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What SARS and 5 deaths on Air China Flight 112 showed about disease transmission whilst flying

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Whilst we haven’t covered it, there has been quite a bit of discussion in recent days over easyJet’s plan to leave all middle seats empty when it resumes flying.

The airline believes that its plan will reduce the risk of coronavirus transmission on board.  In reality, I think that easyJet knows that it won’t be selling more than 2/3rd of its seats for quite a while and that this is simply easy publicity to reassure people.

If it does reassure you, it possibly shouldn’t.

We have been here before, with SARS.  In particular, the infamous (if you’re a clinician) case of Air China flight 112 from Hong Kong to Beijing in March 2003.

The flight length was three hours, which is worth bearing in mind as you read on.  Until this flight, it was assumed that mass infection would require a minimum flight time of eight hours and that only passengers within two rows of the source were at risk.

Take a look at this image.  This is taken from Flyertalk.  I can’t find the original source but there is an identical seatmap – just not as easy to follow – in The New England Journal of Medicine here.

Air China flight 112

What you can see from this seatmap is that, in Row 14, was a 72 year old man with an active case of SARS.  He later died.

The general view at the time, as shown in the pink area, is that anyone who was sitting within two rows of an infected person – in front or behind – was at risk.

However, as you can see from the dots, passengers were infected up to seven rows from the infected passenger.  In total, 22 people were infected with SARS during the flight and five died.

(There are not 22 dots on the image above because it was not possible to confirm where two passengers had been sitting.  The total of 22 also includes two members of cabin crew.  These two members of cabin crew were both from Mongolia and were belived to be directly responsible for a further 300 infections in Mongolia.)

To put this in context, total global deaths from the 2003 SARS outbreak totalled 774.  This single flight accounted for 0.65% of global deaths, excluding the original infected passenger.

All 22 infected people developed symptoms within two to eight days of the flight.  None had any known additional exposure to anyone with SARS.  Whilst some of the infected passengers were travelling together, only one of the 22 cases developed so late (eight days post flight) that it could potentially have been due to secondary infection.

Air China flight 112

It isn’t that simple of course …..

The New England Journal of Medicine report is worth reading, because it also looks at two other flights taken by known SARS carriers.

One flight, which had four known carriers on it, only led to one additional infection.

A second flight, with a passenger who was not showing symptoms at the time of travel, led to no additional infections.  This flight was carrying 315 passengers on a Boeing 777.  74 passengers were interviewed directly to confirm they had no symptons and enquiries were made into the health of the others.

You should not assume that it is unavoidable that an infected person will infect others whilst travelling.

Here is a relevant paragraph from the report above about Flight 112:

The risk of illness was related to the proximity to the index patient, with illness reported in 8 of the 23 passengers who were seated in the same row as the patient or in the three rows in front of him, as compared with 10 of the 88 passengers who were seated elsewhere (relative risk, 3.1; 95 percent confidence interval, 1.4 to 6.9). It is notable that 56 percent of the passengers who became infected were not seated in the same row as the index patient or in the three rows in front of him.

In terms of actual seating:

There was no significant difference in risk between persons seated in an aisle seat and those seated in a middle or window seat (6 of 39 [15 percent] vs. 12 of 72 [17 percent]; relative risk, 0.9; 95 percent confidence interval, 0.4 to 2.3). Two of the 20 passengers who became infected (and whose seating assignments are known) were seated within 0.9 m (36 in.) of the index patient.

The fact that most of the infected passengers were sat in front of the index passenger is what would have been expected for a disease spread by droplets released during breathing.  This should not have impacted passengers more than three feet from the infected passenger, based on assumed guidelines, but more than 90% of infected passengers were sat further away than this.

There are, of course, other potential ways in which passengers could have been infected – during or immediately after boarding, after disembarking at immigration or baggage reclaim, or moving around the aircraft during the flight.

Air China Flight 112

It’s not all bad news ….

The good news, to some extent, is that Flight 112 has become infamous simply because it is so rare.  The passenger involved is believed to have been a ‘super spreader’ who was substantially more likely than average to infect others.

The New England Journal of Medicine report concludes that:

It seems likely that the overall risk to airline passengers is quite low. As of May 12, 2003, the WHO reported that 35 flights were under investigation because a patient with symptomatic SARS had been on board, but only 4 of these flights were deemed to be associated with possible transmission.  Aircraft ventilation systems are believed to be highly efficient at keeping the air free of pathogens, which they do by exchanging the air in passenger cabins every three to four minutes and passing the circulated air through high-efficiency particulate-arresting (HEPA) filters designed to filter out all particles larger than 0.3 µm by 1 µm.

Comments (153)

  • Riccatti says:

    I am sorry to say it but people of age are an elevated risk. Not only to themselves but being more contagious on average. They also more prone to overlook/ignore symptoms.

    If you look into case studies of traced contacts in Korea and Singapore, it is hard not to observe that most super-spreaders (we talking hundreds of cases stemming from one person) were >60 years old people who visited public places — a hotel for buffet breakfast, churches. Some were doing it while already complaining about symptoms.

    • Anna says:

      How does being older make you more contagious?

      • Riccatti says:

        You carry and exert the higher viral load (for several reasons).

        The super-spreaders tend to be of age > 60. The other super-spreaders are in positions such as shop assistant.

    • Nick_C says:

      Education for the masses in places like Korea and Singapore has improved dramatically over the last 50 years. Old people in these countries may not be as well educated as younger people, and may not understand the importance of behaving appropriately to reduce the risk of spreading the virus.

      In the UK, I would suggest that the opposite is true.

      • Riccatti says:

        @Nick_C This is a mere conjecture.

        The point is not about education or that older people from Korea are uneducated. People who are in their 50es now already grew up with a decent access to the higher education.

        First, look at the %% of older people travelling.

        Second, this is all very subjective. Educational level will not be a predictor of reasonable, quarantine behaviour (take cases of the Government’s chief scientific advisors and Imperial College professors — they could have worked with data and papers from home (however important that data is), but they chosen to go to offices).

        Older people are simply more prone to ignore the symptoms, get up and go — if they have an appointment, or travel scheduled.

        • the_real_a says:

          In asia particularly older people are likely to be revered if behaving badly. In the west they are likely to be called out and told to change their behavior.

        • Nick_C says:

          Taking findings from a study in Asia and assuming the same will apply on the UK is mere conjecture.

      • Karen Brown says:

        +1

    • Lady London says:

      I’m going to be flamed here. But with my limited Asia experience I’ve noted that older people in Asia seem far more prone than younger or elsewhere, just to hawk everywhere or cough or sneeze ove literally everyone for mike’s without making any effort to cover up.

      • Nick_C says:

        I’m not sure you can generalise about Asia. The Chinese seem to spit more than we are used to in the UK, but not the Japanese.

        Sadly, its a disgusting habit that is becoming more prevalent among young Brits as well.

        • Lady London says:

          I’ve been in Chinese-ethnic locations in 3 or 4 countries in Asia, and Indonesia and Thailand which is what I based my comment on.

          Also been to Japan and wasn’t really thinking of Japan either, when I said that.

        • Cat says:

          Yes, it is, especially during exercise! It’s vile!
          I’ve been climbing up and down my building (seriously, going outside is more stress than it’s worth right now), and encountered someone’s gob on the stairs, as I was climbing yesterday.
          Ewwww.

  • Andrew says:

    New Years Eve 2018 I picked up an eye infection after flying from EDI to LHR.

    Or did I?

    At some point, I’d touched a surface with the relevant bacteria and touched my eye. So I went through the process of where I’d been and what surfaces I’d touched. Lift to station from a family friend, but didn’t take my winter gloves off. Took gloves off to buy ticket from machine at Stirling station, passed through barriers, used lifts as I had luggage, gloves still off. Gloves back on on bitter platform. Was bacteria now inside gloves?

    I could go on for paragraphs but the journey was:-

    Car – Lifts – Train – Lifts – Tram – Luggage Drop off – Escalator – Security
    Buy lunch – loo break and wash hands – Eat lunch
    Loo before boarding – Flight – BoB
    Escalator – Luggage collection – Lifts – Underground Transfer to T2
    Lifts and travellator to car park pick-up – minibus to car park
    Drive to supermarket, trolley, self service check out drive home via Petrol Station.

    Wherever I picked it up, it was 9 months until I could wear contact lenses again, even now I’m still just wearing them a 3-4 days a week instead of 6.

    • J says:

      This is my worst nightmare! I also hate my glasses. Glad you’re OK now though.

    • Novice says:

      Makes me think it’s going to be very hard for me to actually go on a holiday after this situation.

      I already have OCD and always was hyper vigilant in cleanliness even whilst travelling but at least I could manage before but now reading about ppl licking bread etc (which I didn’t know) makes me never want to travel again.

      I probably need a private jet in future 😂

      • Anna says:

        I think the licking bread thing was a joke! (unless the cabin crew allow this to go on unchecked).

        • Novice says:

          Well I hope so. Although I have always only accepted bread if I see the crew using tongs to hand it as I myself always use hand sanitizer before touching food and also wipes.

          I can’t remember which flight, but once the bread was pre- packaged.

          However, my fellow travellers have never given me much confidence as before this I had hardly ever even seen ppl wash hands after using toilets. That’s the reason, initially I actually got happy because the virus had made humanity discover the thing I had always known; to wash hands.

          But it’s all about habit. I don’t believe ppl are washing as much as they should hence the spread.

          • Nick_C says:

            It’s not just a question of washing your hands after going to a public toilet. The design is usually totally wrong. You usually have to touch two door handles to get out of a public loo. the old trick of using a paper towel no longer works as they have disappeared.

            There are exceptions of course, and large toilets at UK airports are exemplary with no doors and automatic taps and soap dispensers. Unfortunately though, properly designed public loos are still quite rare.

          • RussellH says:

            In many cases, building regs in the UK demand 2 doors to get in/out of a public loo. Always in restaurants in the UK. We cannot have the meerest possibility of someone getting there slightest glimpse of what is happening inside the loo, which would be possible if there were only the one door!

          • Lady London says:

            The trick @Nick_C is to provide your own tissues (why do you think us ladies always have tissues in our handbags? we don’t have colds or need to touch up our makeup that much).

            Or, always ascertain the presence of paper (that you don’t have to reach inside anything to get) or hand towels that you ensure are there before operations commence.

            This is standard for us ladies. I have a map in my head of all the places I regularly go in London and superimposed on that map is the location of every “good loo”‘s location. Us ladies need to keep track of such things as we can’t just disappear round a corner for a minute and do anything necessary. The same for carrying paper/tissues.

      • Riccatti says:

        Put OCD to a good use: make sure hands avoid face contact.

        • Novice says:

          I already did all these things that are now guidelines but I’m afraid I can’t control other people so I managed my OCD by telling myself it’s all about choices. Eg. In lounge if I see cold food or snacks without tongs, I only have hot food.

          Or wait for a new food tray to come out and try to be first. Try to always fly business do less ppl.

          Recently I had to take a Jet2 flight because there was no other option on the day and time and it was like an extreme test of my OCD. It was horrendous.

      • Peter North says:

        You’ll be in good company on this site with the number of obsessives there are on here!!

      • Ian says:

        Thought for the day: I’m sure we’ve all heard of people who’ve given up flying altogether because they’re convinced it’s dangerous and one day their aircraft will crash. Tragically, I knew of one person who gave up flying to always go by train (yes, very safe) but was killed in a car crash on the way to the station. Although we can all try and stay as safe as we can, nothing in life is certain – except that one day it will come to an end.

      • Lady London says:

        You are in good company here at HfP @Novice. The wanting a private jet referenc qualifies you 🙂

    • Peter K says:

      Having some knowledge in this field and the severity of the infection you describe, it sounds like the infection was not caused in the manner you feel likely.
      Of course I do not know the full details, and maybe it was transmitted on the trip, but it’s more possible that you, for example, got water in your eyes while wearing contact lens (eg
      showered while wearing them or went in a jacuzzi) or slept in them (even if they are licensed for such use).
      It would need to be a particularly severe infection such as acanthamoeba or pseudomonas aeruginosa which is unlikely to have been transmitted by hand hand to eye contact for a few seconds.

  • Martin says:

    That’s why everyone going to the plane should be wearing masks.

    • Riccatti says:

      Masks on the plane make sense but we are talking short-haul.

      If that avoids cramming people at a destination for hours in a tight, hot, unventilated corridor “for a temperature check”. I am 100% confident the same people who do airport security will make a complete and counter-productive and more dangerous circus out of it.

      Also those with symptoms or fewer or difficulties breathing are bound to be the worst offenders by taking masks off or just shifting them a bit upwards.

      • Novice says:

        True.

        In my young life experience, I have noticed the people who cause things are usually the ones who logically you wouldn’t think would.

        Prime example is Boris, our PM getting infected because he thought it’s great message to shake hands with patients and now he’s dodging scrutiny in his holiday home instead of face the questions about PPE etc.

        At least I know OCD ppl have never caused anything if their OCD pertains to washing hands obsessively.

        • Unsavage gerbil says:

          I bet your about 45 really.

          • Novice says:

            I wish. I would have been to all the countries that I wanted to tour by that age abd I could have chilled in the knowledge I had done most of the things on my bucket list.

            That’s why I’m annoyed it happened now when I’m still young.

            Then you have some people like simon reeve and the great David who have been all over the place and nothing affected their travels. I’m jealous but they are both awesome so good for them.

            In 5/6 yrs time I’ll resume my travels I guess.

        • Pete says:

          @Novice. Having a family member with OCD re: cleanliness and avoiding micro-organisms (eg will not touch food that had been touched by anyone’s hands including their own) etc, I can say they are very poor at avoiding passing on infections. This is because they are worried about themselves getting an infection but not others getting it from them.
          As you say “the people who cause things are usually the ones who logically you wouldn’t think would.”

          • Novice says:

            I can understand but thankfully I’m not classed as extreme I think.

            And I can assure you. To my knowledge I have never passed anything to any family and friends.

    • Fred Bloggs says:

      What sort of “masks”? The ill fitting cloth or fabric ones with pore sizes many times larger than the virus are useless. Tight military style masks would be better, provided they are not removed.

      • J says:

        Those kind of masks you describe may still be of some use in limiting how much an infected person is spreading the virus – and certainly better than nothing. This is the thinking behind Germany making masks compulsory on public transport. The UK though I think with its inability to procure enough masks for the NHS will be more guided by that than anything else.

        • Lady London says:

          Even ordinary glasses help to wear too if you are concerned enough to wear a mask.

      • Cat says:

        They’re not useless. There are clearly much better masks, and nobody in healthcare, who is being exposed to high viral loads on a daily basis, should have to wear one, but they can still help stop the spread.
        See the Nature article below.
        https://www.nature.com/articles/s41591-020-0843-2

    • AJA says:

      Re masks,; Thinking a mask is going to stop Covid-19 is the same as thinking that your underpants will protect everyone from your farts.

      • Pete says:

        But it would be worse if someone was walking around naked!

      • J says:

        No it’s not. There are proven benefits that masks in association with a number of other measures are effective in helping reduce the spread of the virus. Nobody is saying masks alone are the answer. Unfortunately I think your attitude is widespread in the UK, which is another reason why the UK will fare so badly in this crisis.

      • Lady London says:

        @AJA I never thought I would read that on a frequent flyers comment page….! 🙂

  • Nige says:

    I’d assumed that passenger numbers would increase not as people were reassured they wouldn’t catch it but as an increasing proportion of the country had already had it and assumed (rightly or wrongly) that they wouldn’t catch it again. I’m not sure people trying to avoid ever getting it are the target audience since they’d need to isolate for 18 months til vaccine anyway.

    • Novice says:

      Vaccines are not guaranteed to work as I have read that this virus has already 19 new genomic mutations as it has mutated into different strains.

      However the report was from Chinese University so I don’t know how much of it is actual fact. And then it also depends on article sources etc.

      But I guess I’m not holding my breath for vaccines just yet.

      • RussellH says:

        The prof from Imperial on the Today programme this morning said the CV is remarkably stable, compared with flu (about 100x more variable) or HIV (off the scale).

        • Rob says:

          I read the same somewhere, either Times or Guardian today.

          • Novice says:

            Well I’m more likely to believe our own doctors tbh than any Chinese information due to the well reported fact that they silence the whistleblowers.

            But my conspiracy theorist side is very suspicious of everything atm hence thinking I should probably resume travel in a few yrs time… if I’m still living 😂

          • Lady London says:

            You ARE my long lost twin @Novice.

  • Nun says:

    Isn’t spreading likely by touching seats, armrests and trays? The way you’ve written this implies it’s somehow the breath of nearby passengers.

  • Charlieface says:

    22 deaths is still in the article page header (that shows in the tab title)

  • Dimitri says:

    “Aircraft ventilation systems are believed to be highly efficient at keeping the air free of pathogens”

    This sounds like the ventilation system for that particular aircraft was not working properly.. Has anybody thought of that?

  • Prins Polo says:

    Also think about the Vietnam Airlines flight where a single person infected a high number number of other business class pax (I can’t recall the precise numbers, but think it was 11 pax out of the total of 22 in J).