Last updated March 28, 2018 at 1:28 pm
Planes might seem like a hotbed of infectious diseases, but now we know how they spread around aircraft.
Every year, 3 billion people take flight worldwide. With increasing demand for air travel in China, the sub-continent and Africa, that number will steadily increase in the coming years.
While it might mean more flight options for your next getaway, it also increases the chances of infectious diseases spreading around the globe.
Despite sensational media stories and anecdotes, the risks of transmission of respiratory viruses from person to person in an airplane cabin are rarely studied and the risks poorly understood.
Using 10 transcontinental US flights, researchers have now worked out just how viruses spread around aircraft cabins… and it’s not quite as terrifying as you might have thought. In fact, you could be more at risk from the flight attendant than your fellow passengers.
Sniff and splutter
Respiratory diseases such as influenza are transmitted primarily over short distances through tiny droplets of water from sneezing and coughing.
Although disgusting, this means that the distance of transmission is relatively short, but that passengers and crew moving around the cabin will potentially infect more people by bringing more people into close contact.
The team from the Georgia Institute of Technology kept watch during their flights across the country, keeping a record of passenger and crew movements. They then used this information to model influenza transmission during their flights, using the example of an infected person seated in the middle of economy.
They found that passengers seated within one row forward and behind, and within two seats to either side of the infected passenger had an 80% or greater chance of becoming infected, according to the model.
For all other passengers, the probability of infection was less than 3%.
An infectious crewmember on the other hand would infect an average of 4.6 passengers per flight.
Actual risk is small
The model was based on the movement and behaviour of passengers and crew during flight, combined with known knowledge of how influenza spreads. However, during the 10 flights used to build the model, the team only observed one person coughing on board, out of 1540 total passengers, and none were seen severely coughing.
Likewise, no cabin crew were noticed to be coughing during the flights.
To find out whether they were still likely to have been exposed to any viruses from people not showing any symptoms, the team also collected 229 air samples during the flights. Although eight of the flights were during Influenza season, all of the samples returned negative results for 18 common respiratory viruses.
Part of the reason the actual risk is small is due to the air filtering occurring continuously on board. According to Boeing, the air in a 737 – the most common aircraft in the world – is completely changed every two to three minutes. During this time it is filtered to remove between 94 and 99% of airborne microbes.
Cabin crew policies are also strict on minimising the infection risk to other staff and passengers, by encouraging infected crew to stay away from work.
In the case of this study however, the researchers will need to to carry out further studies to capture more flights with sick passengers on board.
How to avoid getting sick
There are still actions that you can take to minimise your risk of infection. After all, no one wants to be arriving to the perfect sandy beaches of the Maldives and be stuck inside nursing a cold.
Of course, it’s impossible to choose everyone who is sitting nearby and avoid anyone who might be sick, but if we take the “red zone” calculated by the study – one row forward and back and 2 seats to either side – it is possible to work out on the plane where the lowest risk seat would be.
Most airlines in the world have a standard seat pitch – the row-to-row spacing of seats – of 31-32 inches in economy, and a width of around 17-18 inches. The means the “red zone” is an area 65 inches front to back, by 100 inches wide – an area covering 14 people in addition to yourself.
To minimise the risk, you’d want to minimise the number of people within that zone around you who could infect you.
Immediately, sitting against the window halves your red zone, making it 60 inches by 50 inches to one side only. In economy, this reduces the number of potential infectors in your red zone to 8 people.
The next risk identified by the study is people moving around the cabin. By sitting by the window you have maximised your distance from the aisle, but you still need to worry about someone heading towards the bathroom.
To reduce your chances of someone walking along the aisle, choose your window seat furthest from the toilets. In general, cabin toilets are at the rear of the cabin or each seating block, so move as far forward as possible.
As an added bonus, for wide-body aircraft such as the Boeing 777, Airbus A330, and Airbus A380, the front row of economy will often have a solid bulkhead in front, which then also reduces the number of people in your red zone to 5, by removing the row of people in front.
In general and using the information gathered by the Georgia Tech researchers, the very front corner will be the seat with the lowest chance of infection. The worst? Back row aisle by the toilets.
However, for maximum infection protection – the same strategies applied in Business Class reduce your red zone to 3 on a Boeing 737. On a widebody, and using the Qantas A330 as a model, you will only have 1 person in your red zone.
And splashing out for First Class – you may end up only needing to worry about the flight attendant.
Despite all the seat strategy, it is still important to maintain good health yourself – a healthy body will have more chance of fighting off an infection. However, most vitamins are thought to be pretty useless unless someone is actually deficient.
“The general conclusion from the scientific reviews are that for the average person, there’s no benefit in taking [Vitamin C] regularly during winter for prevention, and the benefits of taking it when you have a cold are sort of minimal,” Dr Ken Harvey from Monash University told the Sydney Morning Herald.
Also, pay attention to what is around you. As well as breathing in aerosols, another risk of infection is from touching infected surfaces, like the tray table or surfaces in the toilets. Many experienced flyers will use disinfectant towels to wipe down nearby hard surfaces after taking their seat, and it’s not uncommon to see some using alcoholic hand gel to kill any bugs after using the bathroom.
The research has been published in the Proceedings of the National Academy of Sciences