This is a form of gastrointestinal illness which usually causes nausea, vomiting and diarrhoea. People with it can also have headaches, fever and stomach cramps. It is also common on land with up to one in thirty people suffering it every year. As it is contagious, and spreads easily through touch, it tends to get a lot of publicity and coverage when it breaks out on a ship. It spreads fast when passengers are not disciplined about hand washing and sterilising, and so lines suggest strict cleansing habits.
Cruise lines take many steps to prevent an outbreak which include having passengers sign a declaration that they have not suffered from vomiting or diarrhea for 48 hours before boarding, asking them to wash their hands frequently with soap and water, and to use the alcohol gel available around the ship and by regular sanitizing of handrails, elevator buttons, and other equipment handled frequently by passengers. These steps ensure it is unusual to come across the problem while cruising. I, for example, have only encountered two outbreaks on a ship in the last decade and was not affected by following the advice to avoid it.
Take care, follow the advice and wash your hands with soap and water properly (one tip is to sing “happy Birthday”to yourself while doing it as that take the right amount of time required).