At today's briefing she warned the highly-transmissible Omicron variant is likely to overtake Delta as the dominant strain in Scotland within just days.
Ms Sturgeon said as from tomorrow household contacts of people with any Covid should isolate for 10 days whether or not they are vaccinated and she backed Public Health Scotland advice urging people to cancel Christmas parties due to the rising number of cases.
There was a total of 109 Omicron cases in Scotland yesterday, which has risen from just nine since November 30 when it was first detected here.
Latest Covid numbers showed 573 people in Scotland are in hospital, 40 people are in intensive care and 19 more deaths have been reported.
Rising cases could also put significant additional pressure on hospitals and other health and care services this winter when they are already under pressure.
In her briefing she said Omicron was more capable of infecting people who have previously been infected and that vaccines may be less efficient in fighting the virus, adding it is not known yet if that strain of virus causes more, or less, serious illness.
She urged people to be sensible and defer Christmas parties, keep testing before meeting others - even for festive shopping trips - and get vaccinated.
Ms Sturgeon added she was not trying to 'scare' people but wanted to provide context for difficult decisions that the Government might need to take in days to come.
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