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

The Alpha, Beta, and Gamma SARS-CoV-2 variants of concern (VOCs) co-circulated globally during 2020 and 2021, fueling waves of infections. They were displaced by Delta during a third wave worldwide in 2021, which, in turn, was displaced by Omicron in late 2021. In this study, we use phylogenetic and phylogeographic methods to reconstruct the dispersal patterns of VOCs worldwide. We find that source-sink dynamics varied substantially by VOC and identify countries that acted as global and regional hubs of dissemination. We demonstrate the declining role of presumed origin countries of VOCs in their global dispersal, estimating that India contributed <15% of Delta exports and South Africa <1%-2% of Omicron dispersal. We estimate that >80 countries had received introductions of Omicron within 100 days of its emergence, associated with accelerated passenger air travel and higher transmissibility. Our study highlights the rapid dispersal of highly transmissible variants, with implications for genomic surveillance along the hierarchical airline network.

Cryptic transmission of SARS-CoV-2 and the first COVID-19 wave.

Considerable uncertainty surrounds the timeline of introductions and onsets of local transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) globally1-7. Although a limited number of SARS-CoV-2 introductions were reported in January and February 2020 (refs.8,9), the narrowness of the initial testing criteria, combined with a slow growth in testing capacity and porous travel screening10, left many countries vulnerable to unmitigated, cryptic transmission. Here we use a global metapopulation epidemic model to provide a mechanistic understanding of the early dispersal of infections and the temporal windows of the introduction of SARS-CoV-2 and onset of local transmission in Europe and the USA. We find that community transmission of SARS-CoV-2 was likely to have been present in several areas of Europe and the USA by January 2020, and estimate that by early March, only 1 to 4 in 100 SARS-CoV-2 infections were detected by surveillance systems. The modelling results highlight international travel as the key driver of the introduction of SARS-CoV-2, with possible introductions and transmission events as early as December 2019 to January 2020. We find a heterogeneous geographic distribution of cumulative infection attack rates by 4 July 2020, ranging from 0.78% to 15.2% across US states and 0.19% to 13.2% in European countries. Our approach complements phylogenetic analyses and other surveillance approaches and provides insights that can be used to design innovative, model-driven surveillance systems that guide enhanced testing and response strategies.

How to avoid a local epidemic becoming a global pandemic.

Here, we combine international air travel passenger data with a standard epidemiological model of the initial 3 mo of the COVID-19 pandemic (January through March 2020; toward the end of which the entire world locked down). Using the information available during this initial phase of the pandemic, our model accurately describes the main features of the actual global development of the pandemic demonstrated by the high degree of coherence between the model and global data. The validated model allows for an exploration of alternative policy efficacies (reducing air travel and/or introducing different degrees of compulsory immigration quarantine upon arrival to a country) in delaying the global spread of SARS-CoV-2 and thus is suggestive of similar efficacy in anticipating the spread of future global disease outbreaks. We show that a lesson from the recent pandemic is that reducing air travel globally is more effective in reducing the global spread than adopting immigration quarantine. Reducing air travel out of a source country has the most important effect regarding the spreading of the disease to the rest of the world. Based upon our results, we propose a digital twin as a further developed tool to inform future pandemic decision-making to inform measures intended to control the spread of disease agents of potential future pandemics. We discuss the design criteria for such a digital twin model as well as the feasibility of obtaining access to the necessary online data on international air travel.

COVID-19 passenger screening to reduce travel risk and translocation of disease.

Aviation passenger screening has been used worldwide to mitigate the translocation risk of SARS-CoV-2. We present a model that evaluates factors in screening strategies used in air travel and assess their relative sensitivity and importance in identifying infectious passengers. We use adapted Monte Carlo simulations to produce hypothetical disease timelines for the Omicron variant of SARS-CoV-2 for travelling passengers. Screening strategy factors assessed include having one or two RT-PCR and/or antigen tests prior to departure and/or post-arrival, and quarantine length and compliance upon arrival. One or more post-arrival tests and high quarantine compliance were the most important factors in reducing pathogen translocation. Screening that combines quarantine and post-arrival testing can shorten the length of quarantine for travelers, and variability and mean testing sensitivity in post-arrival RT-PCR and antigen tests decrease and increase with the greater time between the first and second post-arrival test, respectively. This study provides insight into the role various screening strategy factors have in preventing the translocation of infectious diseases and a flexible framework adaptable to other existing or emerging diseases. Such findings may help in public health policy and decision-making in present and future evidence-based practices for passenger screening and pandemic preparedness.

A methodology for estimating SARS-CoV-2 importation risk by air travel into Canada between July and November 2021.

BACKGROUND: Estimating rates of disease importation by travellers is a key activity to assess both the risk to a country from an infectious disease emerging elsewhere in the world and the effectiveness of border measures. We describe a model used to estimate the number of travellers infected with SARS-CoV-2 into Canadian airports in 2021, and assess the impact of pre-departure testing requirements on importation risk. METHODS: A mathematical model estimated the number of essential and non-essential air travellers infected with SARS-CoV-2, with the latter requiring a negative pre-departure test result. The number of travellers arriving infected (i.e. imported cases) depended on air travel volumes, SARS-CoV-2 exposure risk in the departure country, prior infection or vaccine acquired immunity, and, for non-essential travellers, screening from pre-departure molecular testing. Importation risk was estimated weekly from July to November 2021 as the number of imported cases and percent positivity (PP; i.e. imported cases normalised by travel volume). The impact of pre-departure testing was assessed by comparing three scenarios: baseline (pre-departure testing of all non-essential travellers; most probable importation risk given the pre-departure testing requirements), counterfactual scenario 1 (no pre-departure testing of fully vaccinated non-essential travellers), and counterfactual scenario 2 (no pre-departure testing of non-essential travellers). RESULTS: In the baseline scenario, weekly imported cases and PP varied over time, ranging from 145 to 539 cases and 0.15 to 0.28%, respectively. Most cases arrived from the USA, Mexico, the United Kingdom, and France. While modelling suggested that essential travellers had a higher weekly PP (0.37 - 0.65%) than non-essential travellers (0.12 - 0.24%), they contributed fewer weekly cases (62 - 154) than non-essential travellers (84 - 398 per week) given their lower travel volume. Pre-departure testing was estimated to reduce imported cases by one third (counterfactual scenario 1) to one half (counterfactual scenario 2). CONCLUSIONS: The model results highlighted the weekly variation in importation by traveller group (e.g., reason for travel and country of departure) and enabled a framework for measuring the impact of pre-departure testing requirements. Quantifying the contributors of importation risk through mathematical simulation can support the design of appropriate public health policy on border measures.

The potential stickiness of pandemic-induced behavior changes in the United States.

Human behavior is notoriously difficult to change, but a disruption of the magnitude of the COVID-19 pandemic has the potential to bring about long-term behavioral changes. During the pandemic, people have been forced to experience new ways of interacting, working, learning, shopping, traveling, and eating meals. A critical question going forward is how these experiences have actually changed preferences and habits in ways that might persist after the pandemic ends. Many observers have suggested theories about what the future will bring, but concrete evidence has been lacking. We present evidence on how much US adults expect their own postpandemic choices to differ from their prepandemic lifestyles in the areas of telecommuting, restaurant patronage, air travel, online shopping, transit use, car commuting, uptake of walking and biking, and home location. The analysis is based on a nationally representative survey dataset collected between July and October 2020. Key findings include that the "new normal" will feature a doubling of telecommuting, reduced air travel, and improved quality of life for some.

Splenic Subcapsular Hematoma from Commercial Air Travel: Case Report of a Unique Incident of Altitude-Associated Splenic Syndrome.

BACKGROUND: Sickle cell trait (SCT), the heterozygous form of sickle cell disease, is generally thought of as a benign condition. However, it is possible for those with SCT to have serious complications, especially when they are exposed to high altitudes where oxygen levels are low. CASE REPORT: We present a case of a 41-year-old man with a history of SCT who developed severe epigastric pain and nearly lost consciousness while traveling on a commercial airplane. His twin brother, who also has SCT, had a similar episode in the past and required a splenectomy. A splenic subcapsular hematoma was found in a computed tomography scan of the abdomen and pelvis with intravenous contrast. He was admitted and managed conservatively until his symptoms resolved. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Though SCT is prevalent in our population, the complications that can arise, such as altitude-associated splenic syndrome, have likely not been thoroughly investigated. Physicians should add this condition to their differential if they practice at locations near airports or in areas of higher altitude and if their patients have a past medical history of SCT.

Effect of Predeparture Testing on Postarrival SARS-CoV-2-Positive Test Results Among International Travelers - CDC Traveler-Based Genomic Surveillance Program, Four U.S. Airports, March-September 2022.

Beginning December 6, 2021, all international air passengers boarding flights to the United States were required to show either a negative result from a SARS-CoV-2 viral test taken ≤1 day before departure or proof of recovery from COVID-19 within the preceding 90 days (1). As of June 12, 2022, predeparture testing was no longer mandatory but remained recommended by CDC (2,3). Various modeling studies have estimated that predeparture testing the day before or the day of air travel reduces transmission or importation of SARS-CoV-2 by 31%-76% (4-7). Postarrival SARS-CoV-2 pooled testing data from CDC's Traveler-based Genomic Surveillance program were used to compare SARS-CoV-2 test results among volunteer travelers arriving at four U.S. airports during two 12-week periods: March 20-June 11, 2022, when predeparture testing was required, and June 12-September 3, 2022, when predeparture testing was not required. In a multivariable logistic regression model, pooled nasal swab specimens collected during March 20-June 11 were 52% less likely to be positive for SARS-CoV-2 than were those collected during June 12-September 3, after adjusting for COVID-19 incidence in the flight's country of origin, sample pool size, and collection airport (adjusted odds ratio [aOR] = 0.48, 95% CI = 0.39-0.58) (p<0.001). These findings support predeparture testing as a tool for reducing travel-associated SARS-CoV-2 transmission and provide important real-world evidence that can guide decisions for future outbreaks and pandemics.

Comparative analysis of inflight transmission of SARS-CoV-2, influenza, and SARS-CoV-1.

The aim of this study is to evaluate the infection risk of aircraft passengers seated within and beyond two rows of the index case(s) of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), influenza A(H1N1)pdm09 virus, and SARS-CoV-1. PubMed databases were searched for articles containing information on air travel-related transmission of SARS-CoV-2, influenza A(H1N1)pdm09 virus, and SARS-CoV-1 infections. We performed a meta-analysis of inflight infection data. In the eight flights where the attack rate could be calculated, the inflight SARS-CoV-2 attack rates ranged from 2.6% to 16.1%. The risk ratios of infection for passengers seated within and outside the two rows of the index cases were 5.64 (95% confidence interval (CI):1.94-16.40) in SARS-CoV-2 outbreaks, 4.26 (95% CI:1.08-16.81) in the influenza A(H1N1)pdm09 virus outbreaks, and 1.91 (95% CI:0.80-4.55) in SARS-CoV-1 outbreaks. Furthermore, we found no significant difference between the attack rates of SARS-CoV-2 in flights where the passengers were wearing masks and those where they were not (p = 0.22). The spatial distribution of inflight SARS-CoV-2 outbreaks was more similar to that of the influenza A(H1N1)pdm09 virus outbreaks than to that of SARS-CoV-1. Given the high proportion of asymptomatic or pre-symptomatic infection in SARS-CoV-2 transmission, we hypothesised that the proximity transmission, especially short-range airborne route, might play an important role in the inflight SARS-CoV-2 transmission.

Infrared image method for possible COVID-19 detection through febrile and subfebrile people screening.

This study proposed an infrared image-based method for febrile and subfebrile people screening to comply with the society need for alternative, quick response, and effective methods for COVID-19 contagious people screening. The methodology consisted of: (i) Developing a method based on facial infrared imaging for possible COVID-19 early detection in people with and without fever (subfebrile state); (ii) Using 1206 emergency room (ER) patients to develop an algorithm for general application of the method, and (iii) Testing the method and algorithm effectiveness in 2558 cases (RT-qPCR tested for COVID-19) from 227,261 workers evaluations in five different countries. Artificial intelligence was used through a convolutional neural network (CNN) to develop the algorithm that took facial infrared images as input and classified the tested individuals in three groups: fever (high risk), subfebrile (medium risk), and no fever (low risk). The results showed that suspicious and confirmed COVID-19 (+) cases characterized by temperatures below the 37.5 °C fever threshold were identified. Also, average forehead and eye temperatures greater than 37.5 °C were not enough to detect fever similarly to the proposed CNN algorithm. Most RT-qPCR confirmed COVID-19 (+) cases found in the 2558 cases sample (17 cases/89.5%) belonged to the CNN selected subfebrile group. The COVID-19 (+) main risk factor was to be in the subfebrile group, in comparison to age, diabetes, high blood pressure, smoking and others. In sum, the proposed method was shown to be a potentially important new tool for COVID-19 (+) people screening for air travel and public places in general.

Sensitive SARS-CoV-2 detection, air travel Covid-19 testing, variant determination and fast direct PCR detection, using ddPCR and RT-qPCR methods.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) monitoring in air traffic is important in the prevention of the virus spreading from abroad. The gold standard for SARS-CoV-2 detection is RT-qPCR; however, for early and low viral load detection, a much more sensitive method, such as droplet digital PCR (ddPCR), is required. Our first step was to developed both, ddPCR and RT-qPCR methods, for sensitive SARS-CoV-2 detection. Analysis of ten swab/saliva samples of five Covid-19 patients in different stages of disease showed positivity in 6/10 samples with RT-qPCR and 9/10 with ddPCR. We also used our RT-qPCR method for SARS-CoV-2 detection without the need of RNA extraction, obtaining results in 90-120 minutes. We analyzed 116 self-collected saliva samples from passengers and airport staff arriving from abroad. All samples were negative by RT-qPCR, while 1 was positive, using ddPCR. Lastly, we developed ddPCR assays for SARS-CoV-2 variants identification (alpha, beta, gamma, delta/kappa) that are more economically advantageous when compared to NGS. Our findings demonstrated that saliva samples can be stored at ambient temperature, as we did not observe any significant difference between a fresh sample and the same sample after 24 hours (p = 0.23), hence, saliva collection is the optimal route for sampling airplane passengers. Our results also showed that droplet digital PCR is a more suitable method for detecting virus from saliva, compared to RT-qPCR. Keywords: COVID-19; RT-PCR; ddPCR; SARS-CoV-2; nasopharyngeal swab; saliva.

When Is Air Travel Safe after Mild Traumatic Brain Injury/Sports-Related Concussion?

ABSTRACT: While the literature regarding return to play and recovery protocols from mild traumatic brain injury (mTBI) and sports-related concussions (SRC) is growing, there continues to be a paucity of data regarding when air travel is safe for athletes after sustaining certain brain injuries, such as mTBI and SRC. Although it is known hypoxia can negatively affect severe TBI patients, it is unclear whether mild hypoxia, which may be experienced during commercial air travel, is clinically significant for athletes who have recently sustained mTBI injuries. Further research is required to provide more standardized recommendations on when air travel is safe. With the current available literature, clinicians still need to weigh the evidence, consider how it applies to each individual patient, and engage in shared decision making to ultimately decide what is best for the patient.

Perioperative air travel increases the risk of venous thromboembolism following lower limb arthroplasty.

PURPOSE: Venous thromboembolism (VTE) is a significant complication following lower limb arthroplasty (LLA). There is a paucity of evidence with regard to air travel following LLA. Orthopaedic surgeons are often asked by patients regarding air travel following LLA, and there is a need for evidence to guide these patients. METHODS: This was a retrospective cohort study. We identified two cohorts, one travelling to and from the hospital by air and another, by land. All patients received routine preoperative and post-operative care, and thromboprophylaxis, as per our hospital guidelines. We collected baseline demographics, ASA score and incidence of VTE at 90 days using local patient records and a national joint registry. We also recorded data on flight time and overland distance of travel. RESULTS: Two hundred and forty-three patients travelled by air; mean flight time was 74 min. In total, 5498 patients travelled a mean 25.3 miles over land to the hospital. No differences in baseline demographics or ASA score were observed. Four patients developed a VTE in the flight group, with 32 patients suffering a VTE in the control group. There was a significant difference in the VTE rate between the flight and control groups (p < 0.05); the relative risk of developing a VTE in the flight group was 2.85. CONCLUSIONS: In our cohort, perioperative short haul air travel is associated with an increased risk of VTE at 90 days following LLA. Orthopaedic surgeons must ensure that their patients are cognizant of the risks associated with perioperative air travel and take measures to minimise these risks.

Using Population Mobility Patterns to Adapt COVID-19 Response Strategies in 3 East Africa Countries.

The COVID-19 pandemic spread between neighboring countries through land, water, and air travel. Since May 2020, ministries of health for the Democratic Republic of the Congo, Tanzania, and Uganda have sought to clarify population movement patterns to improve their disease surveillance and pandemic response efforts. Ministry of Health-led teams completed focus group discussions with participatory mapping using country-adapted Population Connectivity Across Borders toolkits. They analyzed the qualitative and spatial data to prioritize locations for enhanced COVID-19 surveillance, community outreach, and cross-border collaboration. Each country employed varying toolkit strategies, but all countries applied the results to adapt their national and binational communicable disease response strategies during the pandemic, although the Democratic Republic of the Congo used only the raw data rather than generating datasets and digitized products. This 3-country comparison highlights how governments create preparedness and response strategies adapted to their unique sociocultural and cross-border dynamics to strengthen global health security.

Assessing air travel safety in neuromuscular disease: standard versus prolonged hypoxic challenge tests.

PURPOSE: The hypoxic challenge test (HCT) is used to evaluate safety for air travel in individuals with respiratory disease by breathing in 15% oxygen for 20 min. Our aim was to determine if a prolonged HCT, lasting 120 min, identified more individuals with neuromuscular disease at potential risk than the standard HCT lasting 20 min. METHODS: This was a cross-sectional study. All of the clinical testing took place at SickKids, Toronto, Canada. Patients were included in the study if they had a diagnosis of NMD, greater than 6 years of age, resting oxygen saturation ≥ 94%, and partial pressure of carbon dioxide (pCO2) ≤ 45 mmHg. Notable exclusion criteria were left ventricular ejection fraction < 30%, presence of a tracheostomy, and use of non-invasive ventilation for more than 12 h daily. Participants underwent a standard HCT as well as the prolonged HCT on the same day. RESULTS: Twenty-three patients consented to the study. One patient was withdrawn because he was unable to follow the study procedures. The 22 study participants had a mean age of 14.9 years (standard deviation (SD) of 5 years). Seventeen (77%) participants were male. Two participants were withdrawn on the day of testing due to hypercapnia. Twenty participants completed the standard and prolonged HCTs. None of the participants had a positive standard or prolonged HCT. CONCLUSION: Our results suggest that performing a standard or prolonged HCT may, in fact, not be of clinical utility in individuals with less severe NMD.