The Centre for Health Protection is monitoring the situation of viral gastroenteritis caused by rotavirus and norovirus, as Hong Kong enters the high season for the illness which peaks December to February.

The centre's controller Dr Thomas Tsang today said there was a rise in rotavirus and norovirus activity in December as seen by the number of gastroenteritis outbreaks in institutions.

"Twenty-one institutional outbreaks of acute gastroenteritis have been reported so far this month, compared with six in November and four in October," he said. "Seven out of the 21 outbreaks were due to norovirus, affecting 62 persons, while one outbreak, affecting five, was due to rotavirus."

He said the consultation rate of acute diarrhoeal diseases among general practitioners has also increased this month.

"The latest consultation rates for acute diarrhoeal disease were 33 and 35 cases per 1,000 consultations in the week ending December 20 and December 13, compared with 19.8 to 27.7 in the preceding four weeks," Dr Tsang said.

80 cases this year

A total of 75 norovirus gastroenteritis and five rotavirus outbreaks respectively involving 677 and 39 people have been reported so far this year. Last year there were 107 norovirus outbreaks affecting 1,211 people and six rotavirus outbreaks affecting 46 people.

Rotavirus infection causes vomiting and diarrhoea for several days. Fever and abdominal pain are also frequently reported.

Dr Tsang said: "For healthy people, rotavirus gastroenteritis is a self-limited illness. However, it is occasionally associated with severe dehydration in young children. Immunity after infection is incomplete, but re-infections tend to be less severe than the original infection."

Norovirus infections are usually mild and self-limiting. Symptoms include nausea, vomiting, diarrhoea, abdominal pain, fever and malaise. The infection can spread through the consumption of contaminated food or direct contact with infected people.