A cruise can be a fun, relaxing way to spend a vacation, but any vacation spent with the flu is no vacation at all. Since a large number of people can come into close contact with one another on cruise ships, respiratory viruses, including flu, have the potential to spread easily on cruises. While not uncommon, recent cruise ship flu outbreaks have prompted CDC to remind travelers to get a flu vaccination and to take other preventative actions, both prior to and while on a cruise.

“Make sure you’re up to date on your flu vaccination before traveling on a cruise,” says Dr. Nancy Cox, director of CDC’s Influenza Division. “It’s good practice to check with your doctor at least 4 to 6 weeks before traveling to discuss vaccines you may need or medicines you should take while on a trip.”

Respiratory outbreaks on cruises, including those caused by influenza (flu) viruses, are not uncommon. Cruise ship travelers originate from both the Northern and Southern Hemispheres, which have opposing flu seasons. This means that flu outbreaks on cruise ships can occur year-round. CDC recommends a yearly flu vaccine as the first and most important step in protecting against influenza viruses. People taking a summer cruise who were vaccinated during the previous season will still be protected and will not need to get vaccinated again until the upcoming flu season. However, people who haven’t been vaccinated during the previous season and who plan to travel during the summer should get vaccinated. It’s important to get vaccinated at least 2 weeks prior to the cruise. It takes about two weeks after vaccination for protective antibodies to develop.

A typical cruise ship carries approximately 2,000 passengers and 800 crew members, and cruise ship capacities continue to increase and can exceed 5,000 passengers and 2,000 crew. “Getting a flu vaccine is equally important for cruise ship staff,” Cox says, “so as to prevent them from spreading the illness to their passengers and each other.”

People infected with flu may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick. That means passengers and crew members can spread the flu to someone else before they know they are sick.

In addition to vaccination, everyday preventive actions, such as washing hands often with soap and water and covering coughs and sneezes with a tissue, are also important while traveling to stop the spread of germs. Symptoms of flu can include some or all of the following: fever or feeling feverish, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headache, fatigue (tiredness), and sometimes diarrhea or vomiting. Not everyone with the flu will have a fever. People who experience any of these symptoms while on a cruise should visit the ship’s medical facility.

Trained medical staff can evaluate passengers for flu, provide care, and prescribe flu antiviral medications if needed. Antiviral drugs are prescription medicines (pills, liquid or an inhaled powder) that can make illness milder and shorten the time people are sick. Antiviral medications are most effective if used early within the first 2 days of symptoms. Cruise ship medical personnel are advised to treat passengers with flu illness who have severe illness or who are at high risk for influenza complications with antiviral drugs as soon as possible.

• Travelers who become ill on a cruise should rest and stay in their room, away from other passengers, so as to prevent the spread of disease.
• Travelers who have recently been sick or become sick at the time of planned travel should postpone travel until they are feeling better. CDC specifically recommends people wait at least 24 hours after their fever has resolved without the use of fever-reducing medications before traveling.
• Traveling while you are sick may put your health at risk or put others around you at risk of getting sick. While sick, passengers should limit contact with others as much as possible to keep from infecting them. Cruise ship staff often will separate ill passengers from other passengers for the duration of their illness.
• Travelers who are still sick at the end of their cruise should consider delaying further travel on airplanes, buses or trains to avoid infecting others.

For more information on preventing and managing flu illness while traveling, visit CDC’s seasonal flu and travel page http://wwwnc.cdc.gov/travel/page/seasonal-flu-travel.htm. For CDC recommendations regarding actions to take prior to going on a cruise, see Cruise Ship Travel: Recommendations from Health Information for International Travel at http://wwwnc.cdc.gov/travel/page/air-travel-cruise-ships.htm. For more information about the flu, including the latest on flu activity, see www.cdc.gov/flu.