A string of medical mysteries surrounding flights arriving in the US this week has put local aviation and public health authorities on high alert – but the threat of a disease outbreak here remains low, Australian experts say.

“It’s not so common to have so many people fall ill at the same time,”   Australian aviation medical expert Dr Kate Manderson said.

“It’s very rare for infectious diseases to spread on a plane. Cabin air quality is excellent, and air filtration on planes is better than operating theatres.”

According to the US Centers for Disease Control and Prevention (CDC), the recirculated air on newer model planes passes through a series of high-efficiency particulate air (HEPA) filters. At a rate of 20-30 times per hour, the filters make it a difficult environment for infectious diseases to spread.

Dr Manderson, a general practitioner and president of the Australasian Society of Aerospace Medicine, told The New Daily that while diseases can and do spread on planes it’s far more likely that the passengers became infected before flying.

“Incubation time [for influenza] is days not hours. It’s more likely that they pick it up before they get on the plane, even before they’re in the waiting area or lounge,” she said.

On Thursday afternoon (local time), 250 passengers and crew on two American Airlines flights arriving at Philadelphia underwent medical evaluation as a precaution after some travellers fell ill, an airport spokeswoman confirmed.

A dozen people on Flight 717 from Munich and Flight 755 from Paris reported flu-like symptoms, a day after 100 people reported a similar illness on an Emirates flight from Dubai to New York.

Follow-up testing in New York has since confirmed that 10 of the passengers aboard the Emirates flight had influenza or common cold viruses. The patients were all being released from hospital, a press secretary for NYC Mayor Bill de Blasio tweeted on Friday.

Follow-up tests complete: nothing other than influenza and some common cold viruses found. The patients are being released from the hospital. This’ll be my last Flu Plane tweet. Everyone remember to get their flu shots! https://t.co/cb6PqJBzWI

— Eric Phillips (@EricFPhillips) September 6, 2018

Rapper Vanilla Ice, who was a passenger on the Emirates flight, described the frightening scene when the A380 double-decker airbus landed at John F. Kennedy International Airport.

“When we started looking out of the windows we were like, this is much bigger than the pilot made it out to be, you know this is real serious,” Vanilla Ice, who is actually named Robert Van Winkle, told reporters.

“At that point I was starting to worry,” he said.

So I just landed from Dubai and now there is like tons of ambulances and fire trucks and police all over the place pic.twitter.com/i9QLh6WyJW

— Vanilla Ice (@vanillaice) September 5, 2018

The illnesses from the flights to Philadelphia, and the other to New York, are thought to be unrelated.

Best defence is vaccination

Professor MaryLouise McLaws, an infection-control expert at the University of New South Wales told The New Daily that the recent US flu plane scare doesn’t pose a high health security threat in Australia. However, she stressed that people should still do everything they can to protect themselves against infectious diseases while travelling.

“If you are going to travel you need to be mindful that some countries have multiple flu seasons. So it’s really important to get vaccinated,” Professor McLaws said.

“Your risk of getting seriously ill and dying reduces if you’ve had a series of flu vaccines. If you’ve been vaccinated for the current season and the season before that, your body is building a ‘memory bank’.”

Hapless travellers seated directly in front, behind or next to an infected person are most at risk of catching the virus.

But, studies show that the flu virus can spread up to 2.5 metres from the source.

And if you’re particularly unlucky, you may come across a ‘super spreader’ who has a high viral load, Professor McLaws said.

“When you’re talking or laughing you’re pushing out very tiny droplets on your breathe. You don’t even know you’re excreting it.”

“You’ll infect at least one person in that environment,” she said.

“Without vaccines it’s very difficult to control this clever little virus. That’s the problem every season.”

Air travel is a ‘healthy person’s game’

Dr Deb Mills, medical director of the Travel Medicine Alliance, a network of travel clinics around Australia, said travellers experiencing “unstable” symptoms shouldn’t get on planes, both for their own health and that of other passengers.

“It’s a healthy person’s game when getting on planes. I’ve got a patient now who has a fever and we advised that person not to get on a plane,” she told The New Daily.

Unstable symptoms may include fever, especially when you don’t know the underlying cause, chest pain, any sort of neurological symptoms, or unstable stomach upsets, to name a few.

Before travel, doctors advise seeing a GP about any worrying symptoms, as well as discussing appropriate vaccinations for your destination.

During the flight, it’s important to wash your hands regularly. Using alcohol gels and face masks can also help stop the spread but is not a full-proof defence, health professionals say.

Will I get stopped at boarding if I’m sick?

Airlines have the right to refuse boarding if a passenger is deemed unfit to fly, though it’s worth checking with your airline as rules can vary between carriers.

Dr Manderson said that part of the cabin crew’s role is to look for people who are showing signs of illness.

“It starts at check-in with ground staff, by asking if you’re okay. And then right up to the gate, they’re checking then too,” she said.

Someone with a runny nose is unlikely to get a second look, especially in wintertime. However, staff may pull aside travellers if they are showing more serious signs of illness, such as flushed or pale complexion, bleary eyed, sweating or confusion.