A number of members of the California delegates' staff at the Republican National Convention in Cleveland have fallen ill with norovirus, according to news reports.

The highly contagious stomach virus is the same type of virus that is well-known for ruining cruise vacations.

Norovirus spreads very easily, especially at close-quarters events like conventions and cruises, said Dr. Amesh Adalja, an infectious-disease specialist and a senior associate at the University of Pittsburgh Medical Center's Center for Health Security. [7 Devastating Infectious Diseases]

The virus causes vomiting, and the vomit is infectious, Adalja said. If a person comes in contact with a surface that has vomit on it, or that was not completely cleaned after having vomit on it, that individual can get sick, Adalja said.

The symptoms of a norovirus infection come on very quickly and dramatically, Adalja said. A person can go from feeling fine to suddenly vomiting, he said. Because of that, vomit gets in places that it shouldn't, he said. That is, a person may not to make it to a sink or toilet, he added.

In addition, the virus can survive for days outside of the body, so to become infected, a person doesn't necessarily need be near a person who is actively vomiting, but rather just in area where the vomit is or was, Adalja said.

The virus also spreads via stool and saliva. It's common to find the virus on infected people's hands because they touch their mouths, Adalja said. And alcohol-based hand sanitizers aren't very effective at killing norovirus, Adalja told Live Science. People need to be meticulous about washing their hands, he said.

The infected members of the California delegation were isolated from other people at the convention, USA Today reported.

Indeed, you have to quarantine people who are infected with norovirus, Adalja said. "Actively sick people need to be removed from the general public and should minimize contact with" healthy people, he said. Sick people will just continue to "shed and spread" the virus everywhere, he said.

And though symptoms last only about 24 to 48 hours, people can still shed the virus after symptoms have passed, Adalja said. The best way to avoid infection is to wash your hands well, Adalja said. And if you see someone vomiting, go in the other direction, he said.

Originally published on Live Science.