The NHS said the patient had no underlying health conditions
A patient in Essex has become the first person in the UK without underlying health problems to die of swine flu.
NHS East of England said the victim died at Basildon and Thurrock University Hospital on Friday.
A spokesman said the hospital trust "would like to extend their deepest sympathies to the family affected as they come to terms with their loss".
On Thursday the government said 14 people were thought to have died in the UK after contracting swine flu.
England's chief medical officer Sir Liam Donaldson said not all of those had died as a direct result of swine flu but they had all had the virus.
Of the 14 deaths, 12 occurred in England and two in Scotland.
Sir Liam Donaldson: "We can't be complacent about this virus"
The number of swine flu cases in London and the West Midlands was approaching epidemic levels, he added.
Virology expert Professor John Oxford, of Queen Mary's College of Medicine in London, said the death was to be expected and should not cause panic.
"We've all been gritting our teeth, waiting for this to happen, and now it has. This doesn't necessarily mean the virus has mutated.
"Whether more patients with no underlying health problems die of the disease really depends on what the virus does next."
He added: "As the virus moves through the community you'll get some people who have no symptoms, some who have mild symptoms, some who get very ill and some who die, including those without any underlying health problems."
BBC News health correspondent Branwen Jeffreys said: "This was someone with no previous health problems, but not perhaps surprising.
"Although this flu virus has been fairly mild in most people there is always the possibility with flu that it can be a severe illness."
At the request of the patient's family no further details about the victim will be released by the health service.
Dr Andrea Atherton, director of public health for NHS South East Essex, said: "We would like to reassure people that the risk of transmission still remains small.
"It is important to stress that the symptoms of swine flu are, relatively speaking, mild.
"Unless you have flu-like symptoms and are being tested for swine flu, there is absolutely no need to stop your normal everyday activities."
Two people in Canvey Island are being treated for a mild form of swine flu and the East of England has seen 14 cases overall, a spokeswoman said.
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