The flu rate in Scotland for the first week of 2018 was four times higher than the same week last year.
Statistics from Health Protection Scotland showed 107 Scots in every 100,000 of the population were diagnosed with the virus in the week ending January 7.
It marks an increase from 46 people per 100,000 in the last week of 2017, and is four times higher than the figure recorded in the first week of last year, when 24.6 people in every 100,000 had the virus.
Health Secretary Shona Robison said the NHS was coming under "significant pressure" as a result of higher flu levels and thanked staff for doing "a remarkable job".
She said: "These statistics confirm what we've been hearing up and down the country that the complexity of treating flu, including appropriate diagnosis and segregation to avoid cross-contamination, is putting our health system under significant pressure.
"Emergency departments saw the highest level of attendances over the festive period in a number of years - during the two-week festive period attendances were up 10% compared to the previous year, with a 20% rise in the week leading up to Christmas.
"Despite these challenges, over 82% of patients were still seen within the four-hour target in Scotland's core A&Es throughout December, compared to 77.3% in England."
Meanwhile, it emerged that an 18-year-old woman has died of pneumonia in Scotland after suffering from a flu virus.
Bethany Walker is understood to have been airlifted to Raigmore Hospital in Inverness after becoming ill.
Ms Walker, reportedly from Applecross in Wester Ross, died on Friday January 5, despite the best efforts of medics.
The Applecross Inn paid its own tribute to her on its Facebook page.
It said: "Farewell to dear Bethany another fantastic member of our team who we sadly lost last Friday after a short illness, you were the 'belle of the ball' at Hogmanay ... and indeed everywhere.
"Such a tragic loss of someone so perfect in every way, so polite, such beauty, humour, fun, music and studies.
"You were pure pleasure as an employee ... loved by every member of our team, so much devotion and dedication to all you did."
Scotland's Deputy Chief Medical Officer Dr Gregor Smith has encouraged people eligible for free vaccination - including the elderly, young children, mothers-to-be and health workers - to ensure they are protected from the disease.
He said: "While we've still got a couple of months of winter left, this week's statistics provide further evidence that the vaccine is a good match against the current most common strains.
"I would encourage anyone in an eligible group to get vaccinated - it is the best defence against flu.
"The best way to stop the spread of flu is to follow simple hygiene practices. Wash your hands often with warm water and soap, use tissues to trap germs when you cough or sneeze, and bin those tissues as quickly as possible."
Ms Walker left Plockton High School in the summer of 2017 to take a gap year before studying midwifery in Aberdeen.
The school said on Facebook: "It was a privilege for all of us to have taught Bethany, to have known her in her years in the school and to have maintained contact with her after she left.
"It is tragic to lose someone so young and the thoughts of the whole school and the hostel are with Bethany's family at this sad time."
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