Even if you are not at risk for yellow fever, the CDC notes that some countries in Africa and South America require proof that you received the yellow fever vaccination. This is especially the case if you visited a country with yellow fever. Cruise ship policies may differ from those of their destination countries. Be sure to ask the cruise line or check online to ensure that you won’t be stuck onboard while your fellow cruisers are off exploring the port of call.

Stay Sanitized

When you consider that the average cruise ship carries 2,000-3,000 passengers, the odds are favorable that not one but many passengers will be ill. And when you factor in sharing pools, decks, chairs and other items onboard, as well as touching many of the same surfaces that they’ve touched, it’s logical to conclude that you will put yourself at risk of catching some sort of bug onboard.

The good news is that cruise lines are aware of these risks and take measures to limit the spread of diseases onboard their vessels. You’ll find hand sanitizer dispensers throughout the ship. A good rule of thumb is to stop and sanitize whenever you come across one. You may want to consider bringing travel-sized hand sanitizers onboard with you and using them frequently throughout the day while you’re using equipment, lounging in common areas, and before and after eating in dining halls. Frequent hand washing is also advisable. And if you are one of those people who climbed aboard despite having a case of the sniffles - you should be sure to offer your fellow cruisers the courtesy of sneezing and coughing into a tissue rather than your hand, or sanitizing after you do.

Keep Your Hands Off Your Face

Norovirus is one of the most notorious cruise ship viruses. It can cause nausea, vomiting and diarrhea. This virus and others can be prevented using the frequent hand washing and sanitizing measures outlined above (always look for a sanitizer that contains at least 60 percent alcohol). But one other thing that cruisers should be mindful of is how often they touch their faces.

Researchers at the National Institutes of Health have found that the average person touches his or her face an average of 3.6 times an hour. Every time you touch your face or nose, you’re transferring all of the bacteria and viruses that your hands have picked up by touching common surfaces (an average of 3.3 times per hour). This process is called “self-inoculation” and is the primary reason why germs spread from contaminated surfaces to infect people.