Aches on a plane … research shows flu isn’t easy to catch
▶ Catching a cold on a plane can happen, but anyone ill on arrival caught the bug before stepping on the plane in the UAE, writes Daniel Bardsley
Many of us would have wondered what germs we are breathing in while sitting in an aircraft, with hundreds of passengers seated for hours on end sharing the same air in the cabin.
The recent Emirates flight from Dubai to New York, in which passengers became ill with flu-like symptoms, highlighted those concerns, whether justified by the evidence or not.
Reports in the US indicated that up to 106 people on flight EK203 complained of symptoms such as coughing and fever when the Airbus A380 landed at John F Kennedy Airport on Wednesday morning.
Emirates said that three passengers and seven crew were taken to hospital for tests. Authorities later confirmed that they tested positive for influenza, or the common cold, but nothing more serious.
But doctors could be sure of one thing: anyone ill with flu on arrival in New York must have contracted the virus before boarding the aircraft in the UAE.
The incubation period – the time between exposure to an infection and symptoms developing – is much longer than the almost 15 hours it takes to fly between the two cities.
“It’s got to take a couple of days minimum and usually more,” said Peter Openshaw, a professor of experimental medicine at Imperial College London, who was a member of the UK Department of Health’s scientific pandemic influenza panel from 2006 to 2015.
This raises the question of why so many people on the flight felt ill.
Prof Openshaw said mass hysteria could cause large numbers of people to think they were unwell.
But the influenza virus can spread between people on aircraft.
“There’s evidence of transmission, particularly near the toilet because everyone goes to the toilet and may be leaving infected material on door handles,” Prof Openshaw said. “It’s not impossible for outbreaks to happen as a result.”
There are several ways in which the influenza virus can spread on aircraft, including inhaling infected particles – but the risks are probably lower than we imagine.
Prof John Oxford, co-author of the textbook Human Virology and an emeritus professor of virology at the University of London, said filtering systems kept the air on planes clean.
Passenger planes are typically fitted with high efficiency particulate filters, which are the same type found in many home air purifiers. Recirculated air is also mixed with air from outside.
“A lot of infective bacteria and viruses are filtered out,” Prof Oxford said. “Your best chance of getting infected is not on the flight, but queuing up for a taxi.”
The main risk, he said, was to those sitting within a few feet of an infectious person.
Results released by scientists from Emory University in the US indicated that the likelihood of transmission to those further away was “low”.
Infectious cabin crew members, because of the number of passengers with whom they interact, may infect several people. The researchers found that an ill crew member was likely to infect an average of 4.6 passengers.
People sitting next to a window are at lower risk of infection than those in middle or aisle seats.
There have been “extremely unusual” cases, Prof Oxford said, where the air-conditioning system broke down and large-scale infections resulted, but there was no evidence of this with the Emirates flight.
One much-discussed instance of influenza transmission happened in 1977, when an Alaska Airlines Boeing 737 had an engine failure while trying to take off, and sat on the tarmac for three hours.
Although the air-conditioning system was broken, most of the 54 people onboard remained in the aircraft.
A scientific paper in the American Journal of Epidemiology said that within three days, almost three quarters of passengers developed symptoms such as coughing, fever, headache, sore throat, muscle pain and fatigue – all from a single infected passenger.
There have also been cases where other infections such as severe acute respiratory syndrome, or Sars, and swine flu, caused by the H1N1 virus, have spread on board an aircraft.
Further research and improved reporting of onboard infections is needed to better understand the risks, Katrin Leitmeyer and Cornelia Adlhoch, from the European Centre for Disease Prevention and Control, concluded in a 2016 paper in the journal Epidemiology.
“There is evidence that influenza transmission aboard aircraft occurs but the published data does not permit any conclusive assessment of the likelihood and extent,” they wrote.
Those concerned about what pathogens they might be exposed to can reduce the risks. Keeping the overhead air vent open is one measure, as it leads to better flow of clean air. Not rubbing the eyes or nose is also advised.
People at particular risk of serious illness when exposed to influenza, such as those with asthma, chronic bronchitis or diabetes, might consider preventive drugs, Prof Openshaw said.
Oseltamivir, sold under the brand name Tamiflu, can prevent flu.
“That’s been demonstrated to prevent infection if taken by people who have been in contact with someone with influenza,” he said.
To reduce the likelihood of infecting those near by, ill passengers should keep their overhead air vent open to blow infectious particles towards the floor. Wearing a face mask can also reduce the chanced.
It is worth remembering, though, that the global media coverage the Emirates flight attracted was not caused by onboard infection.
“It’s just bad luck it got a lot of publicity,” Prof Oxford said.
The incubation period for flu is much longer than the 15 hours it takes to fly between the cities PETER OPENSHAW Professor of experimental medicine at Imperial College London