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COVID-19: Airlines and medical experts differ over risk of flying

Airlines suffered a COVID-19 setback this week when an expert rejected safety conclusions they drew from his research, writes MedicalBrief. But while numerous studies suggest that SARS-CoV-2 can be transmitted during flights, there appears to be consensus that air travel is likely no more infectious than other forms of public transport.

Further, the risks of infection should reduce. As The Lancet pointed out in a recent editorial, much as travellers adapted to enhanced security following the 9/11 terrorist attacks on the United States: "The COVID-19 pandemic may similarly redefine what is normal for travellers, with a potentially positive outcome of reducing the risk of transmission of many other infections besides COVID-19."

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

A campaign by coronavirus-stricken aviation giants to persuade the world it is safe to fly has been questioned by one of the scientists whose research it draws upon, reports Reuters.

Dr David Freedman, a US infectious diseases specialist, declined to take part in a recent presentation by global airline body IATA – the International Air Transport Association – with plane-makers 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”, writes Laurence Frost in the Reuters article published on 19 October 2020.

Airlines and plane-makers are anxious to restart international travel, even as a second wave of infections and restrictions take hold in many countries.

‘Bad math’

The 8 October 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, the Reuters article continues.

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 March 2020 paper in the Journal of Travel 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 – Calculation ‘relevant and credible’

IATA maintains that its calculation is a “relevant and credible” sign of low risk, a spokesman said in response to requests for comment from the organisation and its top medic Powell. “We’ve not claimed it’s a definitive and absolute number,” Reuters reports.

British Airways directly invoked the 1-in-27 million ratio to press for a lifting of quarantines on Monday. “We know public safety is key for the government, so it should be reassured by IATA’s new figures,” Chief Executive Sean Doyle told a UK aviation conference.

Closing ranks

The Reuters article goes on to say that 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 US Defence Department study released last Thursday.

The joint presentation with all three manufacturers signalled a rare closing of ranks among industrial arch-rivals, 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, Reuters reports.

“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.”

‘Super-spreader events’

Scientists are poring over dozens of on-board infection cases, as well as flights with contagious passengers but no known transmission, according to Reuters.

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 super-spreader 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, reports Reuters.

Its presentation did concede that the 44-case tally “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.”


Flight-Associated Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Corroborated by Whole-Genome Sequencing

Emerging Infectious Diseases. Early release of an article for Volume 26, Number 12 – December 2020


Hollie Speake, Anastasia Phillips, Tracie Chong, Chisha Sikazwe, Avram Levy, Jurissa Lang, Benjamin Scalley, David J. Speers, David W. Smith, Paul Effler, and Suzanne P. McEvoy

Author affiliations

University of Notre Dame in Fremantle, Australia (H Speake); Metropolitan Communicable Disease Control in Perth, Australia (A Phillips, T Chong, B Scalley, SP McEvoy); University of Western Australia (C Sikazwe, A Levy, J Lang, DJ Speers, P Effler); PathWest Laboratory Medicine Western Australia (C Sikazwe, A Levy, DJ Speers, DW Smith, J Lang); Public Health Emergency Operations Centre, Perth (P Effler)


To investigate potential transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during a domestic flight within Australia, we performed epidemiologic analyses with whole-genome sequencing.

Eleven passengers with PCR-confirmed SARS-CoV-2 infection and symptom onset within 48 hours of the flight were considered infectious during travel; 9 had recently disembarked from a cruise ship with a retrospectively identified SARS-CoV-2 outbreak.

The virus strain of those on the cruise and the flight was linked (A2-RP) and had not been previously identified in Australia.

For 11 passengers, none of whom had traveled on the cruise ship, PCR-confirmed SARS-CoV-2 illness developed between 48 hours and 14 days after the flight. Eight cases were considered flight associated with the distinct SARS-CoV-2 A2-RP strain; the remaining 3 cases (1 with A2-RP) were possibly flight associated. All 11 passengers had been in the same cabin with symptomatic persons who had primary, culture-positive, A2-RP cases.

This investigation provides evidence of flight-associated SARS-CoV-2 transmission.


Dispatch: In-Flight Transmission of SARS-CoV-2

Emerging Infectious Diseases. Early release of article for Volume 26, Number 11—November 2020


Edward M Choi, Daniel KW Chu, Peter KC Cheng, Dominic NC Tsang, Malik Peiris, Daniel G Bausch, Leo LM Poon and Deborah Watson-Jones 

Author affiliations

London School of Hygiene & Tropical Medicine (EM Choi, DG Bausch, D Watson-Jones); The University of Hong Kong (DKW Chu, M Peiris, LLM Poon); Department of Health, Government of Hong Kong Special Administrative Region (PKC Cheng, DNC Tsang); Public Health England, London (DG Bausch); National Institute for Medical Research, Tanzania (D Watson-Jones)


Four persons with severe acute respiratory syndrome coronavirus 2 infection had travelled on the same flight from Boston in the United States to Hong Kong, China. Their virus genetic sequences are identical, unique and belong to a clade not previously identified in Hong Kong, which strongly suggests that the virus can be transmitted during air travel.


Transmission of SARS-CoV 2 During Long-Haul Flight

Emerging Infectious Diseases. Early release – Volume 26, Number 11–November 2020


Nguyen Cong Khanh, Pham Quang Thai, Ha-Linh Quach, Ngoc-Anh Hoang Thi, Phung Cong Dinh, Tran Nhu Duong, Le Thi Quynh Mai, Ngu Duy Nghia, Tran Anh Tu, La Ngoc Quang, Tran Dai Quang, Trong-Tai Nguyen, Florian Vogt and Dang Duc Anh

Author affiliations

National Institute of Hygiene and Epidemiology in Hanoi, Vietnam (NC Khanh, PQ Thai, H-L Quach, N-A.H Thi, TN Duong, LTQ Mai, ND Nghia, TA Tu, DD Anh)

Hanoi Medical University (PQ Thai, T-T Nguyen)

Australian National University (H-L Quach, N-A H Thi, F Vogt)

Ministry of Science and Technology, Hanoi (PC Dinh)

Ha Noi University of Public Health, Hanoi (LN Quang)

Ministry of Health in Hanoi, Vietnam (TD Quang)


To assess the role of in-flight transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), we investigated a cluster of cases among passengers on a 10-hour commercial flight. Affected persons were passengers, crew and their close contacts. We traced 217 passengers and crew to their final destinations and interviewed, tested and quarantined them.

Among the 16 persons in whom SARS-CoV-2 infection was detected, 12 (75%) were passengers seated in business class along with the only symptomatic person (attack rate 62%). Seating proximity was strongly associated with increased infection risk (risk ratio 7.3, 95% CI 1.2–46.2). We found no strong evidence supporting alternative transmission scenarios.

In-flight transmission that probably originated from one symptomatic passenger caused a large cluster of cases during a long flight. Guidelines for preventing SARS-CoV-2 infection among air passengers should consider individual passengers’ risk for infection, the number of passengers traveling, and flight duration.


Air travel in the time of COVID-19

The Lancet Infectious Diseases. Published on 1 September 2020. Volume 20, Issue 9


The COVID-19 pandemic is changing the way we think about travelling. Most countries in the world have adopted some measure of lockdown or restriction to movement to reduce transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and ease the burden of admissions in struggling health systems.

These measures have raised questions about the safety of travelling for work and leisure, and current recommendations discourage unnecessary travel. Although the risk of contracting an infectious disease when travelling has always existed, the COVID-19 pandemic has made travellers more aware of this possibility.

However, with the relaxing of lockdown measures in some countries in light of reductions in the number of COVID-19 cases and the holiday season in the northern hemisphere, many people are facing the dilemma of choosing to travel after months of restrictions or to remain at home for fear of being confined in an aeroplane for hours with other people.

Considerations include where it is safe to go, what is the risk of travelling, and what new measures are in place to reduce the risk of COVID-19 for those who decide to travel.

Many countries have introduced border closures to prevent the arrival of infected travellers from countries where there is continuing community transmission of SARS-CoV-2 in order to protect progress made in the control of the pandemic.

Global surveillance of the dynamics of the COVID-19 pandemic is a key element to inform governments around border closures, which is a decision with heavy implications for the economy, especially for countries that rely on tourism as a source of income.

In many cases, instead of full border closure, quarantine is required for any traveller coming from countries where COVID-19 is rife. These measures are dynamically applied depending on changes in the epidemiological situation: an extreme example was quarantine for passengers on a flight from Nice to Oslo because they landed one min after Norway had declared France a high-risk country.

Some countries are instead introducing travel bubbles, also known as coronavirus corridors, which allow the opening of borders with specific countries they deem safe while maintaining more rigid restrictions for the rest of the world.

Individuals must balance risk

Beyond what countries decide, individuals still need to balance benefits and risks of the decision to travel, and with most cruise ships not operating at the moment, the focus for international travellers is on flying.

The very idea of being in close proximity to strangers with an unknown infection status for hours is understandably a concern, although cases of SARS-CoV-2 transmission on aeroplanes have been very few so far.

After the emergence of COVID-19, airlines and airports introduced new rules and measures to minimise the chances of infection with SARS-CoV-2: wearing masks in airports and on aeroplanes, expanded cleaning of public spaces to reduce the presence of the virus on inanimate surfaces, physical distancing (at least 2 m), and hand sanitising.

Some airlines have reduced the number of passengers allowed on a flight to guarantee more distance between travellers or they have cancelled food and drink sales during the flights. Despite concerns about the spread of SARS-CoV-2 through air ventilation, aeroplanes benefit from air-conditioning systems with far more sophisticated and effective filters than those generally found on the ground. The high efficiency particulate air filters used on aeroplanes have been found to remove almost all particles of the typical size of coronavirus.

The future

What does the future hold for travellers? The availability of a COVID-19 vaccine will be instrumental in reinstating confidence in travellers.

However, it is expected that many airlines will cut services such as meals, drinks and free magazines, not so much for economic reasons but as a way to limit so-called touchpoints, which are opportunities for SARS-CoV-2 transmission via close physical proximity between flyers and crew.

Rapid testing for COVID-19 for both crew members and passengers could become a regular feature. Enhanced cleanliness and sanitisation will become the norm. Use of masks or other protective equipment will become more common. Touchless technology will reduce human interaction and facilitate payments and processes linked to travelling.

Following the terrorist attacks of 11 September 2001, travellers adapted to enhanced security controls in airports and strict rules regarding their luggage. The COVID-19 pandemic may similarly redefine what is normal for travellers, with a potentially positive outcome of reducing the risk of transmission of many other infections besides COVID-19.


Risk of COVID-19 During Air Travel

JAMA Network. Published on 1 October 2020


Rui Pombal, Ian Hosegood and David Powell.

Author affiliations

Pombal: Aerospace Medical Association in Virginia, US.

Hosegood: International Airline Medical Association in Virginia, US.

Powell: International Air Transport Association (IATA) in Geneva, Switzerland.

The risk of contracting coronavirus disease 2019 (COVID-19) during air travel is lower than from an office building, classroom, supermarket, or commuter train.

How Is COVID-19 Transmitted?

The virus that causes COVID-19 is emitted when someone talks, coughs, sneezes or sings, mainly in droplets that can be propelled a short distance, and sometimes in smaller aerosol particles that can remain suspended and travel further. Another person can be infected if these particles reach their mouth or nose, directly or via hands. Transmission via surface contact is also important in some cases.

How clean is the air in passenger aircraft?

Air enters the cabin from overhead inlets and flows downwards toward floor-level outlets. Air enters and leaves the cabin at the same seat row or nearby rows. There is relatively little airflow forward and backward between rows, making it less likely to spread respiratory particles between rows.

The airflow in current jet airliners is much faster than normal indoor buildings. Half of it is fresh air from outside, the other half is recycled through HEPA filters of the same type used in operating rooms. Any remaining risk to be managed is from contact with other passengers who might be infectious. Seat backs provide a partial physical barrier, and most people remain relatively still, with little face-to-face contact.

Despite substantial numbers of travellers, the number of suspected and confirmed cases of in-flight COVID-19 transmission between passengers around the world appears small (approximately 42 in total). In comparison, a study of COVID-19 transmission aboard high-speed trains in China among contacts of more than 2,300 known cases showed an overall rate of 0.3% among all passengers.

Onboard risk can be further reduced with face coverings, as in other settings where physical distancing cannot be maintained.

Risk reduction steps by airports and airlines

Steps being taken at airports and on board can include temperature testing and/or asking about symptoms (fever, loss of sense of smell, chills, cough, shortness of breath); enhanced cleaning and disinfection; contactless boarding/baggage processing; use of physical barriers and sanitisation in airports; physical distancing in airports and during boarding; use of face coverings or masks; separation between passengers on board when feasible; adjustment of food and beverage service to reduce contact; control of access to aisles and bathrooms to minimise contact; limiting exposure of crew members to infection; and facilitation of contact tracing in the event that a passenger develops infection.

Additional steps being studied are pre-flight testing for COVID-19 and adjustments to quarantine requirements.

Steps passengers can take

Wear a mask, don’t travel if you feel unwell, and limit carry-on baggage. Keep distance from others wherever possible; report to staff if someone is clearly unwell. If there is an overhead air nozzle, adjust it to point straight at your head and keep it on full. Stay seated if possible, and follow crew instructions. Wash or sanitise hands frequently and avoid touching your face.

Conflict of interest disclosures

Dr Pombal reported being an employee of TAP Air Portugal Group Health Services and is chairperson of the Aerospace Medical Association Air Transport Medicine Committee. Dr Hosegood reported being an employee of Qantas Airways and is president of the International Airline Medical Association. Dr Powell reports receipt of personal fees from the IATA.


[link url=""]'Bad math': Airlines' COVID safety analysis challenged by expert – Reuters article[/link]


[link url=""]Flight-Associated Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 Corroborated by Whole-Genome Sequencing[/link]


[link url=""]In-Flight Transmission of SARS-CoV-2[/link]


[link url=""]Transmission of SARS-CoV 2 During Long-Haul Flight[/link]


[link url=""]Air travel in the time of COVID-19 – The Lancet[/link]


[link url=""]Risk of COVID-19 During Air Travel[/link]



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