Estimating the establishment of local transmission and the cryptic phase of the COVID-19 pandemic in the USA

AbstractMotivated by the rapid spread of a novel coronavirus (2019-nCoV) in Mainland China, we use a global metapopulation disease transmission model to project the impact of both domestic and international travel limitations on the national and international spread of the epidemic. The model is calibrated on the evidence of internationally imported cases before the implementation of the travel quarantine of Wuhan. By assuming a generation time of 7.5 days, the reproduction number is estimated to be 2.4 [90% CI 2.2-2.6]. The median estimate for number of cases before the travel ban implementation on January 23, 2020 is 58,956 [90% CI 40,759 - 87,471] in Wuhan and 3,491 [90% CI 1,924 - 7,360] in other locations in Mainland China. The model shows that as of January 23, most Chinese cities had already received a considerable number of infected cases, and the travel quarantine delays the overall epidemic progression by only 3 to 5 days. The travel quarantine has a more marked effect at the international scale, where we estimate the number of case importations to be reduced by 80% until the end of February. Modeling results also indicate that sustained 90% travel restrictions to and from Mainland China only modestly affect the epidemic trajectory unless combined with a 50% or higher reduction of transmission in the community.

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Uncovering two phases of early intercontinental COVID-19 transmission dynamics

Journal of Travel Medicine ◽

10.1093/jtm/taaa200 ◽

2020 ◽

Vol 27 (8) ◽

Author(s):

Jing Yang ◽

Juan Li ◽

Shengjie Lai ◽

Corrine W Ruktanonchai ◽

Weijia Xing ◽

...

Keyword(s):

Phylogenetic Analyses ◽

International Travel ◽

Contact Tracing ◽

Genetic Sequencing ◽

Response Strategies ◽

The World ◽

Containment Measures ◽

The Usa ◽

Community Transmission ◽

Two Phases

Abstract Background The COVID-19 pandemic has posed an ongoing global crisis, but how the virus spread across the world remains poorly understood. This is of vital importance for informing current and future pandemic response strategies. Methods We performed two independent analyses, travel network-based epidemiological modelling and Bayesian phylogeographic inference, to investigate the intercontinental spread of COVID-19. Results Both approaches revealed two distinct phases of COVID-19 spread by the end of March 2020. In the first phase, COVID-19 largely circulated in China during mid-to-late January 2020 and was interrupted by containment measures in China. In the second and predominant phase extending from late February to mid-March, unrestricted movements between countries outside of China facilitated intercontinental spread, with Europe as a major source. Phylogenetic analyses also revealed that the dominant strains circulating in the USA were introduced from Europe. However, stringent restrictions on international travel across the world since late March have substantially reduced intercontinental transmission. Conclusions Our analyses highlight that heterogeneities in international travel have shaped the spatiotemporal characteristics of the pandemic. Unrestricted travel caused a large number of COVID-19 exportations from Europe to other continents between late February and mid-March, which facilitated the COVID-19 pandemic. Targeted restrictions on international travel from countries with widespread community transmission, together with improved capacity in testing, genetic sequencing and contact tracing, can inform timely strategies for mitigating and containing ongoing and future waves of COVID-19 pandemic.

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ЮНВТО Всемирная туристская Барометр, и статистическое приложение Обновленная информация, ИСентябрь 2021 года

Барометр меҗдународного туризма ЮНВТО ◽

10.18111/wtobarometerrus.2021.19.1.5 ◽

2021 ◽

Vol 19 (5) ◽

pp. 1-40

Keyword(s):

The United States ◽

International Travel ◽

International Tourism ◽

Modest Improvement ◽

International Tourist ◽

The Pacific ◽

Travel Restrictions ◽

Low Levels ◽

Roll Out ◽

Made In

International tourism shows slight recovery in June and July 2021 driven by vaccinations and border reopening International tourist arrivals (overnight visitors) in the first seven months of 2021 were 40% below the levels of 2020, and still 80% down when compared to the same period of pre-pandemic year 2019. After a weak start of the year, international tourism saw a modest improvement during the months of June and July 2021. The small improvement in June and July was underpinned by the reopening of many destinations to international travel, mostly in Europe and the Americas. The relaxation of travel restrictions to vaccinated travellers, coupled with progress made in the roll-out of COVID-19 vaccines, contributed to ease travel restrictions, lift consumer confidence and gradually restore safe mobility in Europe and other parts of the world. Small islands in the Caribbean, Africa, and Asia and the Pacific, together with a few small European destinations recorded the best performance in June and July, with arrivals coming close to, or sometimes exceeding pre-pandemic levels. July (-67%) saw comparatively better performance than June (-77%), making it the best month so far since April 2020. Asia and the Pacific continued to suffer the weakest results in January-July 2021, with a 95% drop in international arrivals compared to the same period in 2019. The Middle East (-82%) recorded the second largest decline, followed by Europe and Africa (both -77%). The Americas (-68%) saw a comparatively smaller decrease. Although destinations continued to report very weak international tourism revenues in the first seven months of 2021, several countries recorded a modest improvement in the months of June and July, and some even surpassed the earnings of 2019. The same is true for outbound travel. Among the larger source markets, France (-35% over 2019) and the United States (-49%) saw a small rebound in expenditure in July. Despite the relative improvement over the low levels of 2020, international tourism remained well below 2019 levels. This is also reflected in the evaluation made by the UNWTO Panel of Experts in the September survey, showing mixed results for the period May-August 2021. Looking ahead, most experts continue to expect a rebound in 2022, driven by unleashed pent-up demand, mostly during the second and third quarter of that year. Nearly one-third of respondents expect a potential rebound in 2023. Almost half of all experts continue to see a return of international arrivals to 2019 levels in 2024 or later.

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UNWTO World Tourism Barometer and Statistical Annex, October 2020

UNWTO World Tourism Barometer ◽

10.18111/wtobarometereng.2020.18.1.6 ◽

2020 ◽

Vol 18 (6) ◽

pp. 1-36 ◽

Cited By ~ 3

Keyword(s):

The United States ◽

International Travel ◽

International Tourism ◽

The European Union ◽

International Tourist ◽

The Pacific ◽

Slow Virus ◽

Travel Restrictions ◽

Main Barrier ◽

The Impact

International travel plunges 70% in the first eight months of 2020 International tourist arrivals (overnight visitors) declined 70% in the first eight months of 2020 over the same period of last year, amid global travel restrictions including many borders fully closed, to contain the ongoing COVID-19 pandemic. International arrivals plunged 81% in July and 79% in August, traditionally the two busiest months of the year and the peak of the Northern Hemisphere summer season. Despite such large declines, this represents a relative improvement over the 90% or greater decreases of the previous months, as some destinations started to reopen to international tourism, mostly in the European Union. The decline in January-August 2020 represents 700 million fewer international tourist arrivals compared to the same period in 2019, and translates into a loss of US$ 730 billion in export revenues from international tourism, more than 8 times the loss in 2009 under the impact of the global economic crisis. Asia and the Pacific, the first region to suffer the impact of the pandemic, saw a 79% decrease in arrivals in January-August 2020. Africa and the Middle East both recorded a 69% drop this eight-month period, while Europe saw a 68% decline and the Americas 65%. Data on international tourism expenditure continues to reflect very weak demand for outbound travel, though in several large markets such as the United States, Germany and Italy there is a small uptick in spending in the months of July and August. Based on latest trends, a 75% decrease in international arrivals is estimated for the month of September and a drop of close to 70% for the whole of 2020. While demand for international travel remains subdued, domestic tourism is strengthening recovery in several large markets such as China and Russia. The UNWTO Confidence Index continues at record lows. Most UNWTO Panel Experts expect a rebound in international tourism by the third quarter of 2021 and a return to pre-pandemic 2019 levels not before 2023. Experts consider travel restrictions as the main barrier weighing on the recovery of international tourism, along with slow virus containment and low consumer confidence.

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Early introductions and community transmission of SARS-CoV-2 variant B.1.1.7 in the United States

10.1101/2021.02.10.21251540 ◽

2021 ◽

Author(s):

Tara Alpert ◽

Erica Lasek-Nesselquist ◽

Anderson F. Brito ◽

Andrew L. Valesano ◽

Jessica Rothman ◽

...

Keyword(s):

Public Health ◽

United States ◽

New York ◽

Diagnostic Testing ◽

The United States ◽

International Travel ◽

Health Concern ◽

Public Health Response ◽

Community Transmission ◽

The Uk

SummaryThe emergence and spread of SARS-CoV-2 lineage B.1.1.7, first detected in the United Kingdom, has become a national public health concern in the United States because of its increased transmissibility. Over 500 COVID-19 cases associated with this variant have been detected since December 2020, but its local establishment and pathways of spread are relatively unknown. Using travel, genomic, and diagnostic testing data, we highlight the primary ports of entry for B.1.1.7 in the US and locations of possible underreporting of B.1.1.7 cases. New York, which receives the most international travel from the UK, is likely one of the key hubs for introductions and domestic spread. Finally, we provide evidence for increased community transmission in several states. Thus, genomic surveillance for B.1.1.7 and other variants urgently needs to be enhanced to better inform the public health response.

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Barómetro OMT del Turismo Mundial y anexo estadístico, septiembre 2021

Barómetro OMT del Turismo Mundial ◽

10.18111/wtobarometeresp.2021.19.1.5 ◽

2021 ◽

Vol 19 (5) ◽

pp. 1-40

Keyword(s):

The United States ◽

International Travel ◽

International Tourism ◽

Modest Improvement ◽

International Tourist ◽

The Pacific ◽

Travel Restrictions ◽

Low Levels ◽

Roll Out ◽

Made In

International tourism shows slight recovery in June and July 2021 driven by vaccinations and border reopening International tourist arrivals (overnight visitors) in the first seven months of 2021 were 40% below the levels of 2020, and still 80% down when compared to the same period of pre-pandemic year 2019. After a weak start of the year, international tourism saw a modest improvement during the months of June and July 2021. The small improvement in June and July was underpinned by the reopening of many destinations to international travel, mostly in Europe and the Americas. The relaxation of travel restrictions to vaccinated travellers, coupled with progress made in the roll-out of COVID-19 vaccines, contributed to ease travel restrictions, lift consumer confidence and gradually restore safe mobility in Europe and other parts of the world. Small islands in the Caribbean, Africa, and Asia and the Pacific, together with a few small European destinations recorded the best performance in June and July, with arrivals coming close to, or sometimes exceeding pre-pandemic levels. July (-67%) saw comparatively better performance than June (-77%), making it the best month so far since April 2020. Asia and the Pacific continued to suffer the weakest results in January-July 2021, with a 95% drop in international arrivals compared to the same period in 2019. The Middle East (-82%) recorded the second largest decline, followed by Europe and Africa (both -77%). The Americas (-68%) saw a comparatively smaller decrease. Although destinations continued to report very weak international tourism revenues in the first seven months of 2021, several countries recorded a modest improvement in the months of June and July, and some even surpassed the earnings of 2019. The same is true for outbound travel. Among the larger source markets, France (-35% over 2019) and the United States (-49%) saw a small rebound in expenditure in July. Despite the relative improvement over the low levels of 2020, international tourism remained well below 2019 levels. This is also reflected in the evaluation made by the UNWTO Panel of Experts in the September survey, showing mixed results for the period May-August 2021. Looking ahead, most experts continue to expect a rebound in 2022, driven by unleashed pent-up demand, mostly during the second and third quarter of that year. Nearly one-third of respondents expect a potential rebound in 2023. Almost half of all experts continue to see a return of international arrivals to 2019 levels in 2024 or later.

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Cryptic transmission of SARS-CoV-2 and the first COVID-19 wave in Europe and the United States

10.1101/2021.03.24.21254199 ◽

2021 ◽

Author(s):

Jessica T Davis ◽

Matteo Chinazzi ◽

Nicola Perra ◽

Kunpeng Mu ◽

Ana Pastore y Piontti ◽

...

Keyword(s):

United States ◽

Early Stage ◽

The United States ◽

International Travel ◽

Surveillance Systems ◽

Model Driven ◽

Global Dynamic ◽

The Us ◽

Community Transmission ◽

Spatio Temporal

Given the narrowness of the initial testing criteria, the SARS-CoV-2 virus spread through cryptic transmission in January and February, setting the stage for the epidemic wave experienced in March and April, 2020. We use a global metapopulation epidemic model to provide a mechanistic understanding of the global dynamic underlying the establishment of the COVID-19 pandemic in Europe and the United States (US). The model is calibrated on international case introductions at the early stage of the pandemic. We find that widespread community transmission of SARS-CoV-2 was likely in several areas of Europe and the US by January 2020, and estimate that by early March, only 1-3 in 100 SARS-CoV-2 infections were detected by surveillance systems. Modeling results indicate international travel as the key driver of the introduction of SARS-CoV-2 with possible importation and transmission events as early as December, 2019. We characterize the resulting heterogeneous spatio-temporal spread of SARS-CoV-2 and the burden of the first COVID-19 wave (February-July 2020). We estimate infection attack rates ranging from 0.78%-15.2% in the US and 0.19%-13.2% in Europe. The spatial modeling of SARS-CoV-2 introductions and spreading provides insights into the design of innovative, model-driven surveillance systems and preparedness plans that have a broader initial capacity and indication for testing.

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ЮНВТО Всемирная туристская Барометр, и статистическое приложение Обновленная информация, Декабрь 2020 года

Барометр меҗдународного туризма ЮНВТО ◽

10.18111/wtobarometerrus.2020.18.1.7 ◽

2020 ◽

Vol 18 (7) ◽

pp. 1-36

Keyword(s):

Travel Demand ◽

Economic Loss ◽

The United States ◽

International Travel ◽

International Tourism ◽

Current Trends ◽

International Tourist ◽

The Pacific ◽

Travel Restrictions ◽

The Impact

International tourism expected to decline over 70% in 2020, back to levels of 30 years ago International tourist arrivals (overnight visitors) fell by 72% in January-October 2020 over the same period last year, curbed by slow virus containment, low traveller confidence and important restrictions on travel still in place, due to the COVID-19 pandemic. The decline in the first ten months of the year represents 900 million fewer international tourist arrivals compared to the same period in 2019, and translates into a loss of US$ 935 billion in export revenues from international tourism, more than 10 times the loss in 2009 under the impact of the global economic crisis. Asia and the Pacific saw an 82% decrease in arrivals in January-October 2020. The Middle East recorded a 73% decline, while Africa saw a 69% drop this ten-month period. International arrivals in both Europe and the Americas declined by 68%. Data on international tourism expenditure continues to reflect very weak demand for outbound travel. However, some large markets such as the United States, Germany and France have shown some shy signs of recovery in the recent months. While demand for international travel remains subdued, domestic tourism continues to grow in several large markets such as China and Russia, where domestic air travel demand has mostly returned to pre-COVID levels. Based on current trends, UNWTO expects international arrivals to decline by 70% to 75% for the whole of 2020. This would mean that international tourism could have returned to levels of 30 years ago. The estimated decline in internationals tourism in 2020 is equivalent to a loss of about 1 billion arrivals and US$ 1.1 trillion in international tourism receipts. This plunge in international tourism could result in an estimated economic loss of over US$ 2 trillion in global GDP, more than 2% of the world’s GDP in 2019. Looking ahead, the announcement and the roll-out of a vaccine are expected to gradually increase consumer confidence and contribute to ease travel restrictions. UNWTO’s extended scenarios for 2021-2024 point to a rebound in international tourism by the second half of 2021. Nonetheless, a return to 2019 levels in terms of international arrivals could take 2½ to 4 years.

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Coast-to-coast spread of SARS-CoV-2 in the United States revealed by genomic epidemiology

10.1101/2020.03.25.20043828 ◽

2020 ◽

Cited By ~ 12

Author(s):

Joseph R. Fauver ◽

Mary E. Petrone ◽

Emma B. Hodcroft ◽

Kayoko Shioda ◽

Hanna Y. Ehrlich ◽

...

Keyword(s):

United States ◽

Pacific Northwest ◽

The United States ◽

International Travel ◽

Viral Genomes ◽

Genomic Epidemiology ◽

The Pacific ◽

Travel Restrictions ◽

Novel Coronavirus ◽

The U.S

SummarySince its emergence and detection in Wuhan, China in late 2019, the novel coronavirus SARS-CoV-2 has spread to nearly every country around the world, resulting in hundreds of thousands of infections to date. The virus was first detected in the Pacific Northwest region of the United States in January, 2020, with subsequent COVID-19 outbreaks detected in all 50 states by early March. To uncover the sources of SARS-CoV-2 introductions and patterns of spread within the U.S., we sequenced nine viral genomes from early reported COVID-19 patients in Connecticut. Our phylogenetic analysis places the majority of these genomes with viruses sequenced from Washington state. By coupling our genomic data with domestic and international travel patterns, we show that early SARS-CoV-2 transmission in Connecticut was likely driven by domestic introductions. Moreover, the risk of domestic importation to Connecticut exceeded that of international importation by mid-March regardless of our estimated impacts of federal travel restrictions. This study provides evidence for widespread, sustained transmission of SARS-CoV-2 within the U.S. and highlights the critical need for local surveillance.

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A Genomic Survey of SARS-CoV-2 Reveals Multiple Introductions into Northern California without a Predominant Lineage

10.1101/2020.03.27.20044925 ◽

2020 ◽

Cited By ~ 14

Author(s):

Xianding Deng ◽

Wei Gu ◽

Scot Federman ◽

Louis du Plessis ◽

Oliver G. Pybus ◽

...

Keyword(s):

Phylogenetic Analyses ◽

The United States ◽

Contact Tracing ◽

Northern California ◽

Cruise Ship ◽

Multiple Introductions ◽

Genomic Epidemiology ◽

The Usa ◽

Community Transmission ◽

Virus Genomes

AbstractThe COVID-19 pandemic caused by the novel coronavirus SARS-CoV-2 has spread globally, resulting in >300,000 reported cases worldwide as of March 21st, 2020. Here we investigate the genetic diversity and genomic epidemiology of SARS-CoV-2 in Northern California using samples from returning travelers, cruise ship passengers, and cases of community transmission with unclear infection sources. Virus genomes were sampled from 29 patients diagnosed with COVID-19 infection from Feb 3rd through Mar 15th. Phylogenetic analyses revealed at least 8 different SARS-CoV-2 lineages, suggesting multiple independent introductions of the virus into the state. Virus genomes from passengers on two consecutive excursions of the Grand Princess cruise ship clustered with those from an established epidemic in Washington State, including the WA1 genome representing the first reported case in the United States on January 19th. We also detected evidence for presumptive transmission of SARS-CoV-2 lineages from one community to another. These findings suggest that cryptic transmission of SARS-CoV-2 in Northern California to date is characterized by multiple transmission chains that originate via distinct introductions from international and interstate travel, rather than widespread community transmission of a single predominant lineage. Rapid testing and contact tracing, social distancing, and travel restrictions are measures that will help to slow SARS-CoV-2 spread in California and other regions of the USA.

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