Infectious disease dynamics and restrictions on social gathering size

Boyer, Christopher B.; Rumpler, Eva; Kissler, Stephen M; Lipsitch, Marc

doi:10.1016/j.epidem.2022.100620

Cited by 7 publications

(8 citation statements)

References 24 publications

(22 reference statements)

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“…Second, our results indicate that travel restrictions, especially targeted ones, are often implemented after initial imports have already come into other countries, especially for more transmissible variants, as discussed by others before 25,35 . To limit the extent of local transmission, a combination of measures are necessary to contain spread, including testing at arrival, antigen-testing before large gatherings, isolation while infectious, and vaccination, among others 36 . Lastly, as global air travel and human mobility rebound towards prepandemic levels and beyond, new variants are likely to reach secondary countries much faster, potentially before being identified by genomic surveillance.…”

Section: Discussion Limitations and Future Directionmentioning

confidence: 99%

Global Expansion of SARS-CoV-2 Variants of Concern: Dispersal Patterns and Influence of Air Travel

Tegally

Wilkinson

Martin

et al. 2022

Preprint

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In many regions of the world, the Alpha, Beta and Gamma SARS-CoV-2 Variants of Concern (VOCs) co-circulated during 2020-21 and fueled waves of infections. During 2021, these variants were almost completely displaced by the Delta variant, causing a third wave of infections worldwide. This phenomenon of global viral lineage displacement was observed again in late 2021, when the Omicron variant disseminated globally. In this study, we use phylogenetic and phylogeographic methods to reconstruct the dispersal patterns of SARS-CoV-2 VOCs worldwide. We find that the source-sink dynamics of SARS-CoV-2 varied substantially by VOC, and identify countries that acted as global hubs of variant dissemination, while other countries became regional contributors to the export of specific variants. We demonstrate a declining role of presumed origin countries of VOCs to their global dispersal: we estimate that India contributed <15% of all global exports of Delta to other countries and South Africa <1-2% of all global Omicron exports globally. We further estimate that >80 countries had received introductions of Omicron BA.1 100 days after its inferred date of emergence, compared to just over 25 countries for the Alpha variant. This increased speed of global dissemination was associated with a rebound in air travel volume prior to Omicron emergence in addition to the higher transmissibility of Omicron relative to Alpha. Our study highlights the importance of global and regional hubs in VOC dispersal, and the speed at which highly transmissible variants disseminate through these hubs, even before their detection and characterization through genomic surveillance.

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Section: Discussion Limitations and Future Directionmentioning

confidence: 99%

Global Expansion of SARS-CoV-2 Variants of Concern: Dispersal Patterns and Influence of Air Travel

Tegally

Wilkinson

Martin

et al. 2022

Preprint

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show abstract

“…If groups of only size 2 are permitted, then this simplifies to the classic SIR model, and as groups increase in size transmission becomes increasingly nonlinear with powers that sum to the group size. Transmission within groups can also yield multiple infections, i.e., superspreading (Lloyd-Smith et al, 2005) (Boyer et al, 2022).…”

Section: (Which Was Not Certified By Peer Review) Preprintmentioning

confidence: 99%

“…These focal susceptibles can be infected when attending any gathering no larger than their risk level, n ≤ k, by any attending infected with risk levels at least as large as the respective gathering size, m ≥ n. In contrast, infections among susceptibles from other subpopulations do not contribute to new focal infections and thus they function similarly to the recovered population. Overall, the transmission term is a weighted average over all gathering sizes according to a distribution, P n , set by society (e.g., by lockdowns) [4]. The risk-SIR model includes transmission heterogeneity as subpopulations with higher risk level attend a larger fraction of gatherings, homophily as subpopulations with higher risk levels preferentially interact at larger gatherings, and super-spreading as multiple infections can occur at large gatherings.…”

Section: Gathering Size Dependent Attendance: Risk-sir Modelmentioning

confidence: 99%

“…Transmission within groups can also yield multiple infections, i.e., superspreading (Lloyd-Smith et al, 2005). (Boyer et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

“…C) Denoting individuals by the maximum congregation size they are willing to attending yields the risk-SIR model. Societies can be defined by a distribution of congregation sizes which determine the epidemiological dynamics (Boyer et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

A simple model of how varying exposure at gatherings impacts the emergence of variants and their detection

Taylor

Hanage

2022

Preprint

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Understanding how epidemics spread within societies is key for establishing adequate infection control responses. Dynamical models provide a means to translate surveillance data into predictions of future disease spread, yet many epidemic models do not capture empirically observed features of socialization. Here, we utilize a connection between sampling processes and their macroscopic equations to build an epidemic model that incorporates transmission heterogeneity, homophily, and awareness of the risk of infection. Our risk-SIR model captures how diseases tend to spread initially within more social subpopulations and sequentially spread to less social subpopulations. This dynamic complicates surveillance as many metrics become dynamic when comorbidities vary with socialization. We also show fast-growing lineages that emerge within highly social subpopulations can be misidentified as potential variants of concern, and that these lineages will transiently grow in frequency as they remain distributed among more social individuals. Together, we provide a simple framework for analysis of how socialization affects disease emergence and spread, and argue that this is necessary to contextualize epidemiologic parameters like the basic and time varying reproductive numbers based on sampling and stage of the outbreak.

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Dispersal patterns and influence of air travel during the global expansion of SARS-CoV-2 variants of concern

Tegally¹,

Wilkinson²,

Tsui³

et al. 2023

Cell

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Infectious disease dynamics and restrictions on social gathering size

Cited by 7 publications

References 24 publications

Global Expansion of SARS-CoV-2 Variants of Concern: Dispersal Patterns and Influence of Air Travel

Global Expansion of SARS-CoV-2 Variants of Concern: Dispersal Patterns and Influence of Air Travel

A simple model of how varying exposure at gatherings impacts the emergence of variants and their detection

Dispersal patterns and influence of air travel during the global expansion of SARS-CoV-2 variants of concern

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