More tests will be conducted to see if the norovirus behind recent outbreaks has mutated, the Centre for Health Protection's Dr Raymond Yung says.

He said today 22 outbreaks were recorded in public hospitals in May and June, affecting 165 people, including 28 staff. Fifty confirmed norovirus outbreaks in elderly homes affecting 699 people have also been reported. The cases suggest the virus, which was common in winter and spring in the past, is now also active in summer.

Unlike past cases which affected mostly children and had vomiting as the most common symptom, those affected in recent outbreaks are usually the aged and their most common symptom is diarrhoea.

In the first four months of this year, there were19 and seven outbreaks in elderly homes and hospitals, affecting 295 people.

Ninety-nine noroviral gastroenteritis outbreaks in institutions, including childcare centres and schools, involving 1,301 people have been reported in the first half of this year. Last year saw 42 norovirus outbreaks in institutions, affecting 643 people.

Dr Yung said initial tests showed the genetic sequence of the virus is different from the one found in the past, adding that more tests are required to confirm any mutation. He urged people to see a doctor if they have norovirus symptoms. For more information click here.

Daily alert

Hospital Authority staff are on alert for gastroenteritis cases and infection control measures have been enhanced. A daily alert on new institutional outbreaks will be sent to all public hospital infection control teams. Talks on precautionary measures will also be held for staff of elderly homes and private practitioners.

As at 5pm today, there are five public hospitals - Pamela Youde Nethersole Eastern, Castle Peak, Tai Po, North District and Prince of Wales - with new cases of patients and staff suffering from diarrhoea or vomiting symptoms, involving 18 patients aged 10 to 85 and four staff. All the patients are being treated in isolation, while the staff concerned are on sick leave. Their condition is stable.