Schools and childcare centres have been issued a third health advisory warning them to be alert to a virus that causes severe dehydration in young children and kills hundreds of thousands globally each year.
The Department of Health's Centre for Health Protection action comes ahead of the resumption of schools next week after the Christmas holiday.
Thomas Tsang Ho-fai, controller of the centre, said there had been a sharp increase in cases of gastroenteritis, with 21 institutional outbreaks - 11 at childcare centres and one at a primary school - reported so far this month, compared with six last month and four in October.
One outbreak was found to be due to rotavirus, which alarms the World Health Organisation because globally every year it kills 527,000 children under the age of five.
'For healthy people, rotavirus gastroenteritis is a self-limiting illness,' Dr Tsang said yesterday. 'However, it is occasionally associated with severe dehydration in young children. Immunity after infection is incomplete, but reinfections tend to be less severe than the original infection.'
David Sniadack, a medical officer at the WHO's Western Pacific Regional Office, said: 'Rotavirus infections appear to occur in both developed and developing countries.'