A patient from London has died after contracting swine flu, reports suggest.
The death brings the number of people who have died after being diagnosed with the H1N1 virus to 16.
The news follows the announcement one of the Gordon Brown's advisers has contracted the virus.
Michael Jacobs, the prime minister's senior aide on climate change, is thought to have contracted swine flu during a recent visit to Mexico.
He is not believed to have had any direct contact with Mr Brown since developing symptoms two weeks ago.
He was, however, required to stay away from the G8 summit in L'Aquila in Italy last week for fear he could spread the virus.
A Downing Street spokesman said: "There has been extensive preparation in Downing Street and across the civil service to minimise the spread of swine flu.
"The Cabinet Office has issued guidance to personnel managers in all departments and comprehensive information is available to civil servants on how to deal with suspected cases."
The government recently announced action was now being taken to move away from a policy of containment to one of treatment.
There are also plans to vaccinate every person in the UK with predictions the virus could become more dangerous through the autumn and the winter.
Health secretary Andy Burnham recently declared there could be up to 100,000 new cases diagnosed every month.
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