A recent study on the medRxiv preprint server examines how SARS-CoV-2, the virus causing COVID-19, spreads among passengers and crew on airplanes. Researchers reviewed contact tracing data, analyzing factors like seating proximity and mask use that affect infection rates. This study offers essential insights for managing future respiratory pandemics in air travel.
Background
SARS-CoV-2 transmission on planes can occur through droplets, aerosols, and contaminated surfaces. Boarding and deplaning increase this risk, prompting airlines to adopt safety measures during the COVID-19 pandemic. These measures included mandatory masks, limited in-flight services, physical distancing, and high-efficiency particulate air (HEPA) filters. Earlier research on diseases like SARS-CoV-1 and influenza provided some insight, but new data was needed to fully understand SARS-CoV-2’s spread on airplanes.
Study Overview
The study reviewed contact-tracing reports, transmission factors, and secondary attack rates—the likelihood of infection within a group—during flights. Researchers assessed the quality of each study using a nine-point tool, ensuring a transparent evaluation of the evidence. They believe the findings will help shape public health policies and pandemic readiness for air travel.
Using a predefined set of criteria, the study included research published from 2020 to late 2023. It focused on passenger and crew transmission within aircraft and expanded to pre-boarding, post-boarding, and airport transit times. This broad approach aimed to capture all phases of flight-associated transmission. Researchers collected data on flight type, transmission rates, index cases, non-pharmaceutical interventions, and the SARS-CoV-2 variant involved.
Findings
The study found that in-flight transmission of SARS-CoV-2 was sporadic, with secondary attack rates ranging from 0% to 10%, similar to previous findings (0% to 16%). Mask-wearing significantly lowered transmission, with crew and passengers who wore masks experiencing fewer infections. However, brief mask removal during meals sharply increased infection risk by as much as 59%.
Proximity to an infected passenger was also a strong risk factor. Passengers seated within two rows of an infected individual had higher infection rates than those seated further away. These findings align with past studies on similar viruses, showing that close contact elevates infection risk.
While the study did not quantify the impact of HEPA filters, results suggested these filters reduce airborne transmission and limit spread to nearby contacts. Both short and long flights saw infections, indicating that flight duration alone does not clearly affect transmission risk.
Most reported cases involved the Kappa variant, which was widespread at the time. Some infections occurred despite mask use and negative PCR tests, showing that no single measure fully prevents transmission.
Conclusion
The study highlights that SARS-CoV-2 transmission on airplanes is sporadic, with mask use and proximity to infected individuals being key factors in infection risk. The researchers stress the need for consistent reporting in future studies to better guide public health policies. This analysis provides valuable insights that could help create effective guidelines for air travel in future pandemics.
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