Disease frequency in travellers on land- and cruise-based holidays.

Travellers could report more than one illness. Sea sickness was not reported from land based holidays.
Please note that because the sample size is very large and therefore even small effects will appear significant we have chosen P<0.0005 as a cut-off value compared to p values used in other smaller studies (i.e. P<0.01). Our judgement is that the differences between land and cruise based are significant for cold, sunburn and stomach upset are significant, but the difference is probably not big enough to be important for colds, whereas it is for sunburn and stomach upset.