The 45-year old from Paisley is one of two new critical cases being treated in intensive care at the Royal Alexandra in Renfrewshire.
The other is a 38-year-old woman who has underlying health problems.
One of the new cases is a 26-year-old staff nurse from the Southern General Hospital, Glasgow, who cared for the 38-year-old woman currently in intensive care.
As a result of this, hospital staff are now being asked to treat anyone with symptoms of diseases like pneumonia as a confirmed case until they are proven negative.
A total of 18 further patients in England have tested positive with swine flu. Together with the 23 cases in Scotland announced on 2 June by the Scottish Executive and one in Northern Ireland this brings the current total of confirmed UK cases to 381.
The surge in cases has prompted calls for the WHO to raise the alert level to phase six, indicating a full pandemic.
Latest figures from the WHO show that 66 countries have officially reported 19,273 cases of influenza A(H1N1) infection, including 117 deaths.
However, the WHO has not indicated that the alert level will be raised.
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