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旅行者可同时报告多种病症。陆地度假行程中未报告晕船（sea sickness）相关案例。请注意，由于样本量极大，即便微小的效应也会呈现统计学显著性，因此我们选取了P值。