Feb. 25, 2005 — -- Taking a cruise evokes sun, fun, fine dining, relaxation and romance -- the ingredients of a perfect vacation.
But also lurking on these ships in places you can see -- and places you cannot -- may be a cast of stowaways that could potentially ruin your holiday.
Most notable among them is the norovirus, a nasty bug that can cause a couple of days worth of severe nausea, vomiting, diarrhea, fatigue and headaches. The norovirus can spread easily when large groups of people are gathered together in close proximity, places like restaurants, schools, nursing homes, hotels -- and cruise ships.
Last month alone, there were seven norovirus outbreaks on cruise ships.
ABC News' "Primetime Live" sent teams of producers equipped with test tubes, gloves and special lights on four different cruise ships.
They did not find any norovirus. But they did find other things that were disgusting, though not actually dangerous to your health -- dried semen and urine on blankets, furniture and walls in each of the cabins in which they stayed.
For example, on one cruise ship headed to the Bahamas, an ultraviolet lamp exposed dried urine by the door handle and on the vanity stool. Dried semen was on the carpet and on the blanket. The cabin cost nearly $2,000 a week.
Dr. Aaron Margolin, a leading microbiologist and viral expert at the University of New Hampshire who consults for the government, told ABC News he thinks such stains are not uncommon on cruise ships or in hotels and motels. "I think what's new is that we have new ways of detecting it so that we now know that it really exists," he said.
In fact, "Primetime Live" found similar results two years ago when it swabbed for stains in hotel rooms in establishments ranging from one-star to five-star. All 20 rooms had urine or semen stains on bedding, furniture or walls -- in one room, on the Bible.
"I think when an individual goes to a hotel, motel, a cruise ship, they expect that the area is sanitarily disinfected. I think what they have to realize is that is not the case," Margolin said.