About 225 passengers on the Norwegian Cruise Line ship Pride of Hawaii were infected with norovirus, a highly contagious stomach flu, according to media reports Wednesday.

For a seven-day voyage, passengers were aboard the ship on Nov. 5, with nine percent of whom reporting to the medical center Tuesday with symptoms of nausea, stomach cramps and mild diarrhea.

After the ship docked back in port in Honolulu, immediate laboratory tests were carried out in the Hawaii Department of Health. Janice Okubo, the department's spokesman, announced that there were no doubts as to the origination of the disease.

In January, 300 passengers aboard the Queen Elizabeth II came down with the norovirus just before the ship docked in Honolulu.

In June last year, 60 passengers aboard NCL's Pride of Aloha got sick.

And in February 2003, 300 passengers and crew members aboard the Sun Princess got sick.

Norovirus or Norwalk-Like Virus (NLV), which sometimes is called stomach flu or gastroenteritis, can be classified as a group of viruses among which there can be singled out at least five genogroups: GI, GII, GIII, GIV and GV, and each group has at least 30 subgroups.

It is called Norwalk-Like Virus after an outbreak at an elementary school in Norwalk, Ohio, in 1968 and is considered to be a highly contagious germ, by the Centers for Disease Control of U.S. 

It is a kind of infectious disease, outbreaks of which can be viewed in many public places such as nursing homes, schools, cruise ships and hospitals.

(Agencies via Xinhua November 14, 2007)