NEW YORK (CBS) - Cruises can be packed with passengers in close quarters, raising the potential for infectious diseases to spread like wildfire if anyone on board gets sick.
A gastrointestinal illness outbreak has been making its way through the Royal Caribbean Explorer of the Seas cruise ship, infecting more than 20 percent of passengers since it left a New Jersey port on Jan. 21. As of Jan. 29, 630 of the 3,071 passengers on board were reporting symptoms, predominantly vomiting and diarrhea. More than 50 crew members also got sick, according to the Centers for Disease Control and Prevention’s Vessel Sanitation Program.
The 10-day journey had to be cut short given the illnesses outbreak, and the ship returned home to Cape Liberty, N.J., Wednesday afternoon around 2:00 p.m. ET.
The CDC points out despite good cruise ship environmental health standards and surprise investigations conducted twice yearly by the Vessel Sanitation Program, outbreaks of gastrointestinal illness persist on ships.
While the CDC has yet to confirm the source of the illness -- tests are pending and will be released later in the week -- the most common culprit is norovirus.
Up to 21 million cases of norovirus occur in the U.S. each year, resulting in up to 70,000 hospitalizations and 800 deaths. It’s caused by a highly contagious virus, explains CBS News chief medical correspondent Dr. Jon LaPook, and spreads via microscopic particles found in feces and vomit from infected people.
If a person has infectious diarrhea from norovirus, they may excrete billions of disease-causing particles, he pointed out. But it only takes about 18 virus particles on average for another person to get infected.
“So you only need a little bit of infection,” he said.
Compounding the spread of the disease, people may be contagious before they show any symptoms. Norovirus typically has an incubation period of 12 to 48 hours. Then days later, they may finally experience vomiting and diarrhea.
“You just feel lousy,” said LaPook. “It can be really brutal.”
Norovirus can remain present in feces for two weeks and continue to spread infection even after a person feels better.
That’s why prevention is so important.
Make sure you wash your hands thoroughly with soap and water, especially after using the toilet or changing diapers, and always before you prepare or handle food. That is especially important advice, since norovirus can linger after people have recovered.
If you’re preparing a meal, wash fruits and vegetables thoroughly. Since noroviruses are relatively resistant microbes, cook seafood to 140 degrees Fahrenheit.
If you are sick, do not prepare food or care for others. Launder soiled items carefully -- the CDC recommends wearing disposable or rubber gloves.
“If you have symptoms of norovirus, the most important thing is hydration," says LaPook, who added that chicken soup with rice can help in a situation like this. Fluids with electrolytes may also help prevent dehydration.
“Stay hydrated. Stay inside. Stay away from other people -- don’t be hugging other people and giving them the infection,” he advised.
Norovirus symptoms can sometimes be confused with food poisoning from eating something that contains toxins because food was not stored at the proper temperature. But in that case, a person would normally start feeling ill within hours after eating, because symptoms are caused by toxins. Norovirus, on the other hand,