Twenty-one residents of a Hong Kong child care center have fallen ill as the H1N1 virus continues to rage in the city, with 17 of them already tested positive for the disease, health officials said on Wednesday.

The fifteen boys and six girls from the residential child care center in Causeway Bay came down with fever, cough and sore throat since August 9, a spokesman from the city's Center for Health Protection said, adding that all the 21 patients, aged between six to 15, are now stable and no hospitalization is required.

The Center for Health Protection is still investigating the outbreak, the spokesman said.

Hong Kong reported 345 new cases of H1N1 by Wednesday, bringing the total tally to 7,906 since the virus was first detected at the end of May.

Hong Kong, with a total population of 7,008,300 in mid-2009 including 6,797,300 usual residents and 211,000 mobile residents, has five H1N1 cases in every 10,000 residents.

Experts from World Health Organization (WHO) had predicted that the pandemic may last for one or two years, with one third of the world's population infected.