Transmission of SARS-CoV-2 during air travel: a descriptive and modelling study

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.

SARS-CoV-2 Cases Reported on International Arriving and Domestic Flights: United States, January 2020-December 2021

Objectives. To describe trends in the number of air travelers categorized as infectious with SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2; the virus that causes COVID-19) in the context of total US COVID-19 vaccinations administered, and overall case counts of SARS-CoV-2 in the United States. Methods. We searched the Quarantine Activity Reporting System (QARS) database for travelers with inbound international or domestic air travel, a positive SARS-CoV-2 lab result, and a surveillance categorization of SARS-CoV-2 infection reported during January 2020 to December 2021. Travelers were categorized as infectious during travel if they had arrival dates from 2 days before to 10 days after symptom onset or a positive viral test. Results. We identified 80 715 persons meeting our inclusion criteria; 67 445 persons (83.6%) had at least 1 symptom reported. Of 67 445 symptomatic passengers, 43 884 (65.1%) reported an initial symptom onset date after their flight arrival date. The number of infectious travelers mirrored the overall number of US SARS-CoV-2 cases. Conclusions. Most travelers in the study were asymptomatic during travel, and therefore unknowingly traveled while infectious. During periods of high community transmission, it is important for travelers to stay up to date with COVID-19 vaccinations and consider wearing a high-quality mask to decrease the risk of transmission. (Am J Public Health. 2023;113(8):904-908. https://doi.org/10.2105/AJPH.2023.307325).

International air travel-related control measures to contain the Covid-19 pandemic: A companion review to a Cochrane rapid review

Background

COVID-19 has proven to be challenging to manage for many reasons, including its high infection rate. One of the potential ways to limit its spread is by limiting international travel. The objective of this systematic review was to identify, critically appraise and summarise evidence on international air travel-related control measures for COVID-19.

Methods

This review is based on the Cochrane review: International travel-related control measures to contain the COVID-19 pandemic and followed the same methods. In brief, we searched for clinical and modelling studies in general health and COVID-19-specific bibliographic databases. The primary outcome categories were (i) cases avoided, (ii) a shift in epidemic development and, (iii) cases detected.

Results

From 6,202 citations identified by the search strategy, we included 22 new studies (modelling = 9, observational = 13) in addition to the 62 studies identified in the Cochrane review. Studies suggest that quarantine or microbial detection or a combination may avoid further cases. Similarly, these interventions may produce a positive shift in epidemic development and case detection may improve. Most studies were evaluated as having a moderate to critical risk of bias. The studies did not change the main conclusions of the Cochrane review nor the quality of the evidence (very low certainty); however, they added to the evidence base for most outcomes.

Conclusions

Weak evidence supports the use of international air travel-related control measures to limit the spread of COVID-19 via air travel. More real-world studies are required to support these conclusions.

Bioaerosol distribution characteristics and potential SARS-CoV-2 infection risk in a multi-compartment dental clinic

Dental clinics have a potential risk of infection, particularly during the COVID-19 pandemic. Multi-compartment dental clinics are widely used in general hospitals and independent clinics. This study utilised computational fluid dynamics to investigate the bioaerosol distribution characteristics in a multi-compartment dental clinic through spatiotemporal distribution, working area time-varying concentrations, and key surface deposition. The infection probability of SARS-CoV-2 for the dental staff and patients was calculated using the Wells-Riley model. In addition, the accuracy of the numerical model was verified by field measurements of aerosol concentrations performed during a clinical ultrasonic scaling procedure. The results showed that bioaerosols were mainly distributed in the compartments where the patients were treated. The average infection probability was 3.8% for dental staff. The average deposition number per unit area of the treatment chair and table are 28729 pcs/m² and 7945 pcs/m², respectively, which creates a possible contact transmission risk. Moreover, there was a certain cross-infection risk in adjacent compartments, and the average infection probability for patients was 0.84%. The bioaerosol concentrations of the working area in each compartment 30 min post-treatment were reduced to 0.07% of those during treatment, and the infection probability was <0.05%. The results will contribute to an in-depth understanding of the infection risk in multi-compartment dental clinics, forming feasible suggestions for management to efficiently support epidemic prevention and control in dental clinics.

The role of precautions: Organising a medical conference during COVID-19 pandemic-Lessons from IADVL MIDDERMACON 2021

Background

The use of virtual platforms for clinical meetings has become the default approach during this pandemic era. Organising an offline conference during a pandemic is a challenge and is possible if the participating crowd is vaccinated and is willing to follow appropriate pandemic protocols.

Objective

To determine the feasibility of conducting a conference among mostly vaccinated delegates using standard precautionary protocols.

Methods

This study was conducted at IADVL MIDDERMACON 2021, held in Mangalore, India, in late October 2021, during the phase of decline of the Delta variant of SARS-CoV-2. The study population included all conference attendees, including support staff. Details were collected about their vaccination status, comorbidities, and mode of travel to the conference venue. An reverse-transcription polymerase chain reaction (RT-PCR) test was done randomly among the attendees for COVID-19 infection. A post-conference assessment and RT-PCR tests were done at the end of 2 weeks to assess the occurrence of infections among study participants.

Results

A total of 1744 people were present at the venue, of which 576 (33.03%) participated in the study. The percentage of fully vaccinated was 88.88% (512/576). The majority had taken the vaccine Covishield (manufactured by AstraZeneca), that is, 85.06% (490/576). Infection post the conference was reported in 0.195% (1/576).

Conclusions

Holding large gatherings like medical conferences pose a challenge during a pandemic. However, to increase the benefits of the conference, it is advisable to hold them offline with vaccinated delegates, follow the advice of the conference organising committee, and practise safe precautionary measures.

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.