MurrayM:

 

it sounded a bit strange that they were only contacting the people that were sitting a couple of rows either side of the infected passenger. Don't they realise that people get up and walk around the cabin to stretch their legs, go to the toilet, etc?

 

I had read that someone who worked on a cruise ship was asked how the best way they avoid getting ill. They said they never touch their face with their hands, and they regularly wash their hands. If this person on the plane that was ill went to the toilet, which is almost certain, they touched the door handle, and so would a lot of other people who used that particular toilet. That could also help explain why in real life conditions, the spread around a plane can be quite random.