The Chief Medical Officer Sir Liam Donaldson has warned to expect more deaths from swine flu, but has insisted such cases will remain rare unless the virus mutates.
Photo: ANDREW CROWLEY
Sir Liam's comments come after the first British patient without any underlying health problems to die after contracting the disease.
The patient died on Friday at Basildon and Thurrock University Hospital NHS Foundation Trust, taking the total number of UK swine flu-related UK deaths to 15.
In the other 14 cases, the people had underlying health issues such as heart problems and long term illnesses.
The family of the latest victim has asked no details of their relative be released.
Sir Liam said that while more deaths could be expected, those in normally healthy individuals would be extremely rare.
He said: "Fortunately, this particular new virus isn't nearly as severe as it could have been," he told BBC Radio 4's Today programme.
"If it had, for example, come out of the bird flu variant it would have been producing much higher levels of mortality."
He said that in the worst case scenario, the virus could combine with another flu virus – such as bird flu – to form a completely new variant, although that was unlikely to happen.
"That is a possibility. It is not a very likely scenario, but it is the worst case scenario," he said.
"This death underlines that, although the virus is proving generally mild in most people, it is more severe in some cases.
"As with all flu-like viruses, some people are at higher risk than others. Unfortunately, people who are otherwise healthy could also become seriously ill or, sadly, die."
The Essex patient may have died from the virus moving deep into their respiratory tract and into the lung, followed by an infection of the lungs by a bacterium, he added.
This would result in breathing difficulties and pressure on the heart.
There are at least 9,718 confirmed cases of swine flu in the UK – third highest in the world after Mexico, where the bug was first identified, and the US.
Mexico has 10,262 cases of the disease, with 33,902 in the US.
It is not known how many people in the UK are truly suffering from swine flu as many are treating themselves at home rather than contacting their GP.
The number of cases in London and the West Midlands, however, are said to be approaching epidemic levels in terms of the number of cases being reported.
Professor Steve Field, chairman of the Royal College of General Practitioners, said the latest death should not lead to panic.
"This doesn't change things at the moment," he said. "We would expect a certain number of deaths. I'd have expected a death with no underlying causes to have happened earlier.
"It doesn't change anything we're doing."
John Oxford, Professor of Virology at Queen Mary's College of Medicine in London, said the latest death of an otherwise healthy individual was to be expected and did not give any extra cause for concern.
He said: "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."
The NHS advises anyone who thinks they might have flu to check their symptoms on http://www.nhs.uk or call the swine flu information line on 0800 1 513 513.