Your biggest worry about getting sick post flight is other people. “Holidays can mean mass transport and exposure to people in droves in transit and hotels,” says Professor Montgomery. “Disease patterns in travellers are different, for example when it’s summer in the UK, it’s winter in Australia where viruses are prevalent.”

And, if you fly economy, you’re probably more likely to pick up the germs as being squished in with passenger’s means infection is more likely, just like on the ground. However, the well-shared rumour that re-circulated air is the reason germs spread may not be true as plane filters decontaminate the air before it’s pushed back in the cabin.

Another study blames low humidity for post-flight sickness. Apparently the dry air interrupts our mucociliary clearance system, which consists of a thin layer of mucus and tiny hairs in the nose that usually trap viruses and bacteria. With this system down, the germs can get into your lungs better.

How to avoid a holiday illness – Professor Montgomery explains four easy steps