Part of the draw of a luxurious cruise ship is the ability to leave the land behind. Unfortunately, many infectious germs are not so easily abandoned.
One of these germs is norovirus -- a notorious stowaway on cruise ships that is responsible for several high-profile outbreaks each year.
The CDC identifies noroviruses as a common culprit of "stomach flu" -- technically referred to as gastroenteritis. Those infected with norovirus generally feel extremely sick and may vomit several times a day. In severe cases, vomiting and diarrhea can leave an infected person dehydrated and in need of medical attention.
"There continue to be three to four significant outbreaks per year," Freedman said. "The CDC considers a significant outbreak to be when more than 2 percent of people on a cruise come down with norovirus. One cruise last year had an 8 percent attack rate, so that's hundreds of people."
Fortunately, Freedman said, norovirus has been largely controlled through guidelines on ship sanitation and strict attention to hygiene regulations.
"The cruise industry has becomes absolutely obsessive with personal hygiene," he said, "specifically hand hygiene."
He noted that two of his colleagues who recently went on a cruise reported that they were not allowed into the dining area of the ship without being given a sanitary hand wipe.
Make sure to adhere to all recommended hygiene regulations on your ship, and you should be alright.
Additionally, Schaffner said that travelers who are planning to take a cruise can further protect themselves by ensuring that they have their own supply of sanitary wipes handy.
"Any of these alcohol-based gels or sanitary wipes, if you take some of them with you they will be available at all times."
When news broke two years ago that Atlanta attorney Andrew Speaker boarded an international flight even though he was infected with tuberculosis, outrage followed.
Since then, this scenario has repeated itself several times -- most recently on March 16 when the CDC announced that a passenger on a flight from Germany to Detroit had been diagnosed with tuberculosis.
"Tuberculosis has certainly been well documented to be transmitted on airplanes," Freedman said.
Fortunately, the problem is a relatively rare one. Indeed, on any given day, more than 87,000 flights are in the skies in the United States, according to statistics from the National Air Traffic Controllers Association. But last year, United States health officials barred a grand total of just 33 tuberculosis-infected people from flying.
And even if you happen to be sitting near a fellow passenger who has tuberculosis, the risk of transmission remains fairly small.
"I think that frankly -- and fortunately -- the risk is close to zero for transmission," Schaffner said. "These are extremely unusual events, and even when [health officials] have followed up, they almost never find any cases of transmission."
"The actual number of people that get tuberculosis on airplanes is probably infinitesimal compared to the thousands of people who travel on an airplane every year," he said.
If you are concerned that a nearby passenger has tuberculosis -- or, in fact, any respiratory infection -- you might do best to try to move as far away as possible.