Health officials have issued a warning over soaring levels of the winter vomiting bug across Scotland.
New figures from Health Protection Scotland (HPS) show that 50 patients were struck down with norovirus this week, compared to just 4 patients the week before.
Norovirus is highly infectious stomach bug, causing symptoms such as vomiting and diarrhoea.
In most cases it will pass after a few days but it can be dangerous in elderly patients and people who are already ill.
NHS Greater Glasgow and Clyde closed two wards at the same hospital to prevent the spread of the infection, which affected around 27 patients.
NHS Lothian has also closed a ward at the Edinburgh Royal Infirmary after 23 patients contracted the virus. It has since reopened.
Lisa Ritchie, a HPS nurse consultant, said: “To help reduce the risk of outbreaks in hospitals, care settings and the wider community, we are again asking members of the public who think they have norovirus to stay at home until at least 48 hours after any symptoms have stopped.
“As norovirus is so infectious, it is important that everyone plays their part in reducing the risk of outbreaks.
“To do this, hospitals may suspend access to particular wards to protect patients, staff and visitors from norovirus and to minimise disruption to healthcare services.”
Dr David Farquharson, medical director at NHS Lothian, said: “A number of patients at the Royal Infirmary of Edinburgh were previously displaying symptoms of Norovirus.
“We have strict infection control procedures in place and are managing and reviewing the situation on a daily basis, which has improved over the last few days.”
All wards have now reopened at the Royal Alexandra Hospital and the Glasgow Royal Infirmary, according to a NHS Greater Glasgow and Clyde spokesman.
The health board said: “In total, four wards have been closed recently due to Norovirus, three of which were at the Royal Alexandra Hospital and one at the Glasgow Royal Infirmary. There have been a total of 36 patients affected and 15 confirmed cases amongst our staff.
“Wards with patients showing symptoms do not admit new patients as a precautionary measure and the wards are closely monitored with strict infection control measures in place. The management of these ward closures is fully in line with national infection control protocols.