Just want to add a couple of comments:

1. Getting symptoms of a respiratory tract infection at the end of, or shortly after, a long-haul flight, the risk is considerably larger your fellow traveller in the elevator en route to hotel check-out, hours before the flight, who coughed/sneezed, is the source. But the careful selection of pax travelling in your cabin of choice having enough common sense to cancel their flights, or wear appropriate masks to protect you from sharing their infection, is of utmost importance.

2. Even though I often swipe my tray table and armrest, my main reason for that is not disease protection, but mainly because they are areas which I touch with my hands, where items/drinks etc, later ingested, might catch dirt I'd rather avoid. Although, both bacteriae and viruses tend to be more common in dirty places.

3. Although not really feeling the high risk of getting viral gastroenteritis when travelling, being short of 20 years since my last 'protuberance', it's good to have some statistical comparisons. For a person with intact immune system to get a pneumococcal pneumonia, you need to be infested with 250K pneumococcal bacteriae. Like being sneezed at right in your face. A person with viral gastroenteritis, who may have puked 30 min ago, who sneezes/coughs, sprays out micro droplets, that in a room with circulating air can be traced for 30+ minutes. Every single droplet contains 1.5+ M virus particles. How many is needed to get the infection? Just 15-20 ! Have that in mind when standing on the subway or in front of the check-in counter and someone behind you is sneezing.