GlobalHealth Threats

A study, published in Emerging Infectious Diseases, measured asymptomatic transmission of SARS-CoV-2 on an evacuation flight in March 2020. Out of the 310 passengers who boarded a flight from Milan, Italy, to South Korea, 11 passengers with symptoms were removed. For the remainder, N95 respirators were provided and passengers were kept 2 metres apart during pre-boarding. Other than at mealtimes, most passengers wore the N95 respirators throughout the flight. On arrival, all passengers were examined and quarantined for 2 weeks at a government quarantine facility in South Korea. They were tested for SARS-CoV-2 on quarantine day 1 and 14. Among the 299 passengers, 6 passengers (who did not have symptoms) tested positive for the virus on day 1 and were transferred immediately to hospital. Asymptomatic was defined as those with no symptoms when they tested positive and did not develop symptoms within 14 days after testing.

One passenger tested positive on day 14 of quarantine. This individual had previously quarantined in Italy for 3 weeks before boarding, and had worn an N95 respirator whilst travelling, except when using a shared toilet. The toilet was also used by one of the asymptomatic patients identified during quarantine. This indicates transmission was most likely in-flight via indirect contact with an asymptomatic person.

The researchers concluded ‘Considering the difficulty of airborne infection transmission in-flight because of high-efficiency particulate-arresting filters used in aircraft ventilation systems, contact with contaminated surfaces or infected persons when boarding, moving, or disembarking from the aircraft may play a critical role in in-flight transmission of infectious diseases”. They recommend “First, masks should be worn during the flight. Second, because contact with contaminated surfaces increases the risk for transmission of SARS-CoV-2 among passengers, hand hygiene is necessary to prevent infections. Third, physical distance should be maintained before boarding and after disembarking from the aircraft.”