a university campus. Nat Commun 2022; 13:5240. [PMID: 36068236 PMCID: PMC9446629 DOI: 10.1038/s41467-022-32786-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Accepted: 08/15/2022] [Indexed: 01/14/2023] Open
Abstract
Novel variants continue to emerge in the SARS-CoV-2 pandemic. University testing programs may provide timely epidemiologic and genomic surveillance data to inform public health responses. We conducted testing from September 2021 to February 2022 in a university population under vaccination and indoor mask mandates. A total of 3,048 of 24,393 individuals tested positive for SARS-CoV-2 by RT-PCR; whole genome sequencing identified 209 Delta and 1,730 Omicron genomes of the 1,939 total sequenced. Compared to Delta, Omicron had a shorter median serial interval between genetically identical, symptomatic infections within households (2 versus 6 days, P = 0.021). Omicron also demonstrated a greater peak reproductive number (2.4 versus 1.8), and a 1.07 (95% confidence interval: 0.58, 1.57; P < 0.0001) higher mean cycle threshold value. Despite near universal vaccination and stringent mitigation measures, Omicron rapidly displaced the Delta variant to become the predominant viral strain and led to a surge in cases in a university population.
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Ahmad A, Fawaz MAM, Aisha A. A comparative overview of SARS-CoV-2 and its variants of concern. LE INFEZIONI IN MEDICINA 2022; 30:328-343. [PMID: 36148164 PMCID: PMC9448317 DOI: 10.53854/liim-3003-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2022] [Accepted: 07/05/2022] [Indexed: 06/16/2023]
Abstract
In December 2019, the severe acute respiratory syndrome 2 (SARS-CoV-2) coronavirus outbreak began in Wuhan, China, and quickly spread to practically every corner of the globe, killing millions of people. SARS-CoV-2 produced numerous variants, five of which have been identified as variants of concern (VOC) by the World Health Organization (WHO) (Alpha, Beta, Gamma, Delta, and Omicron). We conducted a comparative epidemiological analysis of SARS-CoV-2 and its VOC in this paper. We compared the effects of various spike (S) protein mutations in SARS-CoV-2 and its VOC on transmissibility, illness severity, hospitalization risk, fatality rate, immunological evasion, and vaccine efficacy in this review. We also looked into the clinical characteristics of patients infected with SARS-CoV-2 and its VOC.
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Affiliation(s)
- Aqeel Ahmad
- Department of Medical Biochemistry, College of Medicine, Shaqra University, Shaqra, Saudi Arabia
| | - Mohammed Ali Mullah Fawaz
- Department of Microbiology, Aware Medical Education and Research Institute (Aware Group), Shantivanam, Hyderabad, India
| | - Arafeen Aisha
- Department of Pathology, College of Medicine, Majmaah University, Majmaah, Saudi Arabia
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