Federal health officials boarded a cruise ship in Halifax on Friday to assess efforts to contain a suspected outbreak of norovirus.

The Caribbean Princess arrived Friday morning for a nine-hour visit to the city.

Of the 4,250 people aboard, 105 passengers and three crew members had symptoms such as diarrhea and vomiting, said the cruise line company Princess Cruises.

This pattern "strongly suggests" that a norovirus is the cause, the company said in a media release.

Noroviruses, including Norwalk, affect the gastrointestinal system with symptoms that include diarrhea, abdominal cramps, nausea and vomiting. The virus can be passed to other people up to two days after symptoms disappear.

"I've been on board where some people have been sick occasionally, but not to this extent," said passenger Helen Hunt, who said she has taken 54 cruises with the Princess line. Hunt was among the many passengers who got off the ship as planned.

Security guards wore rubber gloves as they helped people returning to the ship. Passengers were told to disinfect their hands.

Dr. Robert Strang, Nova Scotia's chief public health officer, said it is not unusual to find a norovirus on a cruise ship because of its confined environment.

"I know the cruise ship industry takes this issue seriously and is taking significant steps in controlling this, in terms of cleansing of ships and all those kinds of things," he said.

Strang said the cruise line notified Health Canada about the situation before arriving, as required under federal rules.

He said there was at least one cruise ship in Halifax carrying a norovirus already this season.