NHS Lothian has closed six wards to visitors at Edinburgh Royal Infirmary after an outbreak of norovirus.

Nearly 100 people have been treated at the hospital with the illness, known as the winter vomiting bug, since the start of February.

Wards 101, 102, 103, 201, 202 and 207 are currently closed to visitors with relatives and friends of patients in affected wards advised not to visit in a bid to halt the spread of the outbreak.

Consultant virologist Dr Kate Templeton, chair of the problem assessment group at NHS Lothian, said: "By restricting the number of visitors it is hoped this will reduce the number of people who are exposed to norovirus and therefore shorten the duration of the outbreak."

NHS Lothian introduced similar restrictions when more than 150 patients and at least 17 members of staff were struck down by the bug at Liberton Hospital, Edinburgh, in January and February.

Professor Alison McCallum, director of public health and health policy at NHS Lothian, said the Liberton Hospital moves "proved effective in helping to prevent the further spread of the virus on the site".

She added: "Our priority is always patient, public and staff safety. While we understand that this tem-porary visiting restriction may cause some frustration, this measure will allow us to help prevent further spread of the infection and ensure safe patient care.

"We understand there may be extenuating circumstances where members of the public need to visit loved ones, such as if they are seriously ill. If this is the case, relatives or friends are asked to call ahead to the ward to arrange visiting. Clinical and nursing staff are working very hard to minimise any distress and discomfort to patients."

NHS Lothian said infection prevention and control staff are monitoring the situation and it hoped the wards will re-open to visitors in the very near future.