Most Cruise Lines are very strict when it comes to their required medical examinations. Its simple really. If an applicant / ex-crew has been diagnosed as "MEDICALLY UNFIT", regardless of the nature of his / her being unfit, shall not be allowed to board the ship. If the crew is already onboard but has been diagnosed as "medically unfit", he / she shall be repatriated the soonest time possible. If you think that this practice is discrimatory or the sort, you may want to check out the Maritime Law.