Investigation of a COVID-19 Cluster Suspected In-flight Transmission, December 2020

Abstract

On 1 Dec 2020, the Thai Department of Disease Control was notified of five COVID-19 infections among passengers on a flight from Switzerland to Thailand. The objectives of this investigation were to confirm the outbreak, describe epidemiological characteristics, and identify the source of infection. We performed a descriptive study and contact tracing among the flight’s passengers. We interviewed the cases and reviewed their medical records, as well as an environmental survey of the state quarantine facility. Whole genome sequencing to determine the percentage alignment identity for RT-PCR-positive cases was conducted. Thirteen infected passengers out of 107 people on the flight (12.1%) were identified. The suspected index case was a symptomatic passenger, non-mask-wearing passenger. Five of the 13 confirmed cases shared a similar genomic pattern (98–100% alignment identity), and four cases sat within one row either in front of or behind the suspected index case. The genomes of the cases were more similar to each other than those uploaded to the GISAID database from Switzerland. The symptomatic COVID-19 passenger without mask wearing was suspected to be the source. Mask wearing should be mandated on flight to prevent spreading of respiratory infectious diseases.

Keywords: COVID-19, in-flight transmission, on plane transmission, airplane transmission, coronavirus, respiratory virus