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1.
J Travel Med ; 2022 Nov 11.
Article in English | MEDLINE | ID: covidwho-2117902

ABSTRACT

BACKGROUND: Human mobility changed in unprecedented ways during the SARS-CoV-2 pandemic. In March and April 2020, when lockdowns and large travel restrictions began in most countries, global air-travel almost entirely halted (92% decrease in commercial global air travel in the months between February and April 2020). Initial recovery in global air travel started around July 2020 and subsequently nearly tripled between May and July 2021. Here, we aim to establish a preliminary link between global mobility patterns and the synchrony of SARS-CoV-2 epidemic waves across the world. METHODS: We compare epidemic peaks and human global mobility in two time periods: November 2020 to February 2021 (when just over 70 million passengers travelled), and November 2021 to February 2022 (when more than 200 million passengers travelled). We calculate the time interval during which continental epidemic peaks occurred for both of these time periods, and we calculate the pairwise correlations of epidemic waves between all pairs of countries for the same time periods. RESULTS: We find that as air travel increases at the end of 2021, epidemic peaks around the world are more synchronous with one another, both globally and regionally. Continental epidemic peaks occur globally within a 20 day interval at the end of 2021 compared to 73 days at the end of 2020, and epidemic waves globally are more correlated with one another at the end of 2021. CONCLUSIONS: This suggests that the rebound in human mobility dictates the synchrony of global and regional epidemic waves. In line with theoretical work, we show that in a more connected world, epidemic dynamics are more synchronized.

2.
Nature ; 610(7930): 154-160, 2022 10.
Article in English | MEDLINE | ID: covidwho-1991629

ABSTRACT

The SARS-CoV-2 Delta (Pango lineage B.1.617.2) variant of concern spread globally, causing resurgences of COVID-19 worldwide1,2. The emergence of the Delta variant in the UK occurred on the background of a heterogeneous landscape of immunity and relaxation of non-pharmaceutical interventions. Here we analyse 52,992 SARS-CoV-2 genomes from England together with 93,649 genomes from the rest of the world to reconstruct the emergence of Delta and quantify its introduction to and regional dissemination across England in the context of changing travel and social restrictions. Using analysis of human movement, contact tracing and virus genomic data, we find that the geographic focus of the expansion of Delta shifted from India to a more global pattern in early May 2021. In England, Delta lineages were introduced more than 1,000 times and spread nationally as non-pharmaceutical interventions were relaxed. We find that hotel quarantine for travellers reduced onward transmission from importations; however, the transmission chains that later dominated the Delta wave in England were seeded before travel restrictions were introduced. Increasing inter-regional travel within England drove the nationwide dissemination of Delta, with some cities receiving more than 2,000 observable lineage introductions from elsewhere. Subsequently, increased levels of local population mixing-and not the number of importations-were associated with the faster relative spread of Delta. The invasion dynamics of Delta depended on spatial heterogeneity in contact patterns, and our findings will inform optimal spatial interventions to reduce the transmission of current and future variants of concern, such as Omicron (Pango lineage B.1.1.529).


Subject(s)
COVID-19 , SARS-CoV-2 , COVID-19/epidemiology , COVID-19/prevention & control , COVID-19/transmission , COVID-19/virology , Cities/epidemiology , Contact Tracing , England/epidemiology , Genome, Viral/genetics , Humans , Quarantine/legislation & jurisprudence , SARS-CoV-2/genetics , SARS-CoV-2/growth & development , SARS-CoV-2/isolation & purification , Travel/legislation & jurisprudence
4.
Nat Commun ; 12(1): 5769, 2021 10 01.
Article in English | MEDLINE | ID: covidwho-1447305

ABSTRACT

Distinct SARS-CoV-2 lineages, discovered through various genomic surveillance initiatives, have emerged during the pandemic following unprecedented reductions in worldwide human mobility. We here describe a SARS-CoV-2 lineage - designated B.1.620 - discovered in Lithuania and carrying many mutations and deletions in the spike protein shared with widespread variants of concern (VOCs), including E484K, S477N and deletions HV69Δ, Y144Δ, and LLA241/243Δ. As well as documenting the suite of mutations this lineage carries, we also describe its potential to be resistant to neutralising antibodies, accompanying travel histories for a subset of European cases, evidence of local B.1.620 transmission in Europe with a focus on Lithuania, and significance of its prevalence in Central Africa owing to recent genome sequencing efforts there. We make a case for its likely Central African origin using advanced phylogeographic inference methodologies incorporating recorded travel histories of infected travellers.


Subject(s)
COVID-19/transmission , COVID-19/virology , SARS-CoV-2/genetics , Africa, Central/epidemiology , Antibodies, Neutralizing/immunology , COVID-19/epidemiology , Europe/epidemiology , Humans , Immune Evasion/genetics , Mutation , Phylogeny , Phylogeography , SARS-CoV-2/classification , SARS-CoV-2/immunology , Spike Glycoprotein, Coronavirus/genetics , Travel/statistics & numerical data
5.
J Travel Med ; 27(2)2020 03 13.
Article in English | MEDLINE | ID: covidwho-1335914

ABSTRACT

There is currently an outbreak of pneumonia of unknown aetiology in Wuhan, China. Although there are still several unanswered questions about this infection, we evaluate the potential for international dissemination of this disease via commercial air travel should the outbreak continue.


Subject(s)
Air Travel , Betacoronavirus/isolation & purification , Coronavirus Infections/transmission , Pneumonia, Viral/transmission , Animals , Betacoronavirus/genetics , COVID-19 , China/epidemiology , Contact Tracing , Coronavirus Infections/epidemiology , Coronavirus Infections/virology , Humans , Pneumonia, Viral/epidemiology , Pneumonia, Viral/virology , Public Health , SARS-CoV-2 , Zoonoses
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