A handful of Republican staff members in Cleveland for the GOP convention were reported to be suffering Tuesday from a possible norovirus infection.

And if there are a few people with norovirus, it’s likely there will be more.

As many as 11 members of the California delegation’s advance team are showing symptoms that are consistent with the norovirus, according to Peter Schade, the Erie County health commissioner, who is investigating the outbreak. They are staying at a hotel in Sandusky, Ohio, about an hour from

“We’ve got about 11 who have been sick over the last few days, and we’ve been out there every day and working with them to eliminate the spread [between] the resort and the delegation from California,” Schade said.

The health department is running tests to confirm whether the Republican staff members have norovirus.

Noroviruses trigger explosive bouts of vomiting and diarrhea. They clear you out and clear out of your system pretty quickly. Symptoms typically only last one to three very miserable days. Most people recover without incident, but some people may need medical care for dehydration—especially small children or older adults.

The pesky bugs are exceedingly contagious. Norovirus outbreaks rip through crowds, and are often associated with travelers on cruise ships, children in day care centers, or guests at a wedding.

Jim Brulte, the California delegation chairman, told STAT in an email that the trouble started when one of the staff members who arrived ahead of the delegation came down with a virus and infected her husband.

He said the staff members who are showing symptoms are being quarantined until they’ve gone at least 24 hours without showing symptoms.

“To the best of our knowledge,” Brulte said, delegation staff members were the only people affected.

The hotel where the staff members are staying has a large indoor water park—the sort of environment in which the virus could thrive.

Brulte said the delegation has added hand sanitizer stations at the Sandusky hotel and that the executive director has sent an email to the delegates advising them on precautions to take. He added, however, that some delegates and alternates are staying at two other locations in the area.

Norovirus spreads via what’s called the fecal-oral route. That’s a not-so-appealing way of describing how virus that has come out of one person finds its way into another.

Caring for or cleaning up after someone who has had a norovirus infection can trigger a new infection. Even touching surfaces that are contaminated with noroviruses and then later putting your fingers in your mouth will do the job.

Eating food prepared by people sick with norovirus infections can induce infection. In fact, the Centers for Disease Control and Prevention says noroviruses are the leading cause of illness and outbreaks from contaminated food in the US.

A little over a decade ago, when two employees of a Massachusetts bakery worked while ill with norovirus-like symptoms, norovirus outbreaks occurred at 46 weddings on a single weekend. The source of infection: wedding cakes. Up to 2,700 people were affected, a report of that outbreak revealed.

David Nather contributed reporting.

Republished with permission from STAT. This article originally appeared on July 19, 2016.