Updated:01/08/2021 17: 37h
Is it safe to fly in times of covid-19? Air filtration systems in airplanes are assumed to reduce the risk of infection among passengers, even when one or more infected persons are on the flight. Airlines have updated and adjusted their requirements for travelers, with mixed results: some work to maintain social distance, but others are less attentive.
Sometimes the use of masks depends on passenger compliance and is not predictable; nor, increasingly, the flight capacity, which can oscillate between 20 percent, but there are flights that go almost complete.
That makes the millions of airline passengers experience first-hand the uncertainties that come with flying during a pandemic.
Due to multiple variables, infectious disease specialists have had a difficult time determining the risks of flying. But a study published this week in « Emerging Infectious Diseases»Provides some light.
The study details the events that occurred on an 18-hour flight, from Dubai is Auckland (New Zealand), last September, which was the origin of an outbreak that probably occurred during the trip.
The researchers, using seat plans and genetic analysis, determined that one passenger started a chain of infection that spread to four others during the journey.
The analysis, led by researchers from the New Zealand Ministry of Health, found that seven of the 86 passengers on board tested positive during their quarantine and that at least four were infected on the flight. The plane, a Boeing 77, with a capacity of almost 400 passengers, had a 25% occupancy.
These seven passengers came from five countries. Two acknowledged that they did not wear masks and that the airline did not require them to wear them in the lobby before boarding. It also did not require pre-flight testing, although five of the seven passengers who later tested positive had undergone a test and received a negative result in the days leading up to boarding.
The versions of the coronavirus carried by all seven were practically genetically identical, suggesting that one of them started the outbreak. That person, whom the report calls Passenger A, had in fact tested negative four or five days prior to boarding.
Evidence of transmission on that flight is supported by epidemiological data, symptom onset dates, and genomic data from this group of travelers who tested positive for SARS-CoV-2.
Of the 7 passengers, two (A and B) were probably the index cases – and were infected before the flight, four (C, D, E, and F) were probably infected during the flight, and the remaining passenger (G) was infected while in quarantine. “The 7 passengers were located in aisle seats 2 rows away from where the alleged index cases were sitting,” they write in their article.
Researchers from the New Zealand Ministry of Health claim that «These data present a likely scenario of more than 4 SARS-CoV-2 transmission events during a long-haul flight from Dubai to Auckland. And this transmission occurred despite the use of masks and gloves».
These conclusions are supported by genome sequencing, an onboard seating chart and disease onset dates, they write.
However, they acknowledge that this data does not totally exclude an alternative exposure event, such as virus transmission at Dubai airport prior to boarding (for example, during check-in or in boarding queues). However, “the proximity of the relevant passengers on board suggests that in-flight transmission is plausible,” they conclude.
And, because similar reports of SARS-CoV-2 transmission during flight have been released recently, experts note that the information demonstrates the potential for SARS-CoV-2 to spread on long-haul flights.
In addition, the report warns of another very relevant event. “The fact that 3 passengers tested positive for COVID-19 on the third day of their 14-day quarantine period indicates some of the complexities of determining the value of pre-departure tests, including type and timing of said tests ”.
The results are very relevant because, unlike other previously reported works, when few travelers wore masks, the planes were operating almost at their full capacity and the value of preventive measures had not been assumed, the new report, of a flight in largely empty, detailing what can happen even when airlines and passengers are aware and more cautious of the risks.
The findings are not definitive, cautioned the authors, led by Dr. Tara Swadi. But the results «underscore the value of considering all international passengers arriving in New Zealand as potentially infected, even if pre-departure testing was done, social distancing was maintained and personal protective equipment was used during the flight», They conclude.