Browsing by Author "Ruktanonchai, Nick W."

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    Assessing the Effect of Global Travel and Contact Restrictions on Mitigating the COVID-19 Pandemic
    Lai, Shengjie; Ruktanonchai, Nick W.; Carioli, Alessandra; Ruktanonchai, Corrine W.; Floyd, Jessica R.; Prosper, Olivia; Zhang, Chi; Du, Xiangjun; Yang, Weizhong; Tatem, Andrew J. (2021-07)
    Travel restrictions and physical distancing have been implemented across the world to mitigate the coronavirus disease 2019 (COVID-19) pandemic, but studies are needed to understand their effectiveness across regions and time. Based on the population mobility metrics derived from mobile phone geolocation data across 135 countries or territories during the first wave of the pandemic in 2020, we built a metapopulation epidemiological model to measure the effect of travel and contact restrictions on containing COVID-19 outbreaks across regions. We found that if these interventions had not been deployed, the cumulative number of cases could have shown a 97-fold (interquartile range 79-116) increase, as of May 31, 2020. However, their effectiveness depended upon the timing, duration, and intensity of the interventions, with variations in case severity seen across populations, regions, and seasons. Additionally, before effective vaccines are widely available and herd immunity is achieved, our results emphasize that a certain degree of physical distancing at the relaxation of the intervention stage will likely be needed to avoid rapid resurgences and subsequent lockdowns. (C) 2021 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company.
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    Assessing the impact of coordinated COVID-19 exit strategies across Europe
    Ruktanonchai, Nick W.; Floyd, J. R.; Lai, S.; Ruktanonchai, Corrine W.; Sadilek, Adam; Rente-Lourenco, P.; Ben, X.; Carioli, A.; Gwinn, J.; Steele, J. E.; Prosper, Olivia F.; Schneider, A.; Oplinger, A.; Eastham, Paul; Tatem, A. J. (2020-09-18)
    As rates of new coronavirus disease 2019 (COVID-19) cases decline across Europe owing to nonpharmaceutical interventions such as social distancing policies and lockdown measures, countries require guidance on how to ease restrictions while minimizing the risk of resurgent outbreaks. We use mobility and case data to quantify how coordinated exit strategies could delay continental resurgence and limit community transmission of COVID-19. We find that a resurgent continental epidemic could occur as many as 5 weeks earlier when well-connected countries with stringent existing interventions end their interventions prematurely. Further, we find that appropriate coordination can greatly improve the likelihood of eliminating community transmission throughout Europe. In particular, synchronizing intermittent lockdowns across Europe means that half as many lockdown periods would be required to end continent-wide community transmission.
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    Global holiday datasets for understanding seasonal human mobility and population dynamics
    Lai, Shengjie; Sorichetta, Alessandro; Steele, Jessica; Ruktanonchai, Corrine W.; Cunningham, Alexander D.; Rogers, Grant; Koper, Patrycja; Woods, Dorothea; Bondarenko, Maksym; Ruktanonchai, Nick W.; Shi, Weifeng; Tatem, Andrew J. (Nature Portfolio, 2022-01-20)
    Public and school holidays have important impacts on population mobility and dynamics across multiple spatial and temporal scales, subsequently affecting the transmission dynamics of infectious diseases and many socioeconomic activities. However, worldwide data on public and school holidays for understanding their changes across regions and years have not been assembled into a single, open-source and multitemporal dataset. To address this gap, an open access archive of data on public and school holidays in 2010-2019 across the globe at daily, weekly, and monthly timescales was constructed. Airline passenger volumes across 90 countries from 2010 to 2018 were also assembled to illustrate the usage of the holiday data for understanding the changing spatiotemporal patterns of population movements.
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    Impacts of worldwide individual non-pharmaceutical interventions on COVID-19 transmission across waves and space
    Ge, Yong; Zhang, Wen-Bin; Liu, Haiyan; Ruktanonchai, Corrine W.; Hu, Maogui; Wu, Xilin; Song, Yongze; Ruktanonchai, Nick W.; Yan, Wei; Cleary, Eimear; Feng, Luzhao; Li, Zhongjie; Yang, Weizhong; Liu, Mengxiao; Tatem, Andrew J.; Wang, Jin-Feng; Lai, Shengjie (Elsevier, 2022-02-01)
    Governments worldwide have rapidly deployed non-pharmaceutical interventions (NPIs) to mitigate the COVID- 19 pandemic. However, the effect of these individual NPI measures across space and time has yet to be sufficiently assessed, especially with the increase of policy fatigue and the urge for NPI relaxation in the vaccination era. Using the decay ratio in the suppression of COVID-19 infections and multi-source big data, we investigated the changing performance of different NPIs across waves from global and regional levels (in 133 countries) to national and subnational (in the United States of America [USA]) scales before the implementation of mass vaccination. The synergistic effectiveness of all NPIs for reducing COVID-19 infections declined along waves, from 95.4% in the first wave to 56.0% in the third wave recently at the global level and similarly from 83.3% to 58.7% at the USA national level, while it had fluctuating performance across waves on regional and subnational scales. Regardless of geographical scale, gathering restrictions and facial coverings played significant roles in epidemic mitigation before the vaccine rollout. Our findings have important implications for continued tailoring and implementation of NPI strategies, together with vaccination, to mitigate future COVID-19 waves, caused by new variants, and other emerging respiratory infectious diseases.
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    Practical geospatial and sociodemographic predictors of human mobility
    Ruktanonchai, Corrine W.; Lai, Shengjie; Utazi, Chigozie E.; Cunningham, Alex D.; Koper, Patrycja; Rogers, Grant E.; Ruktanonchai, Nick W.; Sadilek, Adam; Woods, Dorothea; Tatem, Andrew J.; Steele, Jessica E.; Sorichetta, Alessandro (2021-07-28)
    Understanding seasonal human mobility at subnational scales has important implications across sciences, from urban planning efforts to disease modelling and control. Assessing how, when, and where populations move over the course of the year, however, requires spatially and temporally resolved datasets spanning large periods of time, which can be rare, contain sensitive information, or may be proprietary. Here, we aim to explore how a set of broadly available covariates can describe typical seasonal subnational mobility in Kenya pre-COVID-19, therefore enabling better modelling of seasonal mobility across low- and middle-income country (LMIC) settings in non-pandemic settings. To do this, we used the Google Aggregated Mobility Research Dataset, containing anonymized mobility flows aggregated over users who have turned on the Location History setting, which is off by default. We combined this with socioeconomic and geospatial covariates from 2018 to 2019 to quantify seasonal changes in domestic and international mobility patterns across years. We undertook a spatiotemporal analysis within a Bayesian framework to identify relevant geospatial and socioeconomic covariates explaining human movement patterns, while accounting for spatial and temporal autocorrelations. Typical pre-pandemic mobility patterns in Kenya mostly consisted of shorter, within-county trips, followed by longer domestic travel between counties and international travel, which is important in establishing how mobility patterns changed post-pandemic. Mobility peaked in August and December, closely corresponding to school holiday seasons, which was found to be an important predictor in our model. We further found that socioeconomic variables including urbanicity, poverty, and female education strongly explained mobility patterns, in addition to geospatial covariates such as accessibility to major population centres and temperature. These findings derived from novel data sources elucidate broad spatiotemporal patterns of how populations move within and beyond Kenya, and can be easily generalized to other LMIC settings before the COVID-19 pandemic. Understanding such pre-pandemic mobility patterns provides a crucial baseline to interpret both how these patterns have changed as a result of the pandemic, as well as whether human mobility patterns have been permanently altered once the pandemic subsides. Our findings outline key correlates of mobility using broadly available covariates, alleviating the data bottlenecks of highly sensitive and proprietary mobile phone datasets, which many researchers do not have access to. These results further provide novel insight on monitoring mobility proxies in the context of disease surveillance and control efforts through LMIC settings.
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    SARS-CoV-2 European resurgence foretold: interplay of introductions and persistence by leveraging genomic and mobility data
    Lemey, Philippe; Ruktanonchai, Nick W.; Hong, Samuel; Colizza, Vittoria; Poletto, Chiara; Van den Broeck, Frederik; Gill, Mandev; Ji, Xiang; Levasseur, Anthony; Sadilek, Adam; Lai, Shengjie; Tatem, Andrew; Baele, Guy; Suchard, Marc; Dellicour, Simon (Springer, 2021-02-10)
    Following the first wave of SARS-CoV-2 infections in spring 2020, Europe experienced a resurgence of the virus starting late summer that was deadlier and more difficult to contain. Relaxed intervention measures and summer travel have been implicated as drivers of the second wave. Here, we build a phylogeographic model to evaluate how newly introduced lineages, as opposed to the rekindling of persistent lineages, contributed to the COVID-19 resurgence in Europe. We inform this model using genomic, mobility and epidemiological data from 10 West European countries and estimate that in many countries more than 50% of the lineages circulating in late summer resulted from new introductions since June 15th. The success in onwards transmission of these lineages is predicted by SARS-CoV-2 incidence during this period. Relatively early introductions from Spain into the United Kingdom contributed to the successful spread of the 20A.EU1/B.1.177 variant. The pervasive spread of variants that have not been associated with an advantage in transmissibility highlights the threat of novel variants of concern that emerged more recently and have been disseminated by holiday travel. Our findings indicate that more effective and coordinated measures are required to contain spread through cross-border travel.
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    Untangling the changing impact of non-pharmaceutical interventions and vaccination on European COVID-19 trajectories
    Ge, Yong; Zhang, Wen-Bin; Wu, Xilin; Ruktanonchai, Corrine W.; Liu, Haiyan; Wang, Jianghao; Song, Yongze; Liu, Mengxiao; Yan, Wei; Yang, Juan; Cleary, Eimear; Qader, Sarchil H.; Atuhaire, Fatumah; Ruktanonchai, Nick W.; Tatem, Andrew J.; Lai, Shengjie (Nature Portfolio, 2022-06)
    Non-pharmaceutical interventions (NPIs) and vaccination are two fundamental approaches for mitigating the coronavirus disease 2019 (COVID-19) pandemic. However, the real-world impact of NPIs versus vaccination, or a combination of both, on COVID-19 remains uncertain. To address this, we built a Bayesian inference model to assess the changing effect of NPIs and vaccination on reducing COVID-19 transmission, based on a large-scale dataset including epidemiological parameters, virus variants, vaccines, and climate factors in Europe from August 2020 to October 2021. We found that (1) the combined effect of NPIs and vaccination resulted in a 53% (95% confidence interval: 42-62%) reduction in reproduction number by October 2021, whereas NPIs and vaccination reduced the transmission by 35% and 38%, respectively; (2) compared with vaccination, the change of NPI effect was less sensitive to emerging variants; (3) the relative effect of NPIs declined 12% from May 2021 due to a lower stringency and the introduction of vaccination strategies. Our results demonstrate that NPIs were complementary to vaccination in an effort to reduce COVID-19 transmission, and the relaxation of NPIs might depend on vaccination rates, control targets, and vaccine effectiveness concerning extant and emerging variants. Non-pharmaceutical interventions (NPIs) and COVID-19 vaccination have been implemented concurrently, making their relative effects difficult to measure. Here, the authors show that effects of NPIs reduced as vaccine coverage increased, but that NPIs could still be important in the context of more transmissible variants.