The Seattle Yacht Club is closed until Tuesday or possibly longer, because of an outbreak of norovirus.

The Seattle Yacht Club’s main clubhouse will be closed until Tuesday, or possibly longer, because of an outbreak of norovirus.

Club officials became aware of the virus outbreak March 1.

Club commodore Kim Lorenz said Thursday that at least 150 people became ill because of the outbreak. A few people have been briefly hospitalized. He said the club will spend eight days sanitizing the facility on East Hamlin Street before deciding whether it’s safe to reopen.

People attending a party celebrating someone’s 100th birthday Feb. 25 were the first to fall ill from the virus, Lorenz said. The guest of honor was among 40 of the 60 people at the party, mostly elderly, who came down with the virus.

It was followed by the JO Ball on Feb. 26, where people also became sick. The club scrubbed the facility clean and reopened, but more people became sick last weekend, so the club decided to close it again and re-sanitize it. Lorenz said he had dinner at the club frequently, but he never became ill.

He said the club has no idea how it became infected, but suspects it was food contamination, and the focus is on lettuce. The club was throwing away all its food, even salt and pepper.

Lorenz said one employee who was ill, but then returned to work, could have passed on the virus.

“I doubt we’ll ever know,” he said.

Lorenz said while people were reported sick, it wasn’t until Tuesday that Public Health — Seattle & King County determined it was norovirus. He said the club has received assistance from many people on how to deal with the virus, including cruise-ship companies. Norovirus has been a problem on cruise ships.

“Until the virus has had a chance to run its course and we can once again sanitize all surfaces, I feel we need to take a very cautious and conservative approach,” the club’s general manager, Steve Hall, wrote in a message on the club’s website.

He pointed out that it’s not food poisoning, but a virus that is spread through food as well as human-to-human contact.

Norovirus causes severe gastrointestinal distress that usually lasts 24 to 48 hours. It is particularly dangerous for the elderly.

The virus is contagious as long as 72 hours after an individual is symptom-free, Hall wrote, but it can last on items touched for up to 12 days.