Probability and estimated risk of SARS-CoV-2 transmission in the air travel system

Contraction of Respiratory Viral Infection During air Travel: An Under-Recognized Health Risk for Athletes

Air travel has an important role in the spread of viral acute respiratory infections (ARIs). Aircraft offer an ideal setting for the transmission of ARI because of a closed environment, crowded conditions, and close-contact setting. Numerous studies have shown that influenza and COVID-19 spread readily in an aircraft with one virus-positive symptomatic or asymptomatic index case. The numbers of secondary cases differ markedly in different studies most probably because of the wide variation of the infectiousness of the infector as well as the susceptibility of the infectees. The primary risk factor is sitting within two rows of an infectious passenger. Elite athletes travel frequently and are thus prone to contracting an ARI during travel. It is anecdotally known in the sport and exercise medicine community that athletes often contract ARI during air travel. The degree to which athletes are infected in an aircraft by respiratory viruses is unclear. Two recent studies suggest that 8% of Team Finland members traveling to major winter sports events contracted the common cold most probably during air travel. Further prospective clinical studies with viral diagnostics are needed to understand the transmission dynamics and to develop effective and socially acceptable preventive measures during air travel.

Crossing borders to change lives: Surgical mission amidst the COVID-19 pandemic

INTRODUCTION

During the COVID pandemic, elective global surgical missions were temporarily halted for the safety of patients and travelling healthcare providers. We discuss our experience during our first surgical mission amidst the pandemic. We report a safe and successful treatment of the patients, detailing our precautionary steps and outcomes.

METHODS

Retrospective manual chart review and data collection of patients' charts was conducted after IRB approval. We entail our experience and safety steps followed during screening, operating and postoperative care to minimize exposure and improve outcomes during a surgical mission in an outpatient setting during the pandemic. The surgical mission was from February 8 to February 12, 2022.

RESULTS

A total of 60 patients who were screened. 33 patients underwent surgical intervention. One patient required postoperative hospitalization for a biliary duct leak. No patient or healthcare provider tested positive for COVID at the end of the mission. The average age of patients was 46.9 years. The average operative time was 116 min, and all patients had local nerve blocks. It included 45 health work providers.

CONCLUSIONS

It is safe to perform outpatient international surgery during the pandemic while following pre-selected precautions.

Does 2x2 airplane passenger contact tracing for infectious respiratory pathogens work? A systematic review of the evidence

We critically appraised the literature regarding in-flight transmission of a range of respiratory infections to provide an evidence base for public health policies for contact tracing passengers, given the limited pathogen-specific data for SARS-CoV-2 currently available. Using PubMed, Web of Science, and other databases including preprints, we systematically reviewed evidence of in-flight transmission of infectious respiratory illnesses. A meta-analysis was conducted where total numbers of persons on board a specific flight was known, to calculate a pooled Attack Rate (AR) for a range of pathogens. The quality of the evidence provided was assessed using a bias assessment tool developed for in-flight transmission investigations of influenza which was modelled on the PRISMA statement and the Newcastle-Ottawa scale. We identified 103 publications detailing 165 flight investigations. Overall, 43.7% (72/165) of investigations provided evidence for in-flight transmission. H1N1 influenza A virus had the highest reported pooled attack rate per 100 persons (AR = 1.17), followed by SARS-CoV-2 (AR = 0.54) and SARS-CoV (AR = 0.32), Mycobacterium tuberculosis (TB, AR = 0.25), and measles virus (AR = 0.09). There was high heterogeneity in estimates between studies, except for TB. Of the 72 investigations that provided evidence for in-flight transmission, 27 investigations were assessed as having a high level of evidence, 23 as medium, and 22 as low. One third of the investigations that reported on proximity of cases showed transmission occurring beyond the 2x2 seating area. We suggest that for emerging pathogens, in the absence of pathogen-specific evidence, the 2x2 system should not be used for contact tracing. Instead, alternate contact tracing protocols and close contact definitions for enclosed areas, such as the same cabin on an aircraft or other forms of transport, should be considered as part of a whole of journey approach.

Suitability of aircraft wastewater for pathogen detection and public health surveillance

International air travel is now widely recognised as one of the primary mechanisms responsible for the transnational movement and global spread of SARS-CoV-2. Monitoring the viral load and novel lineages within human-derived wastewater collected from aircraft and at air transport hubs has been proposed as an effective way to monitor the importation frequency of viral pathogens. The success of this approach, however, is highly dependent on the bathroom and defecation habits of air passengers during their journey. In this study of UK adults (n = 2103), we quantified the likelihood of defecation prior to departure, on the aircraft and upon arrival on both short- and long-haul flights. The results were then used to assess the likelihood of capturing the signal from infected individuals at UK travel hubs. To obtain a representative cross-section of the population, the survey was stratified by geographical region, gender, age, parenting status, and social class. We found that an individual's likelihood to defecate on short-haul flights (< 6 h in duration) was low (< 13 % of the total), but was higher on long-haul flights (< 36 %; > 6 h in duration). This behaviour pattern was higher among males and younger age groups. The maximum likelihood of defecation was prior to departure (< 39 %). Based on known SARS-CoV-2 faecal shedding rates (30-60 %) and an equal probability of infected individuals being on short- (71 % of inbound flights) and long-haul flights (29 %), we estimate that aircraft wastewater is likely to capture ca. 8-14 % of SARS-CoV-2 cases entering the UK. Monte Carlo simulations predicted that SARS-CoV-2 would be present in wastewater on 14 % of short-haul flights and 62 % of long-haul flights under current pandemic conditions. We conclude that aircraft wastewater alone is insufficient to effectively monitor all the transboundary entries of faecal-borne pathogens but can form part of a wider strategy for public heath surveillance at national borders.

Evaluating vacant middle seats and masks as Coronavirus exposure reduction strategies in aircraft cabins using particle tracer experiments and computational fluid dynamics simulations

Aircraft cabins have high-performance ventilation systems, yet typically hold many persons in close proximity for long durations. The current study estimated airborne virus exposure and infection reductions when middle seats are vacant compared to full occupancy and when passengers wear surgical masks in aircraft. Tracer particle data reported by U.S. Transportation Command (TRANSCOM) and CFD simulations reported by Boeing were used along with NIOSH data, to build nonlinear regression models with particle exposure and distance from particle source as variables. These models that estimate exposure at given distances from the viral source were applied to evaluate exposure reductions from vacant middle seats. Reductions averaged 54% for the seat row where an infectious passenger is located and 36% for a 24-row cabin containing one infectious passenger, with middle seats vacant. Analysis of the TRANSCOM data showed that universal masking (surgical masks) reduced exposures by 62% and showed masking and physical distancing provide further reductions when practiced together. For a notional scenario involving 10 infectious passengers, compared with no intervention, masking, distancing, and both would prevent 6.2, 3.8, and 7.6 secondary infections, respectively, using the Wells-Riley equation. These results suggest distancing alone, masking alone, and these practiced together reduce SARS CoV-2 exposure risk in increasing order of effectiveness, when an infectious passenger is present.

Travel-associated SARS-CoV-2 transmission documented with whole genome sequencing following a long-haul international flight

BACKGROUND

Multiple instances of flight-associated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) transmission during long-haul flights have been reported during the COVID-19 pandemic. However, comprehensive investigations of passenger risk behaviours, before, during and after the flight, are scarce.

METHODS

To investigate suspected SARS-CoV-2 transmission during a flight from United Arab Emirates to Australia in July 2020, systematic, repeated polymerase chain reaction (PCR) testing of passengers in hotel quarantine was linked to whole genome sequencing. Epidemiological analyses of in-depth interviews covering behaviours during the flight and activities pre- and post-boarding were used to identify risk factors for infection.

RESULTS

Seventeen of the 95 passengers from four different travel origins had PCR-confirmed infection yielding indistinguishable genomic sequences. Two of the 17 passengers were symptomatic within 2 days of the flight, and classified as co-primary cases. Seven secondary cases were seated within two rows of the co-primary cases, but five economy passengers seated further away and three business class passengers were also infected (attack rate = 16% [15/93]). In multivariable analysis, being seated within two rows of a primary case [odds ratio (OR) 7.16; 95% confidence interval (CI) 1.66-30.85] and spending more than an hour in the arrival airport (OR 4.96; 95% CI 1.04-23.60) were independent predictors of secondary infection, suggesting travel-associated SARS-CoV-2 transmission likely occurred both during and after the flight. Self-reported increased hand hygiene, frequent aisle walking and using the bathroom on the plane did not independently affect the risk of SARS-CoV-2 acquisition.

CONCLUSIONS

This investigation identified substantial in-flight transmission among passengers seated both within and beyond two rows of the primary cases. Infection of passengers in separate cabin classes also suggests transmission occurred outside the cabin environment, likely at the arrival airport. Recognizing that transmission may occur pre- and post-boarding may inform contact tracing advice and improve efforts to prevent future travel-associated outbreaks.

The COVID-19 pandemic: Virus transmission and risk assessment

The coronaviruses are the largest known RNA viruses of which SASR-CoV-2 has been spreading continuously due to its repeated mutation triggered by several environmental factors. Multiple human interventions and lessons learned from the SARS 2002 outbreak helped reduce its spread considerably, and thus, the virus was contained but the emerging mutations burdened the medical facility leading to many deaths in the world. As per the world health organization (WHO) droplet mode transmission is the most common mode of SASR-CoV-2 transmission to which environmental factors including temperature and humidity play a major role. This article highlights the responsibility of environmental causes that would affect the distribution and fate of the virus. Recent development in the risk assessment models is also covered in this article.

The emission and dynamics of droplets from human expiratory activities and COVID-19 transmission in public transport system: A review

The public transport system, containing a large number of passengers in enclosed and confined spaces, provides suitable conditions for the spread of respiratory diseases. Understanding how diseases are transmitted in public transport environment is of vital importance to public health. However, this is a highly multidisciplinary matter and the related physical processes including the emissions of respiratory droplets, the droplet dynamics and transport pathways, and subsequently, the infection risk in public transport, are poorly understood. To better grasp the complex processes involved, a synthesis of current knowledge is required. Therefore, we conducted a review on the behaviors of respiratory droplets in public transport system, covering a wide scope from the emission profiles of expiratory droplets, the droplet dynamics and transport, to the transmission of COVID-19 in public transport. The literature was searched using related keywords in Web of Science and PubMed and screened for suitability. The droplet size is a key parameter in determining the deposition and evaporation, which together with the exhaled air velocity largely determines the horizontal travel distance. The potential transmission route and transmission rate in public transport as well as the factors influencing the virus-laden droplet behaviors and virus viability (such as ventilation system, wearing personal protective equipment, air temperature and relative humidity) were also discussed. The review also suggests that future studies should address the uncertainties in droplet emission profiles associated with the measurement techniques, and preferably build a database based on a unified testing protocol. Further investigations based on field measurements and modeling studies into the influence of different ventilation systems on the transmission rate in public transport are also needed, which would provide scientific basis for controlling the transmission of diseases.

Recent progress on studies of airborne infectious disease transmission, air quality, and thermal comfort in the airliner cabin air environment

Airborne transmission of infectious diseases through air travel has become a major concern, especially during the COVID-19 pandemic. The flying public and crew members have long demanded better air quality and thermal comfort in commercial airliner cabins. This paper reviewed studies related to the airliner cabin air environment that have been published in scientific journals since 2000, to understand the state-of-the-art in cabin air environment design and the efforts made to improve this environment. In this critical review, this paper discusses the challenges and opportunities in studying the cabin air environment. The literature review concluded that current environmental control systems for airliner cabins have done little to stop the airborne transmission of infectious diseases. There were no reports of significant air quality problems in cabins, although passengers and crew members have complained of some health-related issues. The air temperature in cabins needs to be better controlled, and therefore, better thermal comfort models for airliners should be developed. Low humidity is a major complaint from passengers and crew members. Gaspers are used by passengers to adjust thermal comfort, but they do not improve air quality. Various personalized and displacement ventilation systems have been developed to improve air quality and thermal comfort. Air cleaning technologies need to be further developed. Good tools are available for designing a better cabin air environment.

Risk of COVID-19 Transmission Aboard Aircraft: An Epidemiological Analysis Based on the National Health Information Platform

Objectives

This study aims to investigate the risk of COVID-19 transmission on aircraft.

Methods

We obtained data on all international flights to Lanzhou, China, from June 1, 2020, to August 1, 2020, through the Gansu Province National Health Information Platform and the official website of the Gansu Provincial Center for Disease Control and Prevention. We then performed the statistical analysis.

Results

Three international flights arrived in Lanzhou. The flights had a total of 700 passengers, of whom 405 (57.9%) were male, and 80 (11.4%) were children under the age of 14 years. Twenty-seven (3.9%) passengers were confirmed to have COVID-19. Confirmed patients were primarily male (17, 65.4%) with a median age of 27.0 years. Most confirmed cases were seated in the middle rows of economy class or near public facility areas such as restrooms and galleys. The prevalence of COVID-19 did not differ between passengers sitting in the window, aisle, or middle seats. However, compared with passengers sitting in the same row up to 2 rows behind a confirmed case, passengers seated in the 2 rows in front of a confirmed case were at a slightly higher risk of being infected.

Conclusions

COVID-19 may be transmitted during a passenger flight, although there is still no direct evidence.

Quarantine and testing strategies to ameliorate transmission due to travel during the COVID-19 pandemic: a modelling study

BACKGROUND

Numerous countries have imposed strict travel restrictions during the COVID-19 pandemic, contributing to a large socioeconomic burden. The long quarantines that have been applied to contacts of cases may be excessive for travel policy.

METHODS

We developed an approach to evaluate imminent countrywide COVID-19 infections after 0-14-day quarantine and testing. We identified the minimum travel quarantine duration such that the infection rate within the destination country did not increase compared to a travel ban, defining this minimum quarantine as "sufficient."

FINDINGS

We present a generalised analytical framework and a specific case study of the epidemic situation on November 21, 2021, for application to 26 European countries. For most origin-destination country pairs, a three-day or shorter quarantine with RT-PCR or antigen testing on exit suffices. Adaptation to the European Union traffic-light risk stratification provided a simplified policy tool. Our analytical approach provides guidance for travel policy during all phases of pandemic diseases.

INTERPRETATION

For nearly half of origin-destination country pairs analysed, travel can be permitted in the absence of quarantine and testing. For the majority of pairs requiring controls, a short quarantine with testing could be as effective as a complete travel ban. The estimated travel quarantine durations are substantially shorter than those specified for traced contacts.

FUNDING

EasyJet (JPT and APG), the Elihu endowment (JPT), the Burnett and Stender families' endowment (APG), the Notsew Orm Sands Foundation (JPT and APG), the National Institutes of Health (MCF), Canadian Institutes of Health Research (SMM) and Natural Sciences and Engineering Research Council of Canada EIDM-MfPH (SMM).

Quarantine and testing strategies to ameliorate transmission due to travel during the COVID-19 pandemic: a modelling study

BACKGROUND

Numerous countries imposed strict travel restrictions, contributing to the large socioeconomic burden during the COVID-19 pandemic. The long quarantines that apply to contacts of cases may be excessive for travel policy.

METHODS

We developed an approach to evaluate imminent countrywide COVID-19 infections after 0-14-day quarantine and testing. We identified the minimum travel quarantine duration such that the infection rate within the destination country did not increase compared to a travel ban, defining this minimum quarantine as "sufficient."

FINDINGS

We present a generalised analytical framework and a specific case study of the epidemic situation on November 21, 2021, for application to 26 European countries. For most origin-destination country pairs, a three-day or shorter quarantine with RT-PCR or antigen testing on exit suffices. Adaptation to the European Union traffic-light risk stratification provided a simplified policy tool. Our analytical approach provides guidance for travel policy during all phases of pandemic diseases.

INTERPRETATION

For nearly half of origin-destination country pairs analysed, travel can be permitted in the absence of quarantine and testing. For the majority of pairs requiring controls, a short quarantine with testing could be as effective as a complete travel ban. The estimated travel quarantine durations are substantially shorter than those specified for traced contacts.

FUNDING

EasyJet (JPT and APG), the Elihu endowment (JPT), the Burnett and Stender families' endowment (APG), the Notsew Orm Sands Foundation (JPT and APG), the National Institutes of Health (MCF), Canadian Institutes of Health Research (SMM) and Natural Sciences and Engineering Research Council of Canada EIDM-MfPH (SMM).

Ocular manifestations in COVID-19 patients: A systematic review and meta-analysis

Introduction

With the accumulating evidence of ocular manifestations of the 2019 novel coronavirus disease (COVID-19), the study aimed to systematically summarize the ocular manifestations in COVID-19 patients.

Methods

The PubMed, EMBASE, Web of Science databases were searched through June 2021. Studies that provided clinical characteristics and outcomes and reported on the ocular manifestations or conjunctival swab RT-PCR tests among COVID-19 patients were included.

Results

A total of 30 studies involving 5,717 patients were identified. Ocular manifestations including conjunctival hyperemia (7.6%, 95% confidence interval [CI] 1.8–8.9%), conjunctival discharge (4.8%, 95% CI 1.8–8.9%), epiphora (6.9%, 95% CI 2.8–12.8%), and foreign body sensation (6.9%, 95% CI 2.4–13.0%) were observed. The positive rate of conjunctival swab tests was 3.9% (95% CI 0.2–6.4%). Severe cases of COVID-19 were associated with an increased risk of developing ocular complications (odds ratio [OR] = 2.77, 95% CI 1.75–4.40).

Conclusions

Despite their relatively low incidence rate in COVID-19 patients, ocular manifestations may be non-specific and present as the initial symptoms of infection. The presence of SARS-CoV-2 in the conjunctival swabs implicates the eye as a potential source of infection. Early diagnosis and proper eye protection would help prevent viral transmission.

COVID-19 transmission and the safety of air travel during the pandemic: a scoping review

PURPOSE OF REVIEW

To examine the literature assessing safety of air travel relating to coronavirus disease 2019 (COVID-19) transmission from January 2020 to May 2021. The COVID-19 pandemic has had an unprecedented impact on air travel and global mobility, and various efforts are being implemented to determine a safe way forward. As the pandemic evolves, so do the challenges that force various stakeholders, including the aviation industry, health authorities, and governments, to reassess and adapt their practices to ensure the safety of travellers.

RECENT FINDINGS

The literature was reviewed for multiple aspects of air travel safety during the COVID-19 pandemic. Recurring themes that surfaced included the pivotal role of commercial air travel in the geographic spread of COVID-19, the efficacy of travel restrictions and quarantines, inflight transmission risk and the role of preventive measures, the utility of pre and post flight testing, the development of effective vaccines and subsequent challenges of vaccine passports, and the ongoing threat of novel highly transmissible variants.

SUMMARY

Much uncertainty lies ahead within the domains of these findings, and ongoing research, discourse and review will be necessary to navigate and determine the future direction and safety of air travel. Recovery will be slow, necessitating innovative, multipronged and collaborative solutions.