There's nothing worse than being sick on vacation. You're not in your home. You're not in your bed. People are around you and you want to be alone. You want to be out doing all the things you had planned and now you're in a hotel room. Yuck!
Prior to travel, I recommend visiting the Centers for Disease Control and Prevention website. Their Resource for Travelers section will give you everything you need to know and then some.
Lately, a slew of stories started floating around online about people getting sick on cruise ships. It's cold and flu season and people get sick. It's a fact of life. The headlines sound horrendous. 500 people sick onboard XYZ Cruise Line. 500 people out of 8800 onboard is .056. Less than 1%. Even ships that scored a 100% on their recent sanitation inspection have had sick passengers. People bring illness with them. They may not be showing signs at embarkation. To assist in not passing on anything to other passengers, when you are questioned at embarkation if you have had any signs of illness. Don't lie. The cruise line will most likely not prevent you from traveling. They may quarantine you for your 1st day if your symptoms warrant.
As with leaving your home to go anywhere during cold/flu season, take the necessary precautions.
I wish you safe and healthy travels!