[kgwgk]

If you agree that they are not a random sample of the population - they are healthy enough to be fit for travel (like the majority of the population) you are not trying to contradict ant6n's comment as I thought. I misunderstood, my apologies.

[rvnx]

and it's not a small travel (e.g. the British tourists that went on board the Diamond Princess).

If you are not in good health at the beginning, you don't adventure yourself 10 hours+ from your home. So this group is likely in better shape than average population.