'Bad math': Airlines' COVID safety analysis challenged by expert

By Laurence Frost

 

FILE PHOTO: Passengers wearing protective face masks sit on a plane at Sharm el-Sheikh International Airport, following the outbreak of the coronavirus disease (COVID-19), in Sharm el-Sheikh, Egypt, June 20, 2020. REUTERS/Mohamed Abd El Ghany

 

PARIS (Reuters) - A campaign by coronavirus-stricken aviation giants to persuade the world it's safe to fly has been questioned by one of the scientists whose research it draws upon.

 

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.

 

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."

 

-- © Copyright Reuters 2020-10-19

 

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I'll pass  on flying for now..

4 hours ago, from the home of CC said:

I'll pass  on flying for now..

#metoo

13 hours ago, snoop1130 said:

"With only 44 identified potential cases of flight-related transmission among 1.2 billion travellers, that's one case for every 27 million,"

I would think that Thailand alone has more potential cases of flight-related transmission.

Once the plane is in the air and the ventilation systems are on, especially if they added UV-C lamps at the HEPA filters that circulate the air, the probability of infection would be close to 0. I think each infected person cold only infect one person sitting in front, and side of him, due to the way the air flow works on a modern jet. However... that's not the case in airports, and certainly not on the way to the plane (boarding tunnel or a bus), queue of people in close proximity getting into the plane and to their seats... And same for disembarking. It would be my humble opinion that these are likely cause for most infections and far less sitting in your seat 35k ft above the ground.

 

As for the scientist's claim of bad maths... He's also using bad maths for his research, unless he's tested all 7+ billion people at the same time. And since he hasn't - how can he say how many percent of people are really infected? How many of infected are having severe symptoms or die? Hence good to call it out, but he's doing exactly the same.

Yup I am also not going on a long flight until at least next Winter.  Maybe by then

more research will have been done, and a vaccine will be out and being used by then.

I will still wear a mask ,N95 model on the flight just to be a little more sure.

Geezer

5 hours ago, Stargrazer9889 said:

Yup I am also not going on a long flight until at least next Winter.  Maybe by then

more research will have been done, and a vaccine will be out and being used by then.

I will still wear a mask ,N95 model on the flight just to be a little more sure.

Geezer

COVID is a lot smaller than what even best HEPA filters can stop. N95 mask filters 95% of pm2.5, where COVID is pm0.15.

I'll agree with tomazbodner above. Pre-this year I suffered a common cold or flu (the snotty nose, headaches, coughing etc) about 3-4 times per year, usually within a day of arrival at my destination. (An annual flu jab took that down to 1-2 times a year, but I still get them). I always put this down to the 8 to 12 long haul flights in/out of Thailand I made to get to work. The general crowding in the queues to board flights as well as the packing in of passengers must be a factor. Then an aircraft recycles... I forget. I think it's 50% of it's air. So the 300 odd people are always breathing each others air for 6-18hours at, what 20 air changes per hour? 

 

Then we add in that many of the airlines fly aging aircraft and we all know horror stories on important maintenance, let alone something like the air systems. Those filters will not get cleaned often, if they ever had HEPA filters that is.

 

Nope, flying is still the best way to spread disease. How do they think it spread from Wuhan in the first place?

2 hours ago, tomazbodner said:

COVID is a lot smaller than what even best HEPA filters can stop. N95 mask filters 95% of pm2.5, where COVID is pm0.15.

No!

https://eu.usatoday.com/story/news/factcheck/2020/06/11/fact-check-n-95-filters-not-too-large-stop-covid-19-particles/5343537002/

"The COVID-19 virus itself is indeed smaller than the N95 filter size, but the virus always travels attached to larger particles that are consistently snared by the filter. And even if the particles were smaller than the N95 filter size, the erratic motion of particles that size and the electrostatic attraction generated by the mask means they would be consistently caught as well."

Two observations:

 

1. People who do a lot of flying catch a lot of colds.

 

2. The drive by airlines for ‘smoke free’ flights was driven by economics - Aircraft regulations required ‘smoking permitted’ flights to change the cabin air 20 times per hour v 12 times per hour for ‘non smoking’ flights.  The reduction in required ‘air changes’ permits a reduction in the size and energy requirements of the air handling units.

 

 

On 10/19/2020 at 6:21 AM, from the home of CC said:

I'll pass  on flying for now..

 

It's great that you can make that personal choice without losing your job or missing your family.  Millions of people aren't in that position.

 

4 hours ago, Narratio said:

I'll agree with tomazbodner above. Pre-this year I suffered a common cold or flu (the snotty nose, headaches, coughing etc) about 3-4 times per year, usually within a day of arrival at my destination. (An annual flu jab took that down to 1-2 times a year, but I still get them). I always put this down to the 8 to 12 long haul flights in/out of Thailand I made to get to work. The general crowding in the queues to board flights as well as the packing in of passengers must be a factor. Then an aircraft recycles... I forget. I think it's 50% of it's air. So the 300 odd people are always breathing each others air for 6-18hours at, what 20 air changes per hour? 

 

Then we add in that many of the airlines fly aging aircraft and we all know horror stories on important maintenance, let alone something like the air systems. Those filters will not get cleaned often, if they ever had HEPA filters that is.

 

Nope, flying is still the best way to spread disease. How do they think it spread from Wuhan in the first place?

Very doubtful it was spread from wuhan on the plane.

2 hours ago, Old Nomad said:

No!

https://eu.usatoday.com/story/news/factcheck/2020/06/11/fact-check-n-95-filters-not-too-large-stop-covid-19-particles/5343537002/

"The COVID-19 virus itself is indeed smaller than the N95 filter size, but the virus always travels attached to larger particles that are consistently snared by the filter. And even if the particles were smaller than the N95 filter size, the erratic motion of particles that size and the electrostatic attraction generated by the mask means they would be consistently caught as well."

Thank you for the article. Very insightful. The only issue is that N95 is only effective for 2 hours before it needs to be changed. I would dare to bet people reuse them or use them far longer than 2 hours, which, as article suggests, could discharge the masks and lower their efficiency. Regardless, very good article. Appreciated.

1 hour ago, tomazbodner said:

Thank you for the article. Very insightful. The only issue is that N95 is only effective for 2 hours before it needs to be changed. I would dare to bet people reuse them or use them far longer than 2 hours, which, as article suggests, could discharge the masks and lower their efficiency. Regardless, very good article. Appreciated.

I took a look at how long N95 masks can be used.   I suspect this for those who are using it in a medical-type situation:

 

When practicing extended use of N95 respirators, the maximum recommended extended use period is 8–12 hours. Respirators should not be worn for multiple work shifts and should not be reused after extended use. N95 respirators should be removed (doffed) and discarded before activities such as meals and restroom breaks.

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