Two more patients have died after being treated for diarrhoea and vomiting at the Royal Alexandra Hospital in Paisley.
The deaths are being linked to the vomiting bug norovirus, which killed two patients at the hospital last week.
NHS Greater Glasgow and Clyde said both patients died due to their underlying medical conditions although diarrhoea and vomiting was a contributory factor in one of the deaths.
Consultant microbiologist Dr Teresa Inkster said: "Our deepest sympathies are with the families at this time.
"Strict infection control measures are in place throughout the hospital and I would like to remind hospital visitors of the importance of hand hygiene when entering and leaving hospital premises.
"Norovirus is particularly prevalent virus common in the community and healthcare settings. Typically it has a sudden onset and can spread quickly and therefore we would urge relatives and any visitors who have experienced any symptoms of diarrhoea or vomiting within the last forty-eight hours not to visit the hospital.
"We would also ask that visitors are restricted to close family and friends whenever possible due to the current situation."
Two further wards are now not admitting patients due to an increase in the number of patients with diarrhoea and vomiting, thought to be norovirus.
This brings the total number of wards affected to eight, while a total of 34 patients are now showing symptoms of the virus.
Outwith the wards affected, the hospital continues to run as normal. Patients who have outpatients appointments or have a planned hospital admission are being told they should attend these as normal.
Meanwhile, NHS Highland has shut three hospital wards over concerns about staff and patients catching the bug.
Two wards at Raigmore hospital in Inverness have been closed to new admissions and one ward at Caithness general hospital in Wick has also been shut. In total, 37 patients and 23 staff are affected at the two hospitals.
For more information on norovirus, visit the STV Health Centre, brought to you by NHS inform.
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