HONG KONG, March 26 (Reuters) - Hong Kong will resume classes for schoolchildren next week after scientists confirmed that seasonal flu viruses circulating in the city had not mutated to become more vicious, public health officials said on Wednesday.

The outbreak had no links to H5N1 bird flu, but the decision to shut schools brought back memories of 2003, when an outbreak of Severe Acute Respiratory Syndrome (SARS) hit Hong Kong.

"After virological analyses, we found that the viruses had not mutated. They are the same viruses that are prevalent this season, the genes are the same and there is no sign to say this is a (more) vicious virus," Thomas Tsang, controller of the Centre for Health Protection, told a news conference.

Hong Kong shut elementary schools for two weeks in mid-March to contain a seasonal influenza outbreak after two children who contracted the flu died.

But experts later said they found no evidence that the children had been infected by virus strains that were more virulent or aggressive, which opened up the possibility that their deaths might have been linked to other causes.

"Six students had severe complications resulting from flu in the last two weeks ... the figure is more or less average and it goes to prove we are not seeing (a rise in) serious admission cases because of the flu season, so we are confident we can resume classes on 31st of March," Tsang said. (Reporting by Tan Ee Lyn; Editing by Alex Richardson)

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