|
 Dr David Freedman, a U.S. infectious diseases specialist, said he
declined to take part in a recent presentation by global airline
body IATA with planemakers Airbus, Boeing and Embraer that cited his
work.
While he welcomed some industry findings as "encouraging", Freedman
said a key assertion about the improbability of catching COVID-19 on
planes was based on "bad math".
Airlines and planemakers are anxious to restart international
travel, even as a second wave of infections and restrictions take
hold in many countries.
The Oct. 8 media presentation listed in-flight infections reported
in scientific studies or by IATA airlines - and compared the tally
with total passenger journeys this year.
"With only 44 identified potential cases of flight-related
transmission among 1.2 billion travellers, that's one case for every
27 million," IATA medical adviser Dr David Powell said in a news
release, echoed in comments during the event.
IATA said its findings "align with the low numbers reported in a
recently published peer-reviewed study by Freedman and
Wilder-Smith".
But Freedman, who co-authored the paper in the Journal of Travel
Medicine with Dr Annelies Wilder-Smith of the London School of
Hygiene and Tropical Medicine, said he took issue with IATA's risk
calculation because the reported count bore no direct relation to
the unknown real number of infections.
"They wanted me at that press conference to present the stuff, but
honestly I objected to the title they had put on it," the University
of Alabama academic told Reuters.
"It was bad math. 1.2 billion passengers during 2020 is not a fair
denominator because hardly anybody was tested. How do you know how
many people really got infected?" he said. "The absence of evidence
is not evidence of absence."
IATA believes its calculation remains a "relevant and credible" sign
of low risk, a spokesman said in response to requests for comment
from the industry body and its top medic Powell.
"We've not claimed it's a definitive and absolute number."
Wilder-Smith could not be immediately reached for comment.
CLOSING RANKS
While the pandemic has seen some airlines leave middle seats empty
to reassure customers, the industry has opposed making such measures
mandatory.
Plane cabins are considered lower-risk than many indoor spaces
because of their powerful ventilation and their layout, with
forward-facing passengers separated by seat rows. Ceiling-to-floor
airflows sweep pathogens into high-grade filters.
That understanding is supported by simulations and tests run by the
aircraft makers as well as a U.S. Defense Department study released
on Thursday.
The joint presentation with all three manufacturers signalled a rare
closing of ranks among industrial archrivals, behind a message
designed to reassure.
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Sitting beside an infected economy passenger is comparable to seven-foot
distancing in an office, Boeing tests concluded, posing an acceptably low risk
with masks. Standard health advice often recommends a six-foot separation.
Airbus showed similar findings, while Embraer tested droplet dispersal from a
cough. Some 0.13% by mass ended up in an adjacent passenger's facial area,
falling to 0.02% with masks.
Dr Henry Wu, associate professor at Atlanta's Emory School of Medicine, said the
findings were inconclusive on their own because the minimum infective dose
remains unknown, and risks increase in step with exposure time.
"It's simply additive," said Wu, who would prefer middle seats to be left empty.
"A 10-hour flight will be 10 times riskier than a one-hour flight."
Nonetheless, a commercial jet cabin is "probably one of the safer public
settings you can be in," he added. "Sitting at a crowded bar for a few hours is
going to be much riskier."
'SUPERSPREADER EVENTS'
Scientists are poring over dozens of on-board infection cases, as well as
flights with contagious passengers but no known transmission.
In March, 11 infectious passengers on a five-hour Sydney-Perth flight passed the
virus to 11 others, according to a paper in the Emerging Infectious Diseases
journal.
Among those infected, two were seated three rows away from a contagious
passenger and one was six rows away, suggesting that typical two-row
contact-tracing might have missed them.
One sufferer on a 10-hour London-Hanoi flight the same month infected 16 others
including 12 in her business-class cabin, according to a study by Vietnamese and
Australian academics.
"Long flights ... can provide conditions for superspreader events," the study
said, adding that its findings "challenge" the airlines' assertion that on-board
distancing is unnecessary.
IATA points out that many of the flights examined by scientists in published
studies occurred before mask-wearing became widespread and reduced infection
risks.
Its presentation conceded that the 1-in-27 million statistic "may be an
underestimate", while maintaining that in-flight infections remained less likely
than a lightning strike, even if only 10% of actual cases had made the count.
"That's misleading," Emory's Wu said. "Thinking about how hard it is to identify
them, I wouldn't be surprised if it's far less than 1%. The only thing I'm sure
of is that it's a fantastic underestimate."
(Reporting by Laurence Frost; Editing by Pravin Char)
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