Bathing suit? Check. Suntan lotion? Check. Nose spray to keep diarrhea from ruining your cruise?
It's not on the checklist yet, but scientists are closing in on a nasal vaccine that would protect against norovirus, the virulent bug that is the curse of cruise ships, cheerleading competitions and any other venue that brings large numbers of people into proximity.
With an estimated 20 million infections a year nationwide, norovirus is the No. 1 cause of the intestinal crud people call stomach flu.
"This virus is very democratic," said Jan Vinje, of the U.S. Centers for Disease Control and Prevention. "It affects everyone."
If the research goes well, the vaccine could be available within five years, said Charles Arntzen, a molecular biologist at Arizona State University.
"We are going to have a vaccine," he said recently at the annual meeting of the American Association for the Advancement of Science. But it's not clear how effective a vaccine would be against a virus that evolves rapidly and comes in more than 30 varieties. And how many people will be willing to get vaccinated for a disease that's generally just a nuisance?
Cruise ships and community outbreaks get most of the publicity, but nearly 60 percent of norovirus cases occur in nursing homes, Vinje said. Cruise ships account for 4 percent, and another 4 percent are linked to schools and school events. Children and adults are equally vulnerable.
Most victims recover after a day or two of misery, but more than 70,000 a year are hospitalized. The CDC estimates that the virus kills 800 people a year, most of them older than 65. The annual economic toll is about $2 billion in medical costs and lost productivity.
Norovirus spreads quickly and can be harder to kill than the monster in "Alien." Symptoms hit suddenly. Outbreaks often start when an infected person vomits in the corridor of a cruise ship. Tiny particles fly through air and land on surfaces. Even flushing the toilet after a bout of diarrhea or vomiting can suspend more droplets in the air.
The bug can also slip into the body via food, water or dirty hands. Once it does, as few as 18 virus particles are enough to do the trick, making norovirus the most infectious microbe known, Vinje said.
While many viruses are too fragile to survive long in the environment, noroviruses are encased in a BB-like shell that allows them to live for days or even months in some settings. One contaminated airplane cabin spread the disease to successive flight crews over several days.
Cruise ships have learned through experience that ordinary mopping isn't good enough. They now use bleach to disinfect every surface, including hand rails and poker chips.
The first experimental vaccine worked well in a test on 100 people last year, Arntzen said.A nasal spray is better than a shot because it more directly targets the respiratory tract and gut where the virus concentrates.